OBD-II Code U0268: Lost Communication With Glow Plug Control Module 'B' or Driver-Assist Module

What Does U0268 Mean?

U0268 is a communication network code with two distinct meanings. For diesel engines, the Powertrain Control Module (PCM) lost communication with the Glow Plug Control Module 'B' (GPCM), which heats cylinders for cold starts. For modern gasoline vehicles, it indicates lost communication with a driver-assist module, such as a side blind-spot radar sensor or parking camera.

Technical definition: The SAE definition is "Lost Communication With Glow Plug Control Module B". However, manufacturers frequently assign this code to "Lost Communication With Side Object Detection Control Module B" or a side camera assembly. This means the specific module stopped responding on the vehicle's Controller Area Network (CAN bus).

Can I Drive With U0268?

Yes, But With Caution. For diesel engines, yes, but you risk being stranded. The engine becomes progressively harder to start in cold weather and eventually fails to start. For gasoline vehicles, the car is mechanically safe to drive, but critical safety features like blind-spot monitoring are disabled, increasing collision risk by up to 23%.

Common Causes

• Failed Module (GPCM or Side Object Sensor) (Very Common) — The module itself is the most frequent failure point. ADAS modules in bumpers fail from water intrusion and internal short circuits. GPCMs fail from years of engine heat cycles and vibration.
• Damaged Wiring Harness or Corroded Connector (Very Common) — Wires running to the module corrode, chafe, or break. Bumper harnesses rub against sharp metal edges, and connector pins suffer from green corrosion, breaking the electrical connection. Rodents also chew these wires.
• Blown Fuse (Common) — A blown fuse cuts power to the module, stopping communication. This almost always indicates an underlying short circuit in the wiring harness that requires repair.
• Broken Module Mounting Bracket (Less Common) — A minor bumper impact breaks the plastic radar mounting bracket, misaligning the sensor. The module disables itself and stops communicating to prevent false safety warnings.
• Weak Vehicle Battery (Less Common) — Low system voltage during startup causes modules to fail their initial self-test. If U0268 appears alongside other electrical codes, load-test the battery.
• Faulty PCM or Gateway Module (Rare) — The main computer that sends and receives signals fails. This causes multiple 'U' codes for various systems simultaneously, not just U0268.

Symptoms

• 'Service Driver Assist' or 'Blind Zone Alert' message (Gasoline) — The primary symptom for non-diesels. Blind-spot monitoring, lane change alert, and rear cross-traffic alert are completely disabled.
• Engine is hard to start or will not start when cold (Diesel) — Without glow plugs heating the cylinders, diesel fuel fails to ignite properly, causing extended cranking or a complete no-start.
• Check Engine Light is on — The controlling module illuminates the check engine light immediately after detecting the communication loss.
• Excessive white smoke and rough idle on startup (Diesel) — Unburnt diesel fuel pushes into the exhaust during a difficult start, creating white smoke and a rough idle until the engine warms up.

Diagnostic Flowchart

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

Common Fixes & Costs

• Replace and Calibrate Side Object/Camera Module — Parts: $250-$600, Labor: $300-$800, ~2.5 hr book time (Professional)
  : OEM
  : OEM
• Replace Glow Plug Control Module 'B' — Parts: $150-$350, Labor: $100-$200, ~1.2 hr book time (Intermediate)
  : OEM
  : OEM
• Repair Damaged Wiring Harness and Connector — Parts: $30-$100, Labor: $250-$850, ~3.5 hr book time (Professional)
• Replace Blown Fuse and Repair Short — Parts: $5-$15, Labor: $100-$250, ~1.0 hr book time (Intermediate)

DIY vs Professional

• Replace Side Object/Camera Module — Beginner:
  Tools: Trim removal tools, socket set, manufacturer-specific diagnostic software, ADAS calibration target system.
• Replace Glow Plug Control Module — Beginner:
  Tools: Basic hand tools. Professional scan tool required for programming on newer models.
• Repair Damaged Wiring Harness — Beginner:
  Tools: Multimeter, wiring diagrams, wire strippers, crimping tool, heat shrink tubing.

Used vs. New Parts: Buying Guide

When a used part is worth it: For a GPCM on an older diesel truck where the part is plug-and-play, a used module is cost-effective. For ADAS modules, used parts are highly discouraged due to high failure rates from water intrusion and programming complexities.

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

Donor quality checklist:

• Avoid ADAS modules from the 'salt belt' due to corrosion risk.
• Verify the exact part number matches.
• Ensure the salvage yard offers a 30-90 day warranty.

Decision logic:

• If The part is an ADAS module requiring programming. → Buy new. Shops cannot or will not program used ADAS modules due to liability.
• If The part is a GPCM for a vehicle over 10 years old. → A tested, used part is a reasonable risk.
• If The cost of labor for the repair is high. → Buy new to avoid paying for labor twice if the used part fails.

Warranty tradeoff: Used parts have a 30-90 day warranty. New aftermarket parts carry a 1-year to lifetime warranty. New OEM parts have a 1-year warranty.

Worst-case if a used part fails: $400-$1000

What Happens If You Wait — Timeline

1. 0-4 weeks: For ADAS: Blind spot monitoring is disabled. For Diesel: Engine requires an extra second of cranking below 50°F. (MPG impact: 0%% · Added cost: $0)
2. 1-3 months: For ADAS: System remains disabled. For Diesel: Hard starting is frequent below 40°F, with white smoke from exhaust. Starter and battery strain increases. (MPG impact: 1-3% (Diesel)% · Added cost: $50)
3. 3-6 months: For ADAS: A preventable lane-change incident occurs. For Diesel: Vehicle will not start below freezing. Repeated cranking damages the starter or battery. (MPG impact: 0%% · Added cost: $500+)
4. 6+ months: For ADAS: Corroded module causes a parasitic draw, killing the battery. For Diesel: Extreme cranking causes 'cylinder wash,' accelerating engine wear. (MPG impact: N/A% · Added cost: $1000+)

Cost of Not Fixing It

• Immediate: Loss of blind-spot monitoring (Gasoline) or hard starting in cold weather (Diesel). (Added cost: 0)
• 1-3 months (Diesel): Progressively harder starting strains the battery and starter motor, leading to premature failure. (Added cost: $250-$1200)
• 3+ months (Diesel): Eventual no-start condition. Repeated cranking with unburnt fuel causes cylinder wash, accelerating engine wear. (Added cost: $500+)
• Ongoing (Gasoline): Continued increased risk of lane-change and backup accidents. (Added cost: $500+)

Diagnosis Steps

1. Scan for All Trouble Codes
   Use a bidirectional scanner to read codes from all modules. Document codes like U0106 or U0269, which point to a specific side or shared power issue.
   Tools: Professional OBD-II Scanner (Beginner)
2. Inspect Fuses
   Locate the module's fuse and test it for continuity. A blown fuse confirms a short circuit exists.
   Tools: Owner's Manual, Multimeter (Beginner)
3. Visually Inspect Wiring and Connector
   Access the module (often requiring bumper removal for ADAS). Unplug the connector and check for green corrosion, melted plastic, or chafed wires rubbing on the frame.
   Tools: Flashlight, Trim Removal Tools, Socket Set (Intermediate)
4. Test Power and Ground
   With the ignition on, verify the module receives 12V+ on the power pin and has near 0 ohms resistance to chassis ground. A missing power or ground mimics a dead module.
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Intermediate)
5. Test CAN Bus Resistance
   With the battery disconnected, measure resistance between CAN High and CAN Low at the connector. A healthy bus reads 60 ohms. 120 ohms indicates an open circuit; 0 ohms indicates a short.
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
6. Test CAN Bus Voltage
   With the ignition on, measure the DC voltage of each CAN line to ground. CAN High averages 2.6V to 3.5V; CAN Low averages 1.5V to 2.4V. Deviations indicate a short to power or ground.
   Tools: Multimeter, Vehicle-Specific Wiring Diagram (Advanced)
7. Monitor Live Data
   Access the gateway module's live data. Check if the missing module reports as 'Present' or 'Offline' to confirm network status.
   Tools: Professional OBD-II Scanner (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Module Power Status: Offline or Not Present (The gateway module polls the network and receives no response from the GPCM or ADAS module.)
• Vehicle Speed: 0 mph (at startup) or Any Speed (during operation) (The communication check fails during the initial key-on self-test, or is lost while driving.)
• Battery Voltage: 11.8V - 14.5V (Typically set when system voltage is normal; however, a low voltage event during startup triggers temporary communication codes.)
• Ignition Status: Run or Start (Logged when the ignition is on and the master control module expects to see the subordinate module on the network.)

Related Codes

• U0106 / U0269 — Direct counterparts for the opposite side module. Seeing both codes simultaneously strongly suggests a shared power, ground, or wiring harness issue.
• P0670 / P0683 — Indicates the PCM can communicate with the GPCM, but the GPCM reports an internal error. These often precede a total failure that results in U0268.
• P0671 - P0678 — Circuit faults for individual glow plugs. If you have a U0268, ignore these codes until communication is restored, as the reporting module is offline.
• U0075 — A general 'Control Module Communication Bus Off' code. Often set alongside U0268 on GM vehicles, confirming a network communication failure.

Climate & Environmental Factors

• Cold Weather: Significantly impacts diesel engines. A marginal glow plug system fails in cold temperatures, leading to a hard-start or no-start condition.
• High Humidity and Road Salt: The primary cause of ADAS module failure. Salt spray infiltrates the rear bumper module's seals, causing severe corrosion of the connector pins and internal circuit board.

How to Talk to a Mechanic About This Code

Say this: "I have a U0268 code on my [Year, Make, Model]. I believe it relates to the [Side Blind Spot Module / Glow Plug Control Module]. I'd like to schedule a diagnostic appointment to confirm if the fault is the module itself, the wiring, or a fuse before authorizing parts replacement."

This focuses the technician on the correct system and frames the job as a diagnostic task, preventing them from immediately quoting an unnecessary module replacement.

Avoid saying:

• 'Just fix whatever's wrong'
• 'My check engine light is on, can you look at it?'
• 'My blind spot thingy is broken'

Questions to ask before authorizing the repair:

• For ADAS: Did you find corrosion on the module or connector? Will the connector pigtail be replaced as well?
• For ADAS: Does your quote include the cost of the mandatory ADAS calibration?
• For Diesel: Did you confirm the module is receiving proper power and ground before condemning it?
• For Diesel: Does the new part require programming on my specific vehicle?
• What is the warranty on the parts and labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended. The dealer ensures required programming and calibration are done correctly.
  Best for: Vehicles under warranty, ADAS-related U0268, as they have required calibration equipment, Newer diesel trucks where the GPCM requires proprietary software
  Downsides: Highest labor rates, More likely to replace an entire harness than perform a wiring repair (Typical cost: +50% vs. baseline)
• Independent Shop: Conditionally Recommended. Excellent if the shop is ASE-certified and specifically equipped for ADAS calibration.
  Best for: Out-of-warranty vehicles, Diesel GPCM replacement on older trucks, Diagnosing and repairing wiring issues
  Downsides: Quality varies. Must be vetted for ADAS capability., May lack proprietary programming software. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID. This code requires advanced diagnostic capabilities beyond typical chain shops.
  Best for: Simple maintenance like oil changes and brakes
  Downsides: Technician skill varies dramatically, Lacks specialized tools for CAN bus diagnostics or ADAS calibration (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, consider selling or trading it in. For older, high-mileage vehicles, this threshold is 30-40%.

• Car worth $10000, fix is $1500: Fix it. The repair cost is 15% of the vehicle's value, restoring a critical safety feature or ensuring the vehicle starts.
• Car worth $4000, fix is $1800: Borderline. The repair is 45% of the car's value. Get a second opinion and assess the car's overall health.
• Car worth $2500, fix is $1500: Walk away. The repair cost is 60% of the vehicle's value. It is not financially sound.

What Scan Tool You Need for This Code

Minimum: A tool that reads manufacturer-specific codes from all modules, not just generic engine codes.

A basic reader only confirms the code exists. It cannot identify the offline module, check network codes, or access live data.

Budget: BlueDriver Pro (~$99) — Reads enhanced codes from systems like the Active Safety Module. Views live data, but cannot program new modules.

Mid-range: XTOOL D7 or Foxwell NT809 (~$350-450) — Full-system, bidirectional scan tools. Commands modules directly and tests the CAN bus network.

Professional: Autel MaxiCOM MK906BT or Launch X431 Series (~$600-1300) — Provides OEM-level diagnostics and performs programming and calibration required after replacing an ADAS or GPCM module.

Rent vs buy: Rent to confirm the code, but buy to diagnose. Proper diagnosis requires a mid-range or professional tool.

How to Clear the Code After You Fix It

1. Reconnect the battery if it was disconnected.
2. Use a professional-grade OBD-II scan tool to clear DTCs from all modules.
3. For ADAS module replacement, perform the manufacturer-required programming and calibration procedure.
4. Perform a complete drive cycle to allow readiness monitors to run.

Drive cycle (~20 minutes): 1. Cold start (engine temp below 122°F). 2. Idle for 2-3 minutes with electrical loads on. 3. Accelerate to 55 mph for 3-5 minutes. 4. Coast down to 20 mph without braking. 5. Accelerate to 55-60 mph and hold for 5 minutes.

Readiness monitors affected: Comprehensive Component Monitor, Misfire Monitor

Before emissions retest: drive at least 50 miles to fully set monitors.

Watch out for:

• Disconnecting the battery does not clear the code permanently and resets all readiness monitors to 'Not Ready'.
• If the root cause is not fixed, the code returns immediately.
• Failing to program a new ADAS or GPCM module prevents the code from clearing.

Will This Fail Emissions / State Inspection?

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

• California: An illuminated Check Engine Light results in an automatic failure. A full drive cycle must be completed after repair.
• New York: A Check Engine Light on for U0268 is an automatic failure. The vehicle must be driven to get systems 'ready' for re-inspection.
• Texas: An active U0268 code causes an automatic failure in emissions-testing counties. Diesel vehicles are exempt.

Most Commonly Affected Vehicles

• Ford F-Series Super Duty (with Powerstroke V8) (2003-2016) — The GPCM is a common failure item, and wiring is frequently damaged by heat or rodents.
• Cadillac ATS, CTS, XTS, XT5, Escalade, CT6 (2013-2020) — A very common code referring to a failed Side Blind Zone Alert module due to water intrusion in the rear bumper.
• Chevrolet / GMC Silverado / Sierra, Tahoe / Yukon, Traverse (2004-2020) — On modern SUVs, it is almost always a failed side object detection module or a shorted front bumper harness per TSB PIT5487F.
• Buick Envision, Enclave (2016-2021) — Indicates lost communication with an active safety system module. TSB PIT5441C notes a faulty technician scan tool triggers the code by mistake.
• Dodge Ram 2500/3500 (with Cummins) (2007-2018) — These engines use an intake air grid heater. The control module for this system fails, leading to communication loss.
• Volkswagen Jetta / Golf / Passat (with TDI) (2005-2015) — The glow plug harness and control module are common failure points.
• Mercedes-Benz Sprinter / E-Class / GL-Class (with BlueTec) (2010-2016) — The glow plug controller module is a frequent failure item and is often replaced as a set with the glow plugs.
• Toyota Land Cruiser, 4Runner (with Multi-Terrain Monitor) (2016-2021) — U0268 means 'Lost Communication with side television camera assembly RH'. The issue is typically the passenger-side camera or its wiring.

Manufacturer-Specific Notes

• General Motors: TSB #PIT5487F identifies a common wiring harness chafe point on the front passenger-side bumper bar of 2015-2020 SUVs that shorts out and causes this code. TSB #PIT5441C warns that a faulty diagnostic interface cable can induce a false U0268 code.
• Ford: On Powerstroke V8 engines, GPCM 'A' (U0106) controls the passenger side cylinders and GPCM 'B' (U0268) controls the driver's side cylinders.
• Toyota: On models with advanced camera systems, U0268 specifically means 'Lost Communication with side television camera assembly RH'. The fault is with the passenger-side camera.
• Cadillac (GM): On 2017-2018 XT5s, GM bulletin PIT5782C states that if one side object detection module is replaced, programming fails. Both left and right modules must be replaced simultaneously.

Real Owner Stories

2014 Cadillac XTS with "Service Driver Assist" message

The 'Service Driver Assist' warning appeared, and blind-spot monitoring stopped working. Code U0268 was present.

What they tried:

1. Initial diagnosis pointed to the passenger side object detection module.

Outcome: Owner removed the rear bumper cover and found severe green corrosion on the module and connector. Replacing both resolved the issue.

Lesson: For ADAS codes on GM vehicles, the cause is almost always water intrusion. Always inspect the connector; replacing only the module leads to repeat failure.

2015 Cadillac Escalade with multiple driver assist warnings

Adaptive cruise control became inoperative. Codes U0265, U0268, and U0269 were present.

What they tried:

1. Dealer replaced the 12-volt battery.
2. Dealer replaced the main driver assist control module.
3. Identified a short in the front wiring harness.

Outcome: The cause was a chafed wiring harness in the front bumper shorting against the metal bumper bar (GM TSB #PIT5487F). Repairing the harness fixed it.

Lesson: When multiple ADAS codes appear, suspect a shared wiring harness or power issue rather than multiple failed modules.

2006 GMC Sierra 2500HD (Duramax) with a no-start in cold weather

Vehicle cranked but would not start cold. The 'wait to start' light did not illuminate. Code U0106 (counterpart to U0268) was present.

What they tried:

1. Tested glow plugs (functional).
2. Checked GPCM fuses (good).

Outcome: Tested for power at the GPCM and found it had power and ground but sent no signal. Replacing the GPCM resolved the no-start.

Lesson: On a diesel with a no-start, if fuses are good, the module itself is the likely failure point.

2018 Buick Envision with false U0268 code

During unrelated diagnosis, the scan tool reported code U0268 and a 'Service Active Safety' message.

What they tried:

1. Technician suspected diagnostic equipment.

Outcome: Following GM TSB #PIT5441C, the technician used a different MDI interface cable. The code did not return.

Lesson: If U0268 appears unexpectedly at a shop, faulty scan tool cables induce false codes. Rule this out before authorizing repairs.

How to Prevent This Code From Triggering

• Apply dielectric grease to ADAS module connectors (Anytime the bumper is removed.) — Seals electrical connectors from moisture, preventing water intrusion and corrosion.
• Clean rear bumper and sensor areas regularly (Monthly, especially in winter.) — Prevents buildup of dirt and salt that holds moisture against the module's seals.
• Inspect and secure wiring harnesses (During under-vehicle maintenance.) — Ensures harnesses are not rubbing against sharp metal edges, preventing future short circuits.
• Maintain a healthy battery and clean terminals (Annually.) — Ensures stable voltage during startup, preventing random communication codes.
• Replace diesel glow plugs as a set (Every 60,000-100,000 miles.) — Failing glow plugs draw incorrect current, stressing the GPCM. Replacing them extends module life.

Frequently Asked Questions

My car isn't a diesel, why did I get a U0268 code?

On modern gasoline vehicles, especially from General Motors, U0268 refers to a communication failure with a driver-assist module. This is typically a blind-spot radar sensor in the rear bumper. You will usually see a 'Service Driver Assist' message.

My mechanic says their scan tool might be the problem. Is that possible?

Yes. GM issued TSB #PIT5441C warning that a faulty diagnostic interface cable can interfere with the network and generate false U0268 codes. A technician should try a different cable before recommending repairs.

The mechanic wants to replace both blind spot modules. Is this necessary?

In specific cases, yes. For certain 2020-2021 GM models, a service bulletin states that replacing only one module causes the programming sequence to fail. Both modules must be replaced simultaneously for successful calibration.

What is the difference between a wiring short and a bad module?

A wiring short often blows a fuse and causes sudden failure, frequently due to harness chafing. A bad module usually fails from internal water corrosion and may act intermittently before dying completely. Testing the connector for 12V power and ground isolates the true cause.

Can I just ignore code U0268?

For a diesel, ignoring it eventually leaves you stranded as the engine fails to start in cold weather. For a gasoline car, you lose critical safety features like blind-spot monitoring. Driving without these systems significantly increases your risk of a collision.

How much does it cost to fix U0268?

Replacing a diesel Glow Plug Control Module costs $250 to $550. Replacing a gasoline driver-assist radar module costs $550 to $1,400 due to bumper removal and mandatory ADAS calibration. Wiring repairs vary widely from $280 to $950 based on diagnostic time.

Key Takeaways

• U0268 indicates a failed driver-assist sensor (like a blind-spot radar) on gasoline cars, or a failed Glow Plug Control Module on diesel engines.
• For ADAS systems, water intrusion in the rear bumper is the leading cause, requiring a $550 to $1,400 module replacement and professional calibration.
• For diesel engines, a failed GPCM causes hard starting below 50°F and typically costs $250 to $550 to replace.
• Before replacing any modules, use a multimeter to verify the module receives 12V power and has a solid ground, as a $10 blown fuse mimics a dead module.
• Do not attempt to DIY an ADAS module replacement; the new sensor requires manufacturer-specific software and target boards to calibrate the radar safely.