When the third engine‑cooling fan does not spin, the dash may flash a “Fan 3” warning lamp and the temperature gauge can climb toward the red zone. Drivers often notice the fan silence most strongly after a stop‑and‑go commute, during a prolonged idle, or on a hot day when the engine temperature spikes. In some cases the check‑engine light appears with the P0695 code stored, indicating that the ECM has logged a low‑voltage condition on the fan‑control circuit. Early detection is crucial because a non‑functioning fan can lead to overheating, coolant boil‑off, and long‑term engine damage.
The ECM supplies a ground‑side or +12 V control signal to the fan‑control relay or driver. If the internal driver transistor fails, the voltage presented to the circuit can drop below the required threshold (typically < 5 V), triggering P0695.
A broken wire, corroded connector pin, or high‑resistance splice in the fan‑3 control line can reduce voltage at the fan motor. Resistance above 2 Ω often causes the ECM to read a low‑voltage condition.
Many vehicles use a dedicated relay or a fan‑control module that switches the high‑current fan motor. A stuck or internally failed relay may present an open circuit to the ECM, resulting in the low‑circuit code.
If the fan‑motor’s internal driver draws excessive current (e.g., due to bearing wear or winding damage), the voltage at the control line can sag, prompting the ECM to log P0695.
Occasionally, an outdated ECM calibration can misinterpret normal voltage fluctuations as a fault. Re‑flashing the ECM with the latest software may resolve the false low‑circuit reading.
Use a professional scan tool to read the P0695 code and capture freeze‑frame parameters (engine coolant temperature, fan‑control voltage, and engine speed). Verify that the ECM commanded fan 3 at the time of the fault.
Locate the fan‑3 control harness from the ECM to the fan‑control relay. Check for frayed insulation, broken pins, corrosion, or loose crimp connections. Repair any damaged sections before proceeding.
With the ignition on and the engine at operating temperature, measure the voltage on the fan‑3 control wire relative to ground. A healthy signal should be approximately 12 V (or a solid ground if the circuit is ground‑side). Readings below 5 V confirm a low‑circuit condition.
Disconnect the control wire from the ECM and perform a continuity test between the connector pin and the relay input terminal. Resistance greater than 2 Ω indicates an open or high‑resistance path.
Swap the fan‑3 relay with a known good relay of the same type (if the vehicle uses a separate relay). Listen for the relay click when the ECM commands the fan. If the relay clicks but the fan still does not run, the fault likely lies in the fan‑motor driver or the ECM output.
Apply direct 12 V power to the fan‑3 motor terminals (bypassing the control circuit) to confirm the motor spins. If the motor fails to run, replace the fan‑motor assembly; otherwise, the control circuit is at fault.
With the relay removed, measure voltage at the ECM output pin while the ECM commands fan 3. A stable 12 V (or ground) confirms the ECM driver is functional. An intermittent or low reading points to a failing ECM output stage.
If all hardware tests are satisfactory, re‑flash the ECM with the latest manufacturer software. Many scan tools can perform this update; verify that the P0695 code does not reappear after the update.
– Wiring or relay repair: Typically $50‑$150 for parts and labor.
– Fan‑motor replacement: $150‑$300 plus labor.
– ECM or dedicated fan‑control module replacement: $600‑$900 for the module, $200‑$300 labor, plus programming.
Replace the ECM or fan‑control module only after confirming that wiring, relay, and fan‑motor are functional, as these modules are expensive and require VIN‑matched programming.
Service Recommendation: Most issues related to this fault are diagnosed and corrected through inspection, wiring repair, and calibration rather than module replacement. For modules not typically replaced through aftermarket suppliers, diagnosis and repair should be performed by a certified automotive technician with access to factory service information and tooling.