Ultimate Guide to OBD-II Code U1124: Lost Communication With Power Steering Control Module

What Does U1124 Mean?

Code U1124 indicates the vehicle's main computer lost connection with the Power Steering Control Module (PSCM). All electronic modules communicate over the Controller Area Network (CAN) bus. When this code stores, the PSCM is offline—it is not sending or receiving signals, which instantly deactivates the electric power steering (EPS) system.

Technical definition: Lost Communication With Power Steering Control Module (PSCM). This Diagnostic Trouble Code (DTC) sets when the PSCM fails to transmit or receive messages on the Controller Area Network (CAN) bus for a specified period.

Can I Drive With U1124?

No — Do Not Drive. The power steering fails without warning, making the vehicle extremely difficult to steer at low speeds. This sudden increase in steering effort causes a loss of control in parking lots, during turns, or in emergency maneuvers. Driving more than a few miles to a repair shop is strongly discouraged.

Common Causes

• Low or Unstable Battery Voltage / Faulty Alternator (Very Common) — EPS systems require massive, stable voltage. 🎬 Watch: How a weak battery triggers communication trouble codes. A weak battery, failing alternator, or corroded terminals cause voltage drops that instantly knock the PSCM offline.
• Damaged Wiring, Connectors, or Grounds (Very Common) — Harsh under-vehicle conditions expose the PSCM wiring harness to moisture, road salt, and vibrations. This causes corrosion, frayed wires, loose pins, or rusted chassis grounds that sever CAN bus communication.
• Blown EPS Fuse or Faulty Relay (Common) — High-amperage fuses and relays protect the PSCM. A blown fuse cuts all power to the module, forcing it offline and triggering a U1124 code from other modules searching for it.
• Faulty Power Steering Control Module (PSCM) (Common) — Internal electronic component breakdown, heat stress, or age destroys the module. Replace the PSCM only after ruling out power, ground, and wiring faults.
• Software Glitches or Corrupted Data (Common) — Voltage spikes from jump-starts or battery replacements corrupt module software. A dealership software re-flash or CAN gateway re-coding often resolves this.
• Faulty Intelligent Battery Sensor (IBS) (Less Common) — On BMWs and modern Jeeps, a failing Intelligent Battery Sensor (IBS) creates erratic electrical behavior and voltage fluctuations, leading to a cascade of communication codes including U1124.
• CAN Bus Network Failure or Aftermarket Interference (Rare) — Improperly installed aftermarket alarms or a short circuit in the main CAN wiring disrupts network communication. This is typically accompanied by a flood of other 'U' codes from various modules.

Symptoms

• Heavy or No Power Steering Assist — Steering becomes extremely difficult to turn, especially at low speeds or when parking, because the electric assist motor shuts down.
• Intermittent Power Steering Function — Power steering works correctly one moment and fails the next, pointing directly to a loose connection or voltage supply issue.
• Power Steering Warning Light On (also visible on scanner) — The dashboard illuminates a power steering warning light, typically a steering wheel icon with an exclamation mark.
• Check Engine Light On (also visible on scanner) — The Powertrain Control Module (PCM) illuminates the Check Engine Light because it considers power steering status critical safety data.
• Multiple Warning Lights (also visible on scanner) — ABS, traction control, or other warning lights appear alongside the power steering light during a wider network or voltage failure.

Diagnostic Flowchart

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

Common Fixes & Costs

• Charging or Replacing the Vehicle Battery — Parts: $150-$400, Labor: $0-$100, ~0.5 hr book time (DIY)
• Replacing a Blown Fuse — Parts: $1-$10, Labor: $0, ~0.1 hr book time (DIY)
• Repairing Damaged Wiring or Cleaning Ground Connections — Parts: $10-$50, Labor: $100-$300, ~1.5 hr book time (Intermediate)
• Dealership Software Update/Reprogramming — Parts: $0, Labor: $150-$350, ~1 hr book time (Professional)
• Replacing the Power Steering Control Module (PSCM) or Rack Assembly — Parts: $400-$1500, Labor: $250-$600, ~2.5 hr book time (Professional)
  Ford F-150 (2011-2014): OEM AL3Z-3504-CRM (Remanufactured Rack Assembly) (Alt: Dorman 601-900 (New Rack with Programmer), Cardone 22-2121 (Remanufactured Rack). Dorman unit includes a programmer, avoiding a dealer visit.)
  Jeep Grand Cherokee (2014-2015): OEM 1NJ74LU5AC (PSCM Module) (Alt: Aftermarket options require replacing the entire rack assembly. Verify part by VIN.)
  Chevrolet Silverado (2007-2013): OEM 25962338 (PSCM Module) (Alt: ACDelco Gold (Professional) or Silver (Advantage). Part requires programming.)

Used vs. New Parts: Buying Guide

When a used part is worth it: A used or remanufactured EPS rack makes sense for older, high-mileage vehicles where a new OEM part is cost-prohibitive.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the part number exactly, as similar racks have different internal programming.
• Source from a reputable salvage yard offering at least a 90-day warranty.
• Inspect electrical connectors for corrosion and boots for tears indicating contamination.

Decision logic:

• If The vehicle is under warranty or part of a recall/extended coverage program. → Use a new OEM part installed by a dealer at no cost.
• If The failure requires module programming that is difficult or impossible for used parts. → Buy a new part (OEM or quality aftermarket) guaranteed to be programmable.
• If The vehicle is over 150,000 miles and budget is the primary concern. → A used or remanufactured part is a viable option, but has a shorter lifespan.

Warranty tradeoff: Used parts include a 30-90 day warranty on the part only. New aftermarket parts offer 1-year to limited lifetime warranties. New OEM parts offer 1-2 year warranties. Labor is never covered on a failed used part.

Worst-case if a used part fails: $500-$1000 if a used rack fails prematurely, requiring a second labor and alignment charge.

What Happens If You Wait — Timeline

1. 0-1 week: Intermittent loss of power steering, often resets after restarting the car. Power steering warning light flickers. Code U1124 is logged. (MPG impact: 0%% · Added cost: $0)
2. 1 week - 2 months: Power steering loss becomes frequent and is not restored by restarting. Steering is consistently heavy, creating a high immediate safety risk. (MPG impact: 0%% · Added cost: $0 (Safety risk is the primary cost))
3. 2-6 months: If caused by a failing alternator, continued driving with unstable voltage permanently damages the battery and other sensitive electronic modules. (MPG impact: 1-5%% · Added cost: $500 - $2000)
4. 6+ months: Complete and permanent failure of the power steering system. Ignored wiring shorts cause thermal damage to the PSCM or other modules. (MPG impact: 0-5%% · Added cost: $1500 - $3000)

Cost of Not Fixing It

• Immediately: Sudden loss of power steering assist creates a major safety hazard. Steering becomes extremely heavy, increasing crash risk at low speeds or in emergencies. (Added cost: N/A (Safety Risk))
• 1-3 months: If caused by a faulty alternator, continued driving strains and damages other electronic modules due to unstable voltage, leading to a cascade of failures. (Added cost: $500-$2000)
• 3+ months: Driving with no power assist puts extra mechanical strain on steering components like the steering column and intermediate shaft. (Added cost: $300-$1500)

Diagnosis Steps

1. Verify Battery Health and Charging System
   Confirm the battery is healthy before any other step. Use a multimeter to check static battery voltage (>12.4V). Start the engine and check alternator output (13.2V to 14.8V). A weak battery is the most common root cause.
   Tools: Digital Multimeter (Beginner)
2. Comprehensive Code Scan
   Use an OBD-II scanner to read codes from ALL modules. A multitude of 'U' codes (e.g., U0100, U0121) indicates a systemic network or power issue. A solitary U1124 isolates the fault to the power steering system.
   Tools: OBD-II Scanner (with all-module capability) (Beginner)
3. Inspect Fuses and Relays
   Locate all fuses and relays related to the PSCM using the owner's manual. Visually inspect the fuses and test them with a multimeter for continuity.
   Tools: Owner's Manual, Multimeter, Fuse Puller (Beginner)
4. Physical Inspection of Wiring and Grounds
   Locate the PSCM on the steering rack or column. Inspect its wiring harness for physical damage, chafing, melting, or corrosion. Trace the main ground wire to the chassis and ensure it is clean, tight, and rust-free.
   Tools: Flashlight, Inspection Mirror (Intermediate)
5. Check for Power and Ground at the PSCM Connector
   Disconnect the PSCM connector. Identify the power and ground pins using a wiring diagram. With the ignition on, verify battery voltage at the power pins and near 0 ohms resistance to the chassis at the ground pins.
   Tools: Multimeter, Vehicle-specific Wiring Diagram (Advanced)
6. [PRO TIP] Live Data Analysis
   Access the live data stream (PIDs) from the PSCM using an advanced scan tool. Monitor 'PSCM Voltage Supply' and 'Steering Angle'. If you access this data, communication exists. If you cannot connect to the PSCM but other modules are online, the PSCM lacks power, ground, or has failed.
   Tools: Advanced Bi-Directional Scan Tool (Advanced)
7. [PRO TIP] CAN Bus Resistance Check
   With the battery disconnected, measure resistance between CAN High and CAN Low at the OBD-II port (Pins 6 and 14). A healthy network reads 60 Ohms. A 120-Ohm reading indicates an open circuit; significantly less than 60 Ohms indicates a short.
   Tools: Digital Multimeter, OBD-II Breakout Box (optional) (Advanced)
8. [PRO TIP] CAN Bus Voltage Check
   With the key on and engine off, measure CAN line voltage relative to chassis ground. CAN High (Pin 6) should be 2.6V - 2.7V. CAN Low (Pin 14) should be 2.3V - 2.4V. Significant deviation points to a network wiring fault.
   Tools: Digital Multimeter (with back-probes) (Advanced)
9. [PRO TIP] 5-Volt Reference Circuit Check
   Some EPS systems share a 5-volt reference circuit with other sensors. A shorted sensor (like a crank sensor) brings down the network. Unplug related sensors one by one to see if PSCM communication restores.
   Tools: Advanced Scan Tool, Wiring Diagram (Advanced)
10. Module Isolation and Condemnation
    If the PSCM has verified power, ground, and a healthy CAN bus network but fails to communicate, the module is dead. Replace and program the unit.
    Tools: Professional Diagnostic Tools (Professional)

When This Code Triggers (Freeze-Frame Conditions)

• Module Voltage: 11.8V - 14.8V (The voltage supplied to the PSCM is critical; the fault triggers during a low voltage event (e.g., engine cranking) or high voltage spike.)
• Vehicle Speed: 0 mph (at key-on) or any speed (The code sets immediately at key-on if the module doesn't check in, or during driving if communication is lost due to vibration or an intermittent wiring fault.)
• Ignition Status: Run or Start (The network communication check happens as soon as the key is in the 'Run' position. The fault logs if the PSCM fails to respond within a set time.)
• Network Status: Active (Freeze frame data indicates the state of the CAN bus, showing if the module was simply not responding on an otherwise healthy network.)

Related Codes

• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module. Often appears with U1124 during a general network or power issue. If only U1124 is present, the fault is isolated to the steering system.
• U0100 — Lost Communication With ECM/PCM 'A'. Indicates the vehicle's main computer is offline. Diagnosis must start with the ECM/PCM, not the steering module.
• C0051 — Steering Wheel Position Sensor. Indicates the PSCM is online but receiving an invalid signal from the steering angle sensor. U1124 means the entire PSCM is offline.
• P0606 — ECM/PCM Processor Fault. Indicates an internal failure of the main engine computer, which disrupts CAN bus communication and causes modules like the PSCM to set U1124.

Climate & Environmental Factors

• Road Salt / Humidity: Salt brine acts as an electrolyte, drastically accelerating the decay of wiring insulation, connector pins, and chassis ground points. This corrosion creates high resistance, leading to communication loss.
• Extreme Cold: Plastic wiring insulation and seals become brittle and crack in sub-zero temperatures, allowing moisture intrusion. Cold weather also maximizes battery voltage drops during engine cranking.
• Vibration and Heat: Constant engine bay vibration and heat cycles cause wires to chafe through their insulation or internal module components to fail from thermal stress.

How to Talk to a Mechanic About This Code

Say this: "I have a U1124 code and a loss of power steering. I've verified the battery and charging system are healthy. I need a diagnostic appointment to test the power, ground, and CAN bus signals at the Power Steering Control Module connector before considering a rack replacement."

This directs the shop to perform a logical diagnostic routine (checking wiring and connections) instead of immediately jumping to the most expensive conclusion (replacing the steering rack). It shows you understand the problem is often electrical.

Avoid saying:

• 'My steering is heavy, just fix it.'
• 'The power steering light is on, can you look at it?'
• 'I think I need a new power steering rack.'

Questions to ask before authorizing the repair:

• Did you verify 12V power and a solid ground at the PSCM connector itself?
• What were the CAN bus resistance and voltage readings at the OBD-II port and at the module?
• Can you confirm the module is failing to communicate despite having proper power, ground, and network connections?
• Does the quoted price for the replacement include mandatory programming and steering angle sensor calibration?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Necessary if the vehicle is under warranty or requires a dealer-exclusive software fix/programming. Otherwise, extremely expensive.
  Best for: Vehicles under warranty or covered by a recall/extended service program (e.g., Ford's 15N01)., Complex software issues on German brands (VW/Audi) requiring gateway coding., When a new module requires proprietary programming that aftermarket tools cannot perform.
  Downsides: Highest labor rates, often 40-50% more than independent shops., May default to replacing the entire expensive steering rack assembly rather than diagnosing a simpler wiring fault. (Typical cost: +40% vs. baseline)
• Independent Shop: Best fit for most out-of-warranty U1124 diagnostics. A shop with strong electrical skills finds and fixes common electrical causes for a fraction of the cost of a dealer rack replacement.
  Best for: Out-of-warranty vehicles where the cause is likely electrical (wiring, grounds, fuses)., Owners seeking a thorough diagnostic process before replacing expensive parts., Cost-conscious repairs utilizing lower labor rates and aftermarket part options.
  Downsides: Diagnostic skill varies widely; look for ASE certifications., May lack the latest manufacturer-specific programming tools, requiring a dealer visit for the final programming step. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID for U1124 diagnosis. They are ill-equipped to diagnose CAN bus communication failures, creating a high risk of misdiagnosis.
  Best for: Simple, unrelated maintenance like oil changes or tires.
  Downsides: Technicians lack specialized training for complex network diagnostics., Business model encourages replacing parts (battery/alternator) without full communication circuit diagnosis., Not equipped for module programming or advanced electrical troubleshooting. (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, seriously consider selling or trading in the vehicle.

• Car worth $5000, fix is $2200: Walk away. The repair cost is 44% of the car's value. Use that money as a down payment on a more reliable vehicle.
• Car worth $15000, fix is $2200: Fix it. The repair is 15% of the vehicle's value and is a worthwhile investment to keep a valuable car on the road.
• Car worth $3000, fix is $250: Fix it. If the issue is a simple wiring repair or fuse, the low cost makes it an easy decision.

What Scan Tool You Need for This Code

Minimum: A scanner that reads codes from ALL vehicle modules (ABS, SRS, BCM, PSCM), not just basic engine codes.

A cheap $20 code reader only checks engine codes and shows 'No Codes Found' for a U1124 fault. You must see which modules are online and which are not.

Budget: BlueDriver Pro or similar Bluetooth dongle (~$100) — Scans all vehicle systems to confirm which modules report the U1124 code. Allows viewing live data from responding modules.

Mid-range: Foxwell NT510/NT809BT, Autel MaxiCOM MK808S, Thinkcar Thinkscan 689BT (~$250-400) — Offers full system scanning and bidirectional controls. Crucial for actively testing components and commanding modules to isolate the communication breakdown.

Professional: Autel MaxiCOM MK906BT, Launch X431 series (~$500-1200) — Provides full bidirectional controls, advanced active tests, and ECU coding/programming. Can perform necessary programming after a PSCM replacement.

Rent vs buy: AutoZone's free Fix Finder service reads codes from systems like ABS for a one-time check. However, buying a midrange scanner is a wise investment for proper DIY electrical diagnosis.

How to Clear the Code After You Fix It

1. Ensure the root cause (e.g., wiring, fuse, module) is fixed.
2. Reconnect the battery if disconnected for repair.
3. Use a quality OBD-II scan tool to erase the U1124 code from all modules.
4. Perform a complete drive cycle to allow all system readiness monitors to run.

Drive cycle (~30 minutes): Perform a generic OBD-II drive cycle: a cold start (sit for 8+ hours), 2-3 minutes of idling, 10-15 minutes of mixed city driving, and 5-10 minutes of steady highway driving (55-60 mph). This verifies the repair and sets readiness monitors.

Readiness monitors affected: Comprehensive Component Monitor

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

Watch out for:

• Disconnecting the battery does not clear the code from all modules and resets all readiness monitors, causing an emissions test failure.
• If the underlying electrical issue (corroded ground or failing alternator) is not fixed, the code returns immediately.
• Forgetting to recalibrate the steering angle sensor or program the new module after replacement.

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. Clearing the code resets readiness monitors, preventing testing until they run again.
• New York: Any diagnostic trouble code that illuminates the Malfunction Indicator Lamp (Check Engine Light) causes an automatic failure of the OBD-II inspection.
• Texas: A Check Engine light commanded on by a DTC is an automatic failure. The vehicle must complete a drive cycle to set readiness monitors before re-inspection.

Most Commonly Affected Vehicles

• Ford F-150 (2011-2014) — Extremely common issue requiring replacement of the entire electronic power steering rack. Extended Warranty Program 15N01 covers this for 10 years/150,000 miles on many vehicles.
• Jeep Grand Cherokee (2011-2015) — Prone to CAN bus wiring issues and module failures. A failing alternator shorting out destroys the PCM, causing widespread communication issues.
• Chevrolet Silverado (2007-2013) — Known for power steering control module and wiring failures in high-mileage vehicles. Poor ground connections on the frame are a frequent cause.
• Dodge Ram 1500 (2013-2018) — Failures in the electronic power steering (EPS) rack assembly are a known issue, often preceded by a whining noise from the steering system.
• Volkswagen/Audi Tiguan, Golf, A3, TT (2015-2020) — Prone to software issues or incorrect gateway coding causing a 'U112400 - Data bus Additional Installations detected' fault after a battery change.
• Hyundai Sonata, Elantra (2011-2017) — Subject to warranty extensions (e.g., TXXO for 2015-2017 Sonata) for EPS motor or control module failures causing sudden loss of steering assist.
• BMW 3-Series (E9x), 5-Series (E6x) (2006-2013) — A failing Intelligent Battery Sensor (IBS) or alternator causes widespread, intermittent communication faults across the vehicle network.
• Jeep Wrangler (4xe) (2021-2024) — A failing 12V auxiliary battery causes numerous, seemingly unrelated electronic faults and communication codes.

Manufacturer-Specific Notes

• Toyota/Lexus: On some models, U1124 refers to 'Lost Communication with Right Headrest Control ECU' for the active headrest system, completely unrelated to power steering. Verify the code definition with a manufacturer-specific tool.
• General Motors (GM): GM issued 'Special Coverage Programs' (e.g., bulletin 15356) providing extended warranties for torque sensors and motor modules. Diagnosing CAN bus issues on newer GM vehicles requires the GDS 2 diagnostic tool.
• Chrysler/Jeep/Dodge (Stellantis): TSB S2208000027 REV. B notes that on some hybrid models, U1124 sets alongside P0E15 and U1008, pointing to an issue in the high-voltage coolant heating system, not the power steering.
• Ford: Safety Recall 15S18 and Extended Warranty Program 15N01 cover PSCM reprogramming or steering gear replacement for up to 10 years or 150,000 miles on a wide range of models.
• Volkswagen/Audi: A fault of 'U112400 - Data bus Additional Installations detected' occurs if a module is incorrectly coded in the CAN Gateway after a battery change. The fix is re-coding the gateway installation list.
• Hyundai: Hyundai extended the warranty for the Motor Driven Power Steering (MDPS) assembly on certain 2015-2017 Sonata models to 15 years / 150,000 miles under campaign TXXO.

How to Prevent This Code From Triggering

• Apply dielectric grease to the PSCM electrical connector seals. (Once, or whenever the connector is disconnected.) — Dielectric grease is a waterproof paste that seals out moisture, preventing corrosion on connector pins—a primary cause of communication loss.
• Perform regular battery and charging system tests. (Annually, especially before winter.) — The EPS system is highly sensitive to voltage. A weak battery causes low voltage (<12.4V), leading to intermittent communication dropouts.
• Clean battery terminals and main chassis ground points. (Every 2-3 years or as needed.) — Corrosion on battery terminals or the main chassis ground strap creates resistance, causing voltage drops to critical modules like the PSCM.
• Inspect and secure wiring harnesses. (During any under-hood maintenance.) — Visually checking the wiring harness for chafing and securing loose harnesses with zip ties prevents vibration-induced damage that leads to shorts.

Frequently Asked Questions

Can I drive my car with a U1124 code?

No. The power steering fails without warning, requiring a massive increase in physical effort to control the vehicle. This is extremely dangerous and the vehicle should only be towed to a repair shop.

How much does it cost to fix U1124?

Costs range from $10 for a simple fuse to $100-$300 for wiring repairs. If the entire power steering rack requires replacement, expect bills between $800 and $2,500 including mandatory programming.

Can a bad battery cause this code?

Yes, a weak battery is a primary cause of U1124. Electronic power steering modules require stable voltage and drop offline during voltage dips. Always test the battery and alternator before replacing expensive parts.

What's the difference between U1124 and a C-code for steering?

'U' codes (like U1124) indicate network communication problems, meaning the module is offline. 'C' codes (like C0051) indicate chassis faults, meaning the module is online but detects a sensor or circuit problem.

I replaced the battery and now I have this code. What happened?

Voltage drops during battery replacement often trigger false communication faults. Clear the codes with an OBD-II scanner to see if they return. If U1124 persists on German vehicles like VW/Audi, the CAN gateway requires dealer re-coding.

What is the most common misdiagnosis for U1124?

The most frequent mistake is immediately replacing the expensive Power Steering Control Module (PSCM) or steering rack. The actual fault is usually a weak battery, a corroded ground wire, or a blown fuse.

Is the Power Steering Control Module the same as the power steering pump?

No. This code applies to vehicles with Electric Power Steering (EPS), which use an electric motor and a control module. Older hydraulic systems use a belt-driven pump and do not have a PSCM.

Key Takeaways

• Code U1124 indicates a total communication loss with the Power Steering Control Module (PSCM), instantly disabling electric power steering assist.
• Test the battery and alternator first; voltage drops below 12.4V are the leading cause of U1124, not a failed steering rack.
• Never replace the $1,000+ steering rack without first verifying 12V power, solid ground, and 60-ohm CAN bus resistance at the module connector.
• Do not drive with an active U1124 code; the sudden requirement for heavy manual steering effort causes a severe crash risk at low speeds.
• Repair costs range from $10 for a blown 50-amp EPS fuse to over $2,000 for a complete steering rack replacement and dealer programming.