Powertrain Control Module (PCM)

P0691-COOLING FAN 1 CONTROL CIRCUIT LOW





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The cooling fan is a hydro-electric controlled device that is engine mounted. The Powertrain Control Module (PCM) monitors various sensors to control fan speed. The cooling fan provides temperature control for engine coolant, engine charged air, A/C Freon and automatic transmission fluid. Fan speed increases as cooling requirements increase. Since the fan is mounted to the engine, fan speed is related to engine speed (RPM). The PCM uses a Pulse Width Modulated (PWM) driver to control the amount of fluid to the clutch fan. When the fan is fully engaged it is capable of speeds about 10% greater than engine speed. The fan will rotate anytime the engine is running, even when the PCM is not sending a PWM signal.

- When Monitored:
When the ignition is on.

- Set Condition:
When the control coil is electrically shorted or open.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on.
2. Using the scan tool, erase DTCs.
3. Turn the ignition off for 75 seconds.
4. Turn the ignition on.
5. Using the scan tool, actuate the Radiator Clutch Fan control on.
6. Using the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Perform the INTERMITTENT DTC diagnostic procedure. Intermittent Condition Test

2. CHECK THE (K161) CLUTCH FAN SUPPLY CIRCUIT FOR A SHORT TO GROUND




1. Stop actuation of the Radiator Clutch Fan.
2. Disconnect the Radiator Clutch Fan harness connector.
3. Disconnect the PCM C1 harness connector.
4. Measure the resistance between ground and the (K161) Clutch Fan Supply circuit at the Radiator Clutch Fan harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the (K161) Clutch Fan Supply circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK FOR THE (K161) CLUTCH FAN SUPPLY CIRCUIT SHORTED TO THE (K971) ACTUATOR GROUND CIRCUIT




1. Measure the resistance between the (K161) Clutch Fan Supply circuit and the (K971) Actuator Ground circuit at the Radiator Clutch Fan harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the short between the (K161) Clutch Fan Supply circuit and the (K971) Actuator Ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE RADIATOR CLUTCH FAN
1. Measure the resistance between ground and the (K161) Clutch Fan Supply circuit at the Radiator Clutch Fan.

Is the resistance below 10k Ohms?

Yes

- Replace the Powertrain Control Module (PCM).
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace the Radiator Clutch Fan.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.