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C0604 — Active Air Dam Control Circuit Performance

Generic OBD-II · all makesChassis

C0604 indicates the active air dam control circuit is not performing as expected. The active air dam is a movable front aero device, and the code is set when the module sees an actuator or feedback-circuit fault that prevents proper deployment or retraction.

Symptoms

What causes it — most likely first

1. Failed active air dam actuator/motor assembly

The actuator motor, gears, or linkage can bind, burn out, or mechanically fail. This is the most common cause because the moving components operate in a harsh road-splash and debris environment.

2. Wiring or connector damage in the air dam circuit

Harnesses routed near the front bumper can chafe, corrode, or lose pin tension from vibration and moisture. An open, short, or high-resistance circuit causes the control performance fault.

3. Faulty air dam position sensor

Many systems use an internal position sensor to verify movement. A failed sensor or incorrect feedback signal makes the module think the actuator is not moving correctly.

4. Poor power or ground supply

A weak battery, loose ground eyelet, or corroded fuse/relay feed can reduce voltage to the actuator, causing slow or incomplete movement and a circuit-performance code.

5. Control module failure

The active air dam control module or chassis module commanding the actuator can fail, but this is uncommon. It should be considered only after the actuator, wiring, sensor, and power/ground are verified good.

How it's diagnosed

  1. Retrieve all codes and freeze-frame data, then clear codes and command the active air dam on and off with a scan tool to see if it operates
  2. Visually inspect the air dam actuator, linkage, and front bumper harness for physical damage, water intrusion, corrosion, or chafing
  3. Check battery voltage and test power, ground, and control-signal circuits at the actuator connector during commanded operation
  4. Compare commanded position to actual feedback data; if the actuator moves but feedback does not change, suspect the internal position sensor or actuator assembly
  5. If all electrical and mechanical tests pass, evaluate the control module only as a last step

Code facts & related codes

SystemChassis
StandardizationSAE generic — identical on every make
Related codesC0600 — 4Wdawd Range Actuator Position ControlC0601 — Active Air Dam Control CircuitopenC0602 — Active Air Dam Control Circuit LowC0603 — Active Air Dam Control Circuit HighC0605 — Steering Wheel Angle Sensor CircuitopeC0606 — Steering Wheel Angle Sensor Circuit Lo

Frequently asked

Is it safe to drive with C0604?

Yes. The code affects the active front aero dam, not engine or braking performance. The vehicle remains drivable, though highway fuel economy may be slightly reduced.

Can I replace just the motor, or do I need the whole air dam actuator?

That depends on the vehicle design. Many systems require the actuator or air dam assembly as a unit because the motor, gears, and sensor are not separately serviceable. Check the service procedure for your specific model.

My mechanic said I need a new PCM. Is that true?

Usually not. The PCM or active air dam control module is rarely the cause of C0604. Most faults are in the actuator, wiring, connector, or position sensor. Replacing the module before verifying the circuit and actuator is usually the wrong repair.

Why did the warning come on after driving through water or snow?

Water, ice, and road salt can get into the actuator or connector, causing corrosion, binding, or a temporary short. Drying out and inspecting the connector may resolve the issue, but damage may remain if corrosion has set in.