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DTC codes / C05xx · Brakes, steering and suspension / C05D6

C05D6Power Steering Control Module Processor Performance

This code indicates that the Power Steering Control Module (PSCM) has detected an internal processor performance fault, meaning the module's central processing unit is not executing instructions correctly or is failing self-tests. The module sets this code when its internal diagnostics reveal that the processor is not running at the expected speed, has memory integrity errors, or cannot reliably perform its control calculations for the electric power steering system.

SystemChassis
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaBrakes, steering and suspension

Symptoms you may notice

  • The power steering warning light illuminates on the dashboard, often accompanied by a chime.
  • The steering may feel heavier or require more effort, especially at low speeds.
  • The power steering assist may cut out intermittently or be completely disabled.
  • The steering wheel may return to center more slowly or feel less responsive.
  • Often no symptoms besides the warning light, with steering performance seemingly normal.
  • In some cases, the vehicle may enter a fail-safe mode that limits engine power or other functions.

Common causes, most likely first

  1. Internal failure of the Power Steering Control Module processor or its supporting circuitry.
  2. Corrupted software or firmware in the PSCM due to a failed update or memory corruption.
  3. Low or unstable battery voltage causing the processor to malfunction or reset unexpectedly.
  4. Poor electrical connections at the PSCM connectors, including corrosion or loose pins.
  5. Ground fault or voltage drop in the power or ground circuits feeding the PSCM.
  6. Overheating of the PSCM due to prolonged heavy steering load or a cooling system issue.
  7. Water intrusion into the PSCM housing, leading to circuit board damage.

How to diagnose and fix it

  1. Verify battery voltage and charging system performance; a weak battery can cause spurious processor codes.
  2. Inspect the PSCM connectors and wiring for corrosion, loose pins, or damage; clean and secure as needed.
  3. Check power and ground circuits to the PSCM for voltage drops and continuity using a multimeter.
  4. Perform a scan tool check for any available software updates or recalibration procedures for the PSCM.
  5. Clear the code and test-drive the vehicle to see if the code returns; if it does, proceed with module diagnostics.
  6. If all external factors are ruled out, replace and reprogram the Power Steering Control Module.
  7. After replacement, perform any required calibration or initialization procedures for the steering system.

Processor Faults Often Misdiagnosed as Sensor Issues

  • A processor performance code can be set by a momentary voltage dip during engine cranking, so always check for a weak battery before condemning the module.
  • Many technicians replace the PSCM only to find the code returns because a poor ground connection at the chassis or engine block was the real culprit.
  • This code does not always mean the module is dead; it can be stored by a one-time glitch that never recurs, so clearing and retesting is a valid first step.
  • Aftermarket electrical accessories or improper jump-starting can introduce voltage spikes that corrupt the processor's memory, leading to this code.
  • Some vehicles require a software reflash of the PSCM to address known processor performance issues, so always check for technical service bulletins before replacing hardware.

Can I keep driving with C05D6?

If the power steering assist is still working, you can drive cautiously to a repair shop, but avoid high speeds and heavy steering maneuvers. If the steering assist has failed or the wheel feels very heavy, stop driving and have the vehicle towed to prevent loss of control.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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