C0499 – Steering Assist Control Solenoid Feed Circuit High

System: Chassis | Standard: ISO/SAE Controlled | Fault type: Circuit High

Official meaning: Steering Assist Control Solenoid Feed Circuit High

Definition source: SAE J2012 naming/structure guidance

What Does C0499 Mean?

C0499 – Steering Assist Control Solenoid Feed Circuit High is an ISO/SAE controlled chassis DTC that indicates the vehicle has detected a circuit high condition on the steering assist control solenoid feed circuit. The official meaning is: Steering Assist Control Solenoid Feed Circuit High.

This code sets when the control module responsible for steering assist determines the monitored feed circuit voltage (or equivalent circuit state feedback) is higher than the allowed range for the current operating condition. A “circuit high” fault points to an electrical condition such as short-to-voltage, unintended backfeed, an open/high-resistance condition that causes a measured point to float high, or a control/driver monitoring issue. It does not, by itself, prove that the solenoid is defective; it specifically indicates the feed circuit is being interpreted as high.

Quick Reference

• Code: C0499
• Official Title: C0499 – Steering Assist Control Solenoid Feed Circuit High
• Official Meaning: Steering Assist Control Solenoid Feed Circuit High
• System: Chassis
• Standard classification: ISO/SAE Controlled
• Fault type: Circuit High
• What it indicates: The steering assist control solenoid feed circuit is being detected as higher than expected
• Primary diagnostic focus: Feed circuit voltage integrity, shorts to voltage, connector/terminal condition, wiring integrity, and module-side monitoring/driver checks

Symptoms

When C0499 is present, one or more of the following symptoms may occur depending on how the steering assist system responds to the detected circuit high condition:

• Steering assist warning indicator/message: A steering-related warning may illuminate and the DTC may store.
• Reduced steering assist: Increased steering effort, most noticeable during low-speed maneuvers.
• Intermittent assist changes: Assist may vary if the electrical fault is intermittent.
• Failsafe operation: The system may limit or disable assist to protect components when a circuit fault is detected.
• Steering feel not consistent: Assist level may not match expected behavior during turning inputs.

Common Causes

C0499 is a circuit high DTC, so causes are centered on conditions that make the feed circuit read/behave as higher than intended. Common causes include:

• Short to voltage on the steering assist control solenoid feed circuit due to damaged insulation, pinched wiring, or contact with a powered circuit.
• Unintended backfeed into the feed circuit from an incorrect splice, misrouted repair, or cross-connection to another circuit.
• Connector terminal problems (corrosion, moisture intrusion, bent pins, loose pin fit, pushed-out terminals) that alter circuit behavior and can lead to a high reading.
• Open circuit or high resistance in the feed circuit that may allow the monitored point to float high depending on the circuit design and module monitoring strategy.
• Power supply issues affecting the steering assist system that can contribute to abnormal high voltage on the monitored circuit.
• Steering assist control solenoid electrical fault (internal failure) that influences feed circuit behavior.
• Control module driver/monitor fault where the module incorrectly detects or reports the circuit as high after all external circuit checks pass.

Diagnosis Steps

Diagnosis should follow the wiring diagram and service information for the exact vehicle configuration. Use a scan tool capable of accessing chassis/steering data, a digital multimeter, and appropriate back-probing/terminal test tools. Observe all safety precautions when working near steering components and moving parts.

1. Confirm the DTC and capture data: Scan for C0499 and any related chassis, voltage, or communication DTCs. Save freeze-frame/event data and note whether the code is current or history.
2. Identify the exact circuit path: Using the wiring diagram, locate the steering assist control solenoid feed circuit, associated connectors, splices, grounds (if applicable), and the control module pins involved.
3. Perform a visual inspection: Inspect the harness routing from the module to the solenoid for chafing, pinch points, melted insulation, abrasion near brackets, and any signs of previous repairs.
4. Inspect connectors and terminals: Check both the solenoid-side and module-side connectors for corrosion, moisture, bent pins, pushed-out terminals, or loose terminal tension. Ensure connectors are fully seated and locked.
5. Check system power integrity: Verify related fuses/relays and power feeds for the steering assist system. Confirm battery voltage is stable and within specification with the engine running and key-on conditions as required by service procedures.
6. Measure feed circuit voltage: With reference to the wiring diagram, measure the feed circuit at the solenoid connector and (as needed) at the module connector. Compare observed values to what is expected for the commanded state (on/off/modulated) rather than assuming a universal threshold.
7. Test for short to voltage: Isolate the circuit as directed (disconnect the solenoid and, if required, the control module connector). Check for unintended continuity between the feed circuit and B+ or other powered circuits.
8. Check for open/high resistance: Perform end-to-end continuity/resistance checks on the feed circuit. Where applicable, use a load test or voltage drop method to identify high resistance that may not appear during a simple ohms check.
9. Use bi-directional controls if available: Command steering assist control solenoid operation (when supported) and monitor relevant PIDs/status indicators to see whether the circuit state follows commands or remains stuck high.
10. Intermittent fault checks: While monitoring circuit state, gently wiggle the harness and connectors at known movement points to identify changes that indicate a poor connection or internal conductor break.
11. Evaluate module involvement only after circuit verification: If the wiring, connectors, power supply, and solenoid checks meet specifications but C0499 persists, follow the manufacturer’s pinpoint tests for module driver/monitoring. Consider programming or module replacement only when directed by confirmed test results.

Possible Fixes

Repairs should be based on verified test results and must correct the circuit high condition on the steering assist control solenoid feed circuit. Possible fixes include:

• Repair or replace damaged wiring in the steering assist control solenoid feed circuit (chafed insulation, pinched harness, heat damage) and restore proper routing/retention.
• Correct short-to-voltage or backfeed conditions by removing incorrect splices, repairing cross-connected circuits, and restoring the wiring to the correct configuration.
• Service connectors and terminals: Clean and dry contaminated connectors, repair terminal fit issues, and replace corroded/damaged terminals as required.
• Restore proper power supply integrity by repairing fuse/relay contacts, power feed issues, or other identified voltage supply problems affecting the steering assist system.
• Replace the steering assist control solenoid only if electrical testing confirms it is out of specification and the feed circuit is verified good.
• Repair/replace and configure the control module only after completing circuit checks and following the specified module diagnostic procedure (including any required setup/calibration steps).

Can I Still Drive With C0499?

C0499 involves the steering assist system, so drivability depends on whether steering assist is reduced, inconsistent, or disabled. If steering effort is increased or assist is unpredictable, operating the vehicle may require more steering input than expected, especially during low-speed maneuvers.

If you experience heavy steering, fluctuating assist, or steering warning messages, limit driving and have the fault diagnosed as soon as possible. If steering assist feels normal and the code is stored without noticeable changes, the vehicle may still be operable, but the underlying circuit high condition should be addressed promptly due to the safety relevance of steering assist operation.

Repair Costs

Repair cost depends on whether the confirmed root cause is wiring, connector condition, a switch or module issue, or the labor needed to diagnose the fault correctly.

Related Steering Solenoid Codes

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