Code
C0499
HUMMER
C — Chassis
Steering Assist Control Solenoid Feed Circuit High
Views:
UK: 12
EN: 8
RU: 7
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the solenoid feed circuit
- Faulty steering assist control solenoid (internal short or incorrect resistance)
- Poor, corroded, or damaged connector or wiring (insulation damage, pin pushed out)
- Faulty power/steering control module or ECU output transistor
- Blown or incorrectly rated fuse/relay feeding the solenoid circuit
- Aftermarket modifications or incorrect parts installed
Symptoms
- Reduced or intermittent power steering assist (harder steering)
- Illumination of the power/steering warning lamp and/or ABS/ESP lamp
- Stored/active C0499 trouble code and possible related chassis codes
- Possible steering assist fallback mode or limp steering behavior
- Noisy or unusual operation from steering assist pump or motor (if applicable)
What to check
- Read and record freeze frame and related codes (scan tool)
- Check battery voltage and charging system (battery >12 V with key on; 13.5–14.8 V when running)
- Inspect fuses and relays for the steering assist/solenoid feed circuit
- Visually inspect connectors and wiring for the steering assist solenoid for corrosion, damage, or pushed-out pins
- Backprobe solenoid feed connector and measure voltage with key ON and while commanding assist with a scan tool
- Check continuity and resistance of the solenoid coil (compare to spec)
Signal parameters
- Nominal battery voltage at feed: ~12.0–14.8 V (key on/engine running)
- High/circuit fault threshold: voltage significantly above expected reference or stuck at battery with no command (varies by vehicle)
- Typical solenoid coil resistance (example): 2–20 ohms depending on design — consult vehicle wiring/repair manual for exact spec
- Expected command signal: DC switching (on = feed applied, off = no feed) or PWM depending on system — use scope for waveform verification
Diagnostic algorithm
- Retrieve freeze frame and all stored codes; note conditions when C0499 set (vehicle speed, engine load, voltage).
- Verify battery/charging system is within spec; low or highly fluctuating voltage can create false readings.
- Visually inspect harness and connector at the steering assist solenoid and at the steering/power control module for damage, corrosion, or loose pins. Repair any obvious issues.
- Check fuses/relays in the solenoid feed circuit; replace if suspect.
- With key ON (engine off), backprobe the solenoid feed pin and measure voltage. If voltage is high when it should be low, suspect short to B+. If it is low when commanded, suspect open.
- Measure solenoid coil resistance at the connector; compare to vehicle spec. If out of range, remove and bench-test/replace solenoid.
- Perform a wiggle test on wiring while monitoring voltage or live data to spot intermittent shorts or opens.
- If wiring and solenoid check good, test the output driver at the steering control module: check for shorts to battery at module output and for correct switching using a scope or DVOM while commanded by a scan tool.
- If module output is stuck high and wiring/solenoid ok, consider module repair or replacement per manufacturer procedure. Reprogram or configure replacement modules as required.
- Clear codes, perform functional test/road test, and verify code does not return.
Likely causes
- Wiring short to B+ at or near the solenoid connector
- Corroded connector causing an intermittent high voltage reading
- Failed solenoid with internal short to battery potential
- Powertrain/steering control module output stage shorted or failed
- Loose or missing ground causing circuit reference shift
Fault status
Status
Steering Assist Control Solenoid Feed Circuit High — the control module detected an over-voltage/high condition on the solenoid feed circuit. This may cause reduced or no steering assist and requires inspection of wiring, connectors, solenoid, fuses, and the control module.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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