C0660 – Level Control Exhaust Valve Circuit Malfunction

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

Official meaning: Level Control Exhaust Valve Circuit Malfunction

Definition source: SAE J2012 naming/structure guidance

What Does C0660 Mean?

C0660 – Level Control Exhaust Valve Circuit Malfunction is an ISO/SAE controlled chassis diagnostic trouble code that indicates the vehicle has detected a circuit malfunction in the electrical circuit for the level control exhaust valve. This is a circuit-level fault designation, meaning the controller has identified abnormal electrical behavior in the exhaust valve circuit (such as an open, short, high resistance, or improper operation of the circuit) rather than proving a specific mechanical failure.

The level control exhaust valve is used to vent air (or release pressure) as part of an automatic leveling or air suspension height-control strategy. When the circuit malfunction is detected, the system may be unable to vent as commanded, may disable leveling functions, or may operate with limited capability depending on how the controller is programmed.

Quick Reference

• Code: C0660
• Official Title: C0660 – Level Control Exhaust Valve Circuit Malfunction
• Official Meaning: Level Control Exhaust Valve Circuit Malfunction
• System: Chassis
• Fault Type: Circuit
• Standard Classification: ISO/SAE Controlled
• What it points to: Electrical circuit issue affecting the level control exhaust valve control/monitoring circuit

Symptoms

When C0660 is present, the most noticeable effects are tied to height control and the system’s ability to vent pressure. Symptoms can vary depending on whether the fault is intermittent or continuous.

• Warning indicator/message: A chassis or suspension-related warning may illuminate and height control may be limited or disabled.
• Ride height not adjusting correctly: The vehicle may not lower when commanded, or may not return to a target height after a load change.
• Uneven stance: The vehicle may sit unevenly if the system cannot properly manage venting and leveling actions.
• Ride quality changes: Harshness, excessive firmness, or altered ride feel can occur if pressure and height are not regulated as intended.
• Height changes that are intermittent: Operation may come and go if the circuit fault is due to a loose terminal, corrosion, or harness movement.
• Additional chassis DTCs: Other level control or suspension-related codes may store if the system cannot achieve expected results.

Common Causes

C0660 is a circuit malfunction code, so causes are primarily electrical. The items below describe faults that can produce abnormal circuit behavior in the level control exhaust valve circuit.

• Wiring damage: Chafed, pinched, stretched, broken, or corroded wiring in the exhaust valve circuit.
• Connector/terminal problems: Loose connectors, water intrusion, corrosion, bent pins, spread terminals, or poor terminal tension at the exhaust valve or along the harness.
• Power supply issue: Missing or unstable power feed to the level control system that prevents proper circuit operation (for example: fuse/relay or high-resistance feed).
• Ground integrity issue: High resistance or intermittent ground path that causes incorrect voltage/current behavior in the circuit.
• Exhaust valve electrical fault: Solenoid/actuator internal electrical issue (open circuit, short circuit, or resistance out of specification).
• Short to power/short to ground: Circuit conductor contacting power, ground, or another circuit causing abnormal readings or driver protection shutdown.
• Controller driver/monitoring fault: Internal failure of the control module output driver or circuit monitoring (consider only after circuit and component checks).

Diagnosis Steps

Accurate diagnosis requires access to chassis/level control diagnostics, a wiring diagram for the exact vehicle configuration, and electrical test equipment. The goal is to confirm the fault is in the level control exhaust valve circuit and identify whether the problem is wiring, terminals, the exhaust valve electrical component, power/ground, or the control module driver/monitoring.

1. Confirm the code and capture data: Scan the chassis/level control module for C0660 and record freeze-frame or environment data (if available). Note whether the code is current, pending, or history.
2. Check for related chassis codes: If other level control, voltage, or communication codes are present, address those that indicate shared power/ground or module supply issues first.
3. Perform a visual inspection of the circuit path: Inspect harness routing to the exhaust valve area for rubbing, pinching, prior repairs, or contact with moving suspension components.
4. Inspect connectors and terminals: Disconnect and inspect the exhaust valve connector and any inline connectors. Look for corrosion, moisture, damaged locks, bent pins, push-outs, or poor pin fit.
5. Verify power and ground: Using the wiring diagram, confirm the correct supply voltage and ground are present for the circuit. Prefer voltage-drop testing under load over simple continuity checks where possible.
6. Check circuit for opens/shorts: With the system powered down as required, test continuity end-to-end and check for shorts to ground or shorts to power on the control and supply circuits associated with the exhaust valve.
7. Command the exhaust valve (if supported): Use bidirectional controls to command the exhaust valve on/off. Observe whether the module accepts the command and whether circuit activity changes as expected.
8. Measure circuit behavior at the valve connector: With appropriate safety precautions, verify the presence of the expected power/ground and switching/control signal at the exhaust valve connector according to the circuit design.
9. Test the exhaust valve electrically: Measure solenoid/actuator resistance and compare to specification for the exact component. An open, short, or out-of-spec reading supports component replacement.
10. Evaluate the control module only after circuit/component checks: If wiring, terminals, power/ground, and exhaust valve electrical tests all pass, investigate module-side driver/monitoring faults and connector pin fit at the module.
11. Clear codes and verify the repair: After repairs, clear DTCs and run the system through a functional check or drive cycle appropriate for the level control system to confirm C0660 does not return.

Possible Fixes

Repairs for C0660 should be based on test results that confirm the exact circuit fault.

• Repair/replace wiring: Correct opens, shorts, high-resistance sections, damaged insulation, or poor splices in the level control exhaust valve circuit.
• Repair connector/terminal issues: Clean and dry moisture-contaminated connectors, replace corroded terminals, restore terminal tension, and ensure connectors are fully seated and locked.
• Restore power supply: Replace failed fuses/relays or repair power-feed wiring issues after identifying and correcting the root cause of the electrical fault.
• Restore ground integrity: Clean/repair ground points, repair broken ground wires, and confirm acceptable voltage drop under load.
• Replace the exhaust valve component (electrical failure confirmed): Replace the level control exhaust valve solenoid/actuator if electrical testing verifies it is defective.
• Address control module faults (only if proven): If all external circuit checks pass and testing supports an internal driver/monitoring fault, repair or replace the applicable control module per manufacturer procedure.

Can I Still Drive With C0660?

Driving with C0660 may be possible, but it depends on whether the vehicle maintains a stable and safe ride height and handling response. Because this is a chassis system code involving level control, the vehicle may not adjust height correctly or may disable leveling functions to protect the system.

Do not continue driving if the vehicle is excessively low or high, leans noticeably, bottoms out, contacts the body/underbody, or exhibits unstable handling. If the vehicle remains at a normal height and behaves predictably, short-distance driving may be possible while you schedule diagnosis, but avoid heavy loads and operating conditions that require the level control system to function correctly.

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 Valve Level Codes

Compare nearby valve level trouble codes with similar definitions, fault patterns, and diagnostic paths.

• C0663 – Level Control Exhaust Valve Circuit High
• C0662 – Level Control Exhaust Valve Circuit Low
• C0254 – EBCM Control Valve Circuit
• C0241 – EBCM Control Valve Circuit
• C0175 – Brake Fluid Level Sensor Circuit
• C0691 – Damper Control Relay Circuit Range