Inspection Procedure 28

INSPECTION PROCEDURE 28: Radiator Fan is Inoperative

Radiator Fan Circuit Part 1:

Radiator Fan Circuit Part 2:

CIRCUIT OPERATION
- The ECM sends a duty signal to the fan control module according to engine coolant temperature, vehicle speed, and the condition of the A/C switch. (The closer the average voltage at the terminal comes to five volts, the higher the fan speed becomes.)

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Malfunction of the fan motor relay.
- Malfunction of the fan motor.
- Malfunction of the fan control module.
- Improper connector contact, open or short-circuited harness wire.
- ECM failed.

DIAGNOSIS




STEP 1. Check connector C-121 at ECM for damage.

Q: Is the connector in good condition?

YES: Go to Step 2.

NO: Repair or replace it. Then confirm that the malfunction symptom is eliminated.

STEP 2. Check the output voltage at ECM harness side connector C-121.




1. Disconnect the connector C-121 and measure at the harness side.
2. Turn the ignition switch to the "ON" position.




3. Measure the voltage between terminal No. 18 and ground.
- Voltage should measure between 4.8 and 5.2 volts. (Fan rotates at high speed.)

4. Connect a jumper cable between terminal No. 18 and ground.
- The fan should stop.

5. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the voltage and fan condition normal?

YES: Replace the ECM. Then confirm that the malfunction symptom is eliminated.

NO: Go to Step 3.







STEP 3. Check for open circuit and short circuit to ground and harness damage between fan control module A-17 (terminal No. 2) and ECM connector C-121 (terminal No. 18).

NOTE: Check harness after checking intermediate connector A-13. If the intermediate connector is damaged, repair or replace it. Then confirm that the malfunction symptom is eliminated.

Q: Is the harness wire in good condition?

YES: Refer to, Engine Cooling Diagnosis - Symptom Chart in Cooling System/Testing and Inspection/Diagnosis By Symptom.

NO: Repair it. Then confirm that the malfunction symptom is eliminated.