Transmission Oil Cooling Fan Inoperative
NOTE:
Transmission Control Module (TCM) monitors transmission oil cooling fan, cooling fan circuit and cooling fan relay and will store a Diagnostic Trouble Code (DTC) if a fault is detected. To diagnose an inoperative transmission oil cooling fan, a DRB scan tool, volt/ohm meter and vehicle wiring diagrams are required. If DTC P1738 is present, see appropriate DIAGNOSIS article in TRANSAXLES/TRANSMISSIONS to retrieve DTCs and for detailed testing procedures.
- Ensure all diagnostic trouble codes are repaired BEFORE diagnosing this symptom. If radiator and transmission oil cooling fans operate continuously, go to step 5 . If radiator and transmission oil cooling fans do not operate continuously, go to next step.
- If transmission oil cooling fan operates continuously, go to step 6 . If transmission oil cooling fan does not operate continuously, go to next step.
- Using DRB scan tool, activate low speed radiator fan relay. If radiator cooling fan operates, go to next step. If radiator cooling fan does not operate, diagnose and repair radiator cooling fan circuit. See RADIATOR COOLING FAN INOPERATIVE .
- If transmission oil cooling fan does not operate when radiator cooling fan operates, go to step 7 . If transmission oil cooling fan operates when radiator cooling fan operates, system is operating properly at this time. Check for an intermittent condition.
- Turn ignition off. Locate power distribution center and remove low speed radiator fan relay. If radiator and transmission oil cooling fans stop operating, replace low speed radiator fan relay. If radiator and transmission oil cooling fans do not stop operating, repair short to voltage in Dark Green wire. See WIRING DIAGRAMS .
- Turn ignition off. Locate power distribution center and remove transmission fan relay. If transmission oil cooling fan continues to operate, repair short to voltage in Dark Blue wire. See WIRING DIAGRAMS . If transmission oil cooling fan stops operating, replace transmission oil cooling fan motor.
- Stop actuation of low speed radiator fan relay. Turn ignition off. Locate power distribution center and remove transmission fan relay. Using a DVOM connected to ground, measure voltage at relay cavity No. 36 (Red/Gray wire). See Figure . If voltage reading is more than 10 volts, go to next step. If voltage reading is not more than 10 volts, repair open in power feed circuit (Red/Gray wire). See WIRING DIAGRAMS .
- Using DRB scan tool, activate low speed radiator fan relay. Using a DVOM connected to ground, measure voltage at transmission fan relay cavity No. 10 (Dark Green wire). See Figure . If voltage reading fluctuates between zero and more than 10 volts, go to next step. If voltage reading does not fluctuate between zero and more than 10 volts, repair open in low speed radiator fan relay output circuit (Dark Green wire). See WIRING DIAGRAMS .
- Stop actuation of low speed radiator fan relay. Turn ignition off. Using a DVOM connected to ground, measure resistance at transmission fan relay cavity No. 12 (Black wire). See Figure . If resistance reading is less than 5 ohms, go to next step. If resistance reading is not less than 5 ohms, repair open ground circuit (Black wire). See WIRING DIAGRAMS .
- Turn ignition off. Using a jumper wire, jumper across relay cavities No. 36 (Red/Gray wire) and No. 28 (Dark Blue wire). See Figure . If transmission oil cooling fan operates, replace transmission fan relay. If transmission oil cooling fan does not operate, go to next step.
- With jumper wire still connected between relay cavities No. 36 (Red/Gray wire) and No. 28 (Dark Blue wire), disconnect 2-pin transmission oil cooling fan harness connector. Using a DVOM connected to ground, measure voltage at terminal No. 1 (Dark Blue wire) of 2-pin transmission oil cooling fan harness connector. See Fig 1 . If voltage reading is less than 10 volts, repair open in Dark Blue wire between power distribution center and transmission oil cooling fan. See WIRING DIAGRAMS . If voltage reading is not less than 10 volts, go to next step.
- Remove jumper wire. Using a DVOM connected to ground, measure resistance at 2-pin transmission oil cooling fan harness connector terminal No. 2 (Black wire). See Fig 1 . If resistance is less than 5 ohms, replace transmission oil cooling fan. If resistance is not less than 5 ohms, repair open in transmission oil cooling fan ground circuit (Black wire). See WIRING DIAGRAMS .