What Does C0691 Mean?
This code indicates the control module has detected an abnormal voltage or resistance value in the damper control relay circuit, which is part of the electronically controlled suspension system. The relay controls power to the adaptive or variable damping system actuators that adjust shock absorber stiffness. The control module detected a circuit value outside the expected operating range, suggesting a fault in the relay, its wiring, or the control circuit.
Common Causes
35%
Faulty damper control relay with internal coil or contact failure
30%
Open or short circuit in relay control wiring harness between control module and relay
20%
Corroded or damaged relay connector terminals causing high resistance
10%
Failed suspension control module relay driver circuit
5%
Poor ground connection at relay or control module
Diagnostic Steps
1
Step 1: Locate the damper control relay (typically in engine bay fuse/relay box or under-dash panel). Visually inspect the relay and its connector for physical damage, corrosion, melted terminals, or signs of overheating.
2
Step 2: With ignition off, remove the relay and test it using a multimeter. Measure coil resistance (typically 70-120 ohms) across control terminals, then apply 12V to energize the relay and verify audible click and continuity across switched terminals.
3
Step 3: With relay removed and ignition on, use multimeter to check for battery voltage at relay socket power supply terminal and proper ground at ground terminal. Check for control signal voltage from module (should vary between 0-12V when commanded).
4
Step 4: Inspect wiring harness from relay socket back to suspension control module for chafing, pinching, or damage. Test continuity of control circuit wire and power/ground circuits, checking for shorts to ground or power (should read >10k ohms to ground when disconnected).
5
Step 5: If all wiring and relay test good, suspect control module relay driver failure. Check technical service bulletins for known module issues. Verify proper voltage supply and grounds to control module itself.
6
Step 6: After repair, clear codes, cycle ignition, and perform active test of damper system using scan tool functions. Road test vehicle over various surfaces to verify adaptive damping response and confirm code does not return.
Estimated Repair Cost
$150 - $650
Parts + labor, varies by vehicle and location
This code indicates the control module has detected an abnormal voltage or resistance value in the damper control relay circuit, which is part of the electronically controlled suspension system. The relay controls power to the adaptive or variable damping system actuators that adjust shock absorber ...
The most common cause of C0691 (Damper Control Relay Circuit Range) is: Faulty damper control relay with internal coil or contact failure
Typical repair costs for C0691 range from $150 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but will operate with reduced suspension performance in failsafe mode (typically fixed damping). Ride quality and handling will be degraded, especially on rough roads or during aggressive driving, but vehicle remains controllable. Repair within a few weeks to restore optimal suspension function.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C0691 to identify the root cause.
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Quick Info
Category
Chassis
System
Electronic Suspension Control System
Difficulty
Type
Generic (SAE)
Recommended Tools
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