OBD-II Code U1814: Powertrain Wake-Up Circuit Fault

What Does U1814 Mean?

U1814 means your car's Body Control Module (BCM) tried to 'wake up' other computers, like the Engine Control Module (ECM) and Transmission Control Module (TCM), but detected a short circuit. The BCM sends a 12V signal to tell these modules to turn on when you start the car or request a remote start. This code indicates the signal wire is shorted to ground, preventing the modules from powering up and communicating with the rest of the vehicle.

Technical definition: The official SAE/ISO definition for U1814 is 'Powertrain Wake Up Communication Circuit' or 'Powertrain High Speed Communication Enable Circuit'. The Body Control Module (BCM) has detected a short to ground on the serial data communication enable circuit (often designated as circuit 5985 in GM schematics) when attempting to activate other modules. Subtypes like U1814-02 specifically confirm a short-to-ground condition.

Can I Drive With U1814?

No — Do Not Drive. Driving is often impossible. This fault directly causes a no-start condition or leads to the sudden failure of critical systems like the engine, transmission, and power steering. Loss of power steering creates an immediate safety risk due to the high physical effort required to steer the vehicle.

Common Causes

• Chafed or Shorted Wiring Harness (Very Common) — The wire carrying the 'wake-up' signal is the most common failure point. It rubs against metal brackets, the engine block, or ground studs, wearing through the insulation and causing a short to ground. GM TSB 18-NA-114 highlights known harness chafing points near the G100 ground stud.
• Faulty Body Control Module (BCM) (Common) — The BCM sends the wake-up signal and fails internally, causing it to send a faulty signal or incorrectly report a short circuit. GM TSB 20-NA-206 details a critical failure mode where a failing BCM causes a short that destroys the Power Steering Control Module (PSCM).
• Corroded or Damaged Electrical Connector (Common) — Connectors for the BCM, ECM, or wiring harness corrode from moisture and road salt, creating an unintended path to ground. On 2010-2017 Chevrolet Equinox models, the X411 connector under the rear of the vehicle is a documented failure point.
• Internal Failure of a Connected Module (ECM, TCM, PSCM) (Less Common) — A receiving module (ECM, TCM, or PSCM) fails internally and creates a short circuit that pulls the entire wake-up line down. This prevents any other modules on that circuit from communicating.
• Blown Fuse (Uncommon) — A short to ground in the wake-up circuit blows a related power feed fuse (e.g., fuse F6DA on GM models). Replacing the fuse without fixing the underlying short causes the new fuse to blow immediately.
• Damage from Previous Repairs (Uncommon) — Wiring harnesses get pinched or improperly reconnected during unrelated service, such as a transmission replacement. A pinched harness between an instrument panel bracket and the body causes immediate communication DTCs.
• Improperly Installed Aftermarket Accessories (Rare) — Aftermarket remote starters or alarms improperly tapped into the vehicle's electrical system short the communication bus or its power supply.

Symptoms

• Engine will not start or crank — If the ECM doesn't receive the wake-up signal, it remains powered off, resulting in an immediate no-start condition.
• Loss of power steering and 'Service Power Steering' message — The Power Steering Control Module (PSCM) shares this network. If it fails to wake up, the vehicle loses power steering assist, resulting in heavy steering and a warning message.
• Multiple warning lights on the dashboard — The instrument cluster illuminates the Check Engine Light, ABS light, and AWD Fault messages alongside a flurry of loss-of-communication codes.
• Transmission stuck in one gear (Limp Mode) — If the TCM fails to wake up but the engine starts, the transmission defaults to a single gear (usually 2nd or 3rd) to allow limited vehicle movement.
• Scan tool cannot communicate with multiple modules (scan-tool only — no driver-felt sign) — A diagnostic scanner fails to connect to the ECM, TCM, or PSCM because they lack power. It only communicates with the BCM.
• Inability to clear codes (scan-tool only — no driver-felt sign) — After a BCM-induced failure, codes like U0100 latch into the PSCM. The scan tool displays a 'Rejected by control module' error when attempting to clear them until the hardware is replaced.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Repairing Chafed or Shorted Wiring — Parts: $10-$50, Labor: $250-$800, ~2.0-6.0 hr book time (Professional)
• Replacing the Body Control Module (BCM) and Reprogramming — Parts: $300-$700, Labor: $150-$400, ~1.5-3.0 hr book time (Professional)
  2019-2022 Chevy Silverado / GMC Sierra: OEM 13534086, 13535147, 13528941 (Alt: ACDelco (OEM Supplier))
  2010-2017 Chevy Equinox: OEM 13584695, 13580697, 13589324 (Alt: ACDelco, Dorman)
  2017-2022 Chevy Trax: OEM 13594571 (Alt: ACDelco (OEM Supplier))
• Replacing BCM and Power Steering Control Module (PSCM) — Parts: $1200-$2500, Labor: $400-$800, ~3.5-5.5 hr book time (Professional)
  2017-2022 Chevy Trax (per TSB 20-NA-206): OEM BCM: 13594571, Steering Column Kit: 42622461 or 42595687 (Alt: ACDelco (OEM Supplier))
• Repairing or Replacing a Corroded Connector — Parts: $20-$150, Labor: $150-$500, ~1.0-3.0 hr book time (Intermediate)
• Replacing a Faulty End-Module (ECM, TCM) — Parts: $600-$2000, Labor: $150-$400, ~1.0-2.5 hr book time (Professional)
  2018 Chevy Trax (1.4L ECM Example): OEM 12677671 (Alt: ACDelco, various remanufacturers)

DIY vs Professional

• Repairing Chafed or Shorted Wiring — Beginner:
  Tools: Flashlight, multimeter, wire cutters/strippers, solder, heat shrink, TESA tape.
• Replacing the Body Control Module (BCM) — Beginner:
  Tools: Basic hand tools for removal, manufacturer-specific software (e.g., GM SPS), and a compatible J2534 interface for programming.
• Replacing the Power Steering Control Module (PSCM) — Beginner:
  Tools: Extensive mechanical tools for steering column replacement, plus manufacturer software for programming and calibration (e.g., Steering Angle Sensor Learn).
• Replacing a Corroded Connector — Beginner:
  Tools: Connector depinning tools, terminal crimpers, wire strippers, new connector housing and terminals, or a pigtail connector kit.

Used vs. New Parts: Buying Guide

When a used part is worth it: A used BCM is only viable if you use a mail-in 'cloning' service. This is cost-effective if your original BCM still communicates, allowing its data to be copied to the used donor unit.

Donor-vehicle mileage cap: roughly under 100000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Part number must be an exact match or a known interchangeable number for a cloning service to work.
• Avoid modules from flood-damaged or fire-damaged vehicles.
• Ensure the seller offers a warranty and confirms the part is in working condition.

Decision logic:

• If Your original BCM is completely dead (no communication) → You must buy a new BCM and have it programmed by a dealer or qualified shop.
• If Your original BCM still communicates and you can handle vehicle downtime → A used BCM combined with a mail-in cloning service is the most budget-friendly option.
• If You need the vehicle repaired quickly and cannot wait for a mail-in service → Buy a new BCM and have it professionally installed and programmed.

Warranty tradeoff: Used BCMs from salvage yards typically have a 30-90 day warranty. Cloning services offer their own warranty on the programming. A new OEM BCM installed by a dealer includes a 12-month/12,000-mile parts and labor warranty.

Worst-case if a used part fails: $300-$500 if a used/cloned BCM fails. This includes the cost of another module, repeat labor, and potential re-cloning fees.

What Happens If You Wait — Timeline

1. 0-1 month: Intermittent Fault: A rare no-start or brief loss of power steering that resolves on the next key cycle. The code is stored but may not trigger a persistent warning light. The short is making momentary contact. (Added cost: $0. The only cost is a diagnostic fee ($150-$300) if you choose to investigate.)
2. 1-4 months: Frequent Intermittent Fault: The no-start or system failure happens more often (e.g., weekly). The vehicle is now unreliable and leaves you stranded. The intermittent short is becoming more consistent due to vibration or component degradation. (Added cost: $150-$300 (Towing and diagnostic fees become more likely).)
3. 4-6 months: Cascading Failure: The intermittent short, often from a failing BCM, sends voltage spikes that damage a connected module. Per GM TSB 20-NA-206, the PSCM is a common victim. The fault is now permanent. (Added cost: $1200-$2500 (Cost to replace the now-damaged PSCM/steering column in addition to the original faulty BCM).)
4. 6+ months: Permanent Hard Fault: The vehicle is in a constant no-start state. The original fault (wiring or BCM) has been active long enough that multiple modules on the wake-up circuit (ECM, TCM, PSCM) are potentially damaged, complicating the diagnosis and repair. (Added cost: $2000-$4000+ (Costs for extensive diagnostic time to trace the original short plus the replacement and programming of multiple control modules).)

Cost of Not Fixing It

• Immediate: Vehicle fails to start, leaving you stranded. Sudden loss of power steering occurs while driving, creating a severe safety hazard. (Added cost: $150-$300 (Towing and diagnostic fees))
• 1-3 months (intermittent fault): An intermittent short from a failing BCM sends voltage spikes through the wake-up circuit, destroying other modules connected to it, particularly the Power Steering Control Module (PSCM). (Added cost: $1200-$2500 (Cost to replace the PSCM/steering column in addition to the BCM))
• 3+ months: The intermittent fault becomes a permanent hard fault, resulting in a constant no-start condition. The risk of cascading module failure increases the longer the faulty BCM remains in operation. (Added cost: $2000+ (Multiple module replacements and complex diagnostic time))

Diagnosis Steps

1. Check for All Diagnostic Trouble Codes (DTCs)
   Use a professional OBD-II scanner to read all codes from all available modules. U1814 is almost always accompanied by a series of 'U' codes like U0100 (Lost Comms with ECM), U0101 (Lost Comms with TCM), and U0131 (Lost Comms with PSCM). Document all codes and their subtypes (e.g., -02 for short to ground).
   Tools: Professional OBD-II Scanner (Beginner)
2. Visually Inspect the Wiring Harness and Connectors
   Look for obvious signs of damage. Check areas where the harness routes near sharp metal edges, such as engine brackets, the transmission bell housing, and ground studs. Inspect key connectors like the BCM, ECM, and known problem connectors (e.g., X411 on Equinox) for corrosion, bent pins, or backed-out terminals.
   Tools: Flashlight, Mirror (Beginner)
3. Check Relevant Fuses
   Consult a vehicle-specific wiring diagram to identify fuses related to the BCM and wake-up circuit (e.g., F6DA on GM models). If a fuse is blown, it confirms a short circuit is present. Do not replace it yet, as it will blow again.
   Tools: Fuse puller or needle-nose pliers (Beginner)
4. Test the Wake-Up Circuit for a Short to Ground
   Disconnect the negative battery terminal. Disconnect the main connector at the BCM. Using a digital multimeter set to measure resistance (Ohms), place one probe on the pin for the wake-up circuit (e.g., circuit 5985 on GMs) and the other probe on a clean chassis ground. A reading near 0 Ohms confirms a short to ground. The reading should be infinite (OL).
   Tools: Digital Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
5. Isolate the Short by Disconnecting Modules
   If a short is confirmed, leave the BCM disconnected and unplug other modules on that same wake-up circuit one by one (e.g., ECM, TCM, PSCM). After unplugging each module, re-test the circuit for the short to ground from the BCM connector. If the short disappears after unplugging a specific module, that module has an internal short. If all modules are disconnected and the short remains, the wiring harness is faulty.
   Tools: Digital Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
6. [Advanced] Measure Wake-Up Circuit Voltage
   Reconnect the battery. With the BCM connected, use a multimeter to measure DC voltage on the wake-up circuit at an accessible module like the ECM. The BCM must be 'awake' (ignition on). A normal reading is approximately battery voltage (12.0V - 12.6V). A reading near 0V indicates an open circuit or a short to ground.
   Tools: Digital Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
7. [Pro Tip] Perform a Circuit Load Test
   If the short is intermittent, a load test verifies circuit integrity. With the BCM connector unplugged and battery connected, connect a 194 incandescent bulb between the wake-up circuit wire and a known good ground. The BCM supplies ~12V to this circuit when awake. If the bulb lights brightly and voltage across the bulb is at least 11V, the BCM driver is good. If it's dim or doesn't light, it indicates high resistance in the wire or a weak BCM driver.
   Tools: 194 Incandescent Bulb with test leads, Wiring Diagram, Digital Multimeter (Professional)
8. [Pro Tip] Manually Wake Up the Network
   If you suspect the BCM is faulty and not sending the wake-up signal, manually wake up the network. With all modules connected, use a test light connected to battery positive and briefly 'pulse' the wake-up circuit pin at the BCM connector. If the other modules wake up and start communicating, the BCM's wake-up driver has failed.
   Tools: 12V Test Light, Professional Scan Tool (Professional)
9. Confirm the BCM is the Cause
   If the diagnostic process rules out the wiring harness and all other connected modules, the fault lies within the Body Control Module itself. This is confirmed if the wake-up circuit is not shorted to ground, but no voltage is present on the pin when the BCM should be active.
   Tools: Digital Multimeter (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• System Voltage: 9-16V (The BCM only runs the self-test if battery voltage is within this normal operating range.)
• Vehicle Power Mode: ACC, RUN, or Remote Start Request (The fault is detected the instant the BCM requires communication and attempts to send the wake-up signal.)
• Engine RPM: 0 (Because this fault causes a no-start condition, freeze frame data is captured before the engine has a chance to run.)
• Fault Frequency Counter: 1+ (Shows how many times the fault has occurred, which tracks intermittent wiring shorts.)

Related Codes

• U0100 — 'Lost Communication With ECM/PCM'. This code is a direct symptom of U1814. The wake-up circuit failure prevents the ECM from turning on. If your scanner shows U1814 from the BCM and U0100 from other modules, the fault is on the wake-up circuit.
• U0101 — 'Lost Communication With TCM'. The TCM is on the wake-up circuit. U1814 causes the TCM to not power on, leading other modules to post U0101. If U1814 is present in the BCM, diagnose it first.
• U0131 — 'Lost Communication with Power Steering Control Module'. Frequently seen with U1814 on vehicles with electric power steering. The PSCM is on the wake-up circuit and fails to power on, triggering this code in other modules.
• U0140 — 'Lost Communication With Body Control Module'. This code suggests other modules cannot hear from the BCM. If you can't connect to the BCM at all, the BCM is dead. If you can connect to the BCM and it shows a U1814, the BCM is partially working and correctly reporting the wake-up circuit fault.

Climate & Environmental Factors

• Moisture and Humidity: High humidity and direct water intrusion accelerate corrosion in unprotected electrical connectors. On vehicles like the Chevy Equinox, the under-vehicle X411 connector is highly vulnerable.
• Road Salt: In regions that use road salt during winter, the salt acts as a catalyst for corrosion, significantly increasing the failure rate of exposed connectors and wiring, leading to shorts to ground.
• Temperature Fluctuations: Extreme temperature changes cause materials to expand and contract. This causes an intermittent short in a chafed wiring harness to make and break contact. A wire rubs against a ground when cold and stiff, but pulls away as the engine bay heats up.

How to Talk to a Mechanic About This Code

Say this: "I have a no-start condition and my scan tool shows a U1814 code in the Body Control Module, along with several other 'U' codes for loss of communication. I'd like to schedule a diagnostic appointment to trace a potential short on the powertrain wake-up circuit."

This signals to the shop that you understand the fault is a specific electrical issue, not a generic problem. It directs the technician to perform a logical circuit diagnosis rather than guessing and replacing expensive modules. Mentioning the specific circuit encourages a methodical approach.

Avoid saying:

• 'My car won't start, can you fix it?'
• 'My check engine light is on.'
• 'Just replace the BCM.'

Questions to ask before authorizing the repair:

• Did you test the wake-up circuit (GM circuit 5985) for a short to ground with a multimeter, and what was the reading?
• If you found a short in the harness, can you show me the location of the damage before you repair it?
• If you are recommending a module replacement (like the BCM or PSCM), how did you definitively rule out a wiring or connector fault?
• Does the quoted price for the module replacement include the necessary programming and calibration?
• What is the warranty on both the parts and the labor for this electrical repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: A strong choice, especially if a known TSB applies or module programming is definitely required. They have guaranteed access to the correct tools and information.
  Best for: Vehicles under warranty., Repairs covered by a specific Technical Service Bulletin (TSB), like the BCM/PSCM failure on a Chevy Trax., Complex jobs confirmed to require module replacement and proprietary software programming.
  Downsides: Highest labor rates, often 1.5-2x more than independent shops., Defaults to replacing an entire assembly (e.g., steering column) when a wiring repair is possible. (Typical cost: +50% vs. baseline)
• Independent Shop: Excellent fit, IF you find the right one. Look for a shop that advertises as an 'electrical specialist' or has deep experience with your vehicle's brand (e.g., a GM specialist).
  Best for: Out-of-warranty vehicles where cost is a major factor., Finding and repairing a short in a wiring harness, as they are often more willing to spend time on circuit-level fixes.
  Downsides: Not all shops have the expensive, manufacturer-specific tools to program a new BCM or PSCM. You must vet the shop for advanced electrical diagnostic capabilities and brand-specific experience. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. This is a complex electrical fault that is far outside the scope of a typical chain repair shop.
  Best for: Simple jobs like oil changes, tires, and batteries.
  Downsides: Technicians generally lack the specialized training for complex network diagnostics., High risk of misdiagnosis, leading to unnecessary replacement of parts like the battery or alternator for a no-start condition. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 40-50% of the car's private-party value (e.g., from Kelley Blue Book), you should seriously consider selling the car as-is or trading it in.

• Car worth $3500, fix is $2400: Walk away. The repair cost is nearly 70% of the car's value. Sell as a 'mechanic's special' or to a scrap yard.
• Car worth $22000, fix is $750: Fix it. The cost is a small fraction of the vehicle's value and addresses a critical safety and reliability issue.
• Car worth $8000, fix is $2500: Borderline. The repair is about 31% of the car's value. Before authorizing, get a second opinion to confirm if a cheaper wiring repair is possible instead of a full module replacement.

What Scan Tool You Need for This Code

Minimum: A scanner that can perform a 'Full System Scan' or 'All Module Scan' to read codes from the Body Control Module (BCM), not just the engine computer (ECM).

A basic $20 code reader only checks for engine and emissions codes. It cannot communicate with the BCM, which is the module that sets the U1814 code. You will be completely blind to the actual fault.

Budget: TOPDON TopScan / MUCAR BT200 (~$70) — These Bluetooth dongles pair with your smartphone and perform a full system scan, allowing you to see the U1814 code in the BCM and the related U-codes in other modules. Some offer limited bidirectional tests.

Mid-range: Innova 5610 / Launch CRP919XBT (~$350) — Provides full system diagnostics and adds crucial bidirectional controls. This allows you to command components and run active tests to help isolate the fault between the BCM, wiring, or another module.

Professional: Autel MaxiCOM MK906BT / Launch X431 Series (~$500-1200) — Offers full OEM-level diagnostics, advanced bidirectional control, and the ability to perform module programming. If the BCM or PSCM needs to be replaced, a tool at this level is required to program the new part to the vehicle.

How to Clear the Code After You Fix It

1. After repairing the short or replacing the faulty module, use a professional OBD-II scan tool to clear all DTCs from all modules.
2. For GM vehicles, complete a specific drive cycle to reset all readiness monitors for emissions testing.
3. In cases involving GM TSB 20-NA-206, codes are 'unrecoverable' and will not clear until both the BCM and PSCM are replaced and programmed.

Drive cycle (~30 minutes): A general GM drive cycle includes: a cold start (engine temp below 122°F/50°C), 2-3 minutes of idling with A/C on, accelerating to 55 mph and holding for 3 minutes, coasting down to 20 mph, accelerating to 60 mph and holding for 5 minutes, then coasting down again.

Readiness monitors affected: Comprehensive Component Monitor, Misfire Monitor, Fuel System Monitor, Catalyst Monitor, EVAP System Monitor, Oxygen Sensor Monitor

Before emissions retest: drive at least 100 miles to fully set monitors.

Watch out for:

• Disconnecting the battery does not clear the codes from all modules and resets all readiness monitors to 'Not Ready'.
• The code immediately returns if the underlying short circuit is not properly repaired.
• Attempting to clear 'unrecoverable' codes in a PSCM damaged by a bad BCM fails until the hardware is replaced.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: A U1814 code with an illuminated Check Engine Light is an automatic failure. The inability to communicate with the ECM to check readiness monitors also results in a test failure.
• New York: The NYS DMV inspection includes an OBD-II scan. Any communication DTC that turns on the Malfunction Indicator Lamp (MIL) causes the vehicle to fail the test.
• Texas: In the 17 counties requiring emissions testing, a vehicle with code U1814 and an active Check Engine Light fails the OBD portion of the inspection.

Most Commonly Affected Vehicles

• Chevrolet Silverado 1500 (2019-2022) — Subject to GM TSB 18-NA-114 for engine harness chafing against the G100 ground stud, causing a short on circuit 5985.
• GMC Sierra 1500 (2019-2022) — Shares the same platform and wiring harness chafing issues as the Chevrolet Silverado, as noted in TSB 18-NA-114.
• Chevrolet Equinox (2010-2017) — Prone to corrosion in the X411 connector under the rear of the vehicle, which shorts communication lines and causes U1814, as noted in GM TSB #PIT5427B.
• Chevrolet Trax (2017-2022) — A prime example of the cascading failure described in TSB 20-NA-206, where an internal BCM fault induces failure in the PSCM, requiring replacement of both the BCM and steering column.
• Cadillac CTS (2008-2014) — A known issue documented in GM TSB #PIC4740F points to unseated pins and harness chafing at the transmission's main electrical connector (X1), causing communication codes.
• Saab 9-5 (2010-2011) — Built on a GM platform (Epsilon II), these vehicles exhibit the same U1814 failure mode where the BCM detects a short on the wake-up circuit and fails to activate the ECM.
• Chevrolet Cruze (2011-2015) — Known for communication issues with the TCM, often traced back to poor connections or bent terminals in the underhood fuse block connectors, which affect wake-up signals.
• Ford Various Models (2015-2023) — While Ford uses different nomenclature, they experience similar network communication faults and wake-up issues traced to wiring harness problems near the driver's side seat base or damaged Gateway Modules (SGW).

Manufacturer-Specific Notes

• General Motors (Chevrolet, GMC, Cadillac, Saab): This code is most prevalent on GM vehicles. GM TSB 20-NA-206 warns that an internal BCM failure causing U1814 induces a failure in the Power Steering Control Module (PSCM), requiring replacement of both the BCM and the entire steering column assembly.
• General Motors: Once a communication fault like U0100 is set in a module like the PSCM due to the U1814 condition, it becomes 'unrecoverable'. The code cannot be cleared until specific drive cycle and shutdown procedures are completed. The scan tool reports the clear command was 'Rejected by control module'.
• General Motors: There are no active recalls for code U1814. However, GM has issued multiple Technical Service Bulletins (TSBs) like 18-NA-114 and 20-NA-206 that address common causes. Repairs are covered if the vehicle is still within its original warranty period.
• Chevrolet: A specific variation, 'U1814 5A', has a completely different meaning: 'Fuel Level Sensor Circuit High Voltage'. This is unrelated to the communication fault and points to an issue with the fuel sending unit or its wiring.
• Saab: For the 2010-2011 9-5, which uses a GM electrical architecture, U1814 is logged with suffixes like '01' (Short to Battery), '02' (Short to Ground), or '04' (Open Circuit), providing specific diagnostic direction directly from the code itself.

Real Owner Stories

2019 GMC Sierra 1500 with 55K miles

Vehicle was a no-crank, no-start in the driveway. Multiple warning lights including 'Service Power Steering' were on. Scan tool showed U1814 in the BCM and U0100/U0131 in other modules.

What they tried:

1. Owner initially suspected a dead battery, but jumping it had no effect.
2. Towed to a dealer who identified the common wiring harness chafing issue outlined in GM TSB 18-NA-114.

Outcome: Technician located the engine harness rubbing against a sharp edge on the ECM/TCM bracket. The damaged wires on circuit 5985 were repaired, and the harness was protected with an anti-abrasion sleeve and secured with zip ties. Total cost was $450 for 3 hours of diagnostic and repair labor.

Lesson: For late-model GM trucks, a sudden no-start with multiple communication codes is very likely a wiring harness chafing issue. Mentioning the TSB to your mechanic speeds up diagnosis.

2017 Chevy Equinox with 80K miles

Car intermittently failed to start. When it failed, the scan tool only communicated with the BCM, which had a U1814-02 code (short to ground). After sitting for a while, it sometimes started and ran normally.

What they tried:

1. An independent shop suspected a short in the wiring and spent hours trying to trace it without success.
2. The shop recommended replacing the ECM, assuming it was shorted internally. This did not fix the problem.

Outcome: The owner took it to a specialist. The tech tested the wake-up circuit and found no hard short to ground. Suspecting a faulty BCM, he used a test light to manually pulse 12V onto the wake-up circuit, which successfully woke up the other modules. This proved the BCM's driver had failed. Replacing and programming the BCM fixed the issue. The owner paid for a misdiagnosis and an unnecessary ECM.

Lesson: U1814 doesn't always mean there's a short in the wiring. The BCM itself fails and falsely reports a short. If a short can't be found, the BCM becomes the primary suspect.

2020 Chevy Trax with 40K miles

While driving, the power steering suddenly failed and a 'Service Power Steering' message appeared, followed by a no-start condition after being shut off. The dealer found U1814 in the BCM and an 'unrecoverable' U0100 code in the Power Steering Control Module (PSCM).

What they tried:

1. The technician initially tried to clear the codes, but the U0100 in the PSCM was 'Rejected by control module'.
2. Following GM TSB 20-NA-206, they diagnosed a cascading failure caused by the BCM.

Outcome: An internal failure in the BCM sent a voltage spike that destroyed the PSCM. Per the TSB, both the BCM and the entire steering column assembly (which contains the PSCM) had to be replaced and programmed. The repair cost over $2,200.

Lesson: On certain GM models, a faulty BCM causes expensive collateral damage. A 'Service Power Steering' message accompanying a U1814 code is a major red flag for this specific, costly failure scenario.

How to Prevent This Code From Triggering

• Periodically inspect wiring harnesses in the engine bay. (Every oil change) — Look for harnesses resting on sharp metal edges, engine brackets, or studs. Early detection of rubbing allows you to secure the harness before the insulation wears through.
• Apply dielectric grease to the seals of major electrical connectors. (When connectors are disconnected for service) — Dielectric grease is a non-conductive sealant that protects the connector's rubber seals from drying out and blocks moisture and road salt from entering, preventing the corrosion that leads to shorts.
• Install protective wire coverings in vulnerable areas. (As a one-time upgrade) — Adding anti-abrasion tape, split-loom tubing, or specialized sleeves provides a sacrificial layer that protects the harness from vibration and chafing.
• Ensure all harness clips and retainers are intact after any repair. (After any professional or DIY repair) — A single forgotten or broken clip allows a harness to sag or vibrate against a component, leading to a chafing failure months later. These clips are critical for proper routing.
• Regularly wash the vehicle's undercarriage. (Monthly, especially in winter (salt-belt regions)) — Washing away road salt and grime reduces the risk of it penetrating unprotected connectors and causing catalytic corrosion, which creates unintended electrical paths to ground.

Frequently Asked Questions

Can I fix a U1814 code myself?

Fixing a U1814 code is an advanced repair. While a visual inspection of the wiring is possible for a DIYer, properly diagnosing the short with a multimeter, performing load tests, and accessing modules requires professional skill and vehicle-specific diagrams. Replacing modules almost always requires expensive, manufacturer-specific programming tools.

Why did my car not start but then start up later?

The short in the wiring is likely intermittent. A vibration, temperature change, or moisture level change temporarily moves a chafed wire away from the metal it touches, allowing the modules to wake up and the car to start. The problem will almost certainly return and worsen over time.

Could a bad battery cause a U1814 code?

While a weak battery causes a multitude of electrical problems, it is not a direct cause of U1814. This code specifically indicates a short-to-ground condition detected by the BCM. However, a healthy battery is crucial for accurate diagnosis, as system voltage must be between 9-16V for the diagnostic to run.

My mechanic replaced a module but the problem returned. What now?

This happens when the root cause is misdiagnosed, often overlooking an underlying wiring harness issue. Alternatively, a faulty BCM can damage other modules like the PSCM. If only the secondary damaged module is replaced, the new part will be destroyed again.

What is a 'gateway module' and could it cause this?

A gateway module (GWM) acts as a network router for your car, directing communication between different CAN bus networks. While a faulty gateway causes widespread communication loss, the U1814 fault is more specific. It points directly to the 'wake-up' command from the BCM rather than general network traffic.

How much does it cost to diagnose a U1814 code?

Most shops charge a diagnostic fee for complex electrical issues, typically ranging from $150 to $300. This fee covers the technician's time using specialized tools to trace the short circuit. Tracing the physical short is often the most time-consuming part of the repair.

What does the subtype U1814-02 mean?

The '-02' is a failure subtype identifier used by manufacturers like GM to provide specific diagnostic direction. U1814-02 specifically indicates 'Powertrain Wake Up Communication Circuit Short to Ground'. This confirms the exact nature of the fault the BCM has detected.

My mechanic says the BCM needs programming. What is that?

A new BCM is a blank slate that must be programmed with software specific to your car's Vehicle Identification Number (VIN). This programming configures it for your vehicle's specific options and allows it to communicate with other modules. Without programming, the car will not start.

Key Takeaways

• Code U1814 indicates the Body Control Module (BCM) detected a short-to-ground on the 12V wake-up circuit, preventing the engine and transmission computers from turning on.
• This fault immediately causes a no-start condition or a sudden loss of power steering while driving, requiring an immediate tow.
• Over 60% of U1814 codes stem from a chafed wiring harness shorting against the engine block or chassis, rather than a failed computer module.
• Never replace the BCM without testing the wake-up circuit with a multimeter first; a faulty BCM can send voltage spikes that destroy the $1,200+ Power Steering Control Module (PSCM).