System Diagnosis

Coolant Fan Does Not Turn On

1. Turn ignition switch to ON position, ground terminal B (WHT/BLK) of ALDL connector.
2. If coolant fan does not operate, go to step 3. If fan does operate, problem is ECM related.
3. Ensure terminal C1/21 (VIN K) or C3/E8 (VIN T) are grounded at ECM, disconnect fan relay connector, the measure voltage from coolant fan relay terminal 5 (BRN/WHT) and ground. If zero volts, check 650 (BRN/WHT) and 50 (BRN) wires and HTR-A/C fuse for open.
4. If battery voltage is present, ensure terminal C1/21 (VIN K) or C3/E8 (VIN T) are grounded at ECM, then measure voltage between coolant fan relay terminals 5 (BRN/WHT) and 2 (DK GRN/WHT). If zero volts, check 355 (DK GRN/WHT) wire for open.
5. If battery voltage is present, measure voltage from terminal 1 (RED) to ground. If zero volts, check 2 (RED) wire and fusible link C for open.
6. If battery voltage is present, disconnect coolant fan relay, then connect 20 amp fused jumper between terminals 1 (RED) and 4 (BLK/RED). If coolant fan runs, replace coolant fan.
7. If coolant fan does not operate, ensure fused jumper is connected as in step 6, disconnect coolant fan connector, then measure voltage between terminals B (BLK/RED) and ground. If zero volts, check 532 (BLK/RED) wire for open.
8. If battery voltage is present, ensure fused jumper is connected as in step 6, then measure voltage between terminals B (BLK/RED) and A (BLK). If zero volts, check 150 (BLK) wire for open.
9. If battery voltage is present, replace coolant fan motor.

Coolant Fan Does Not Turn Off W/Engine Coolant Cool, A/C Mode Selector Off & Ignition Switch In Run

1. Turn ignition switch to RUN position, disconnect coolant fan relay, then connect test lamp between coolant fan relay terminals 5 (BRN/WHT) and 2 (DK GRN/WHT). If test lamp does not light, replace coolant fan relay.
2. If test lamp lights, check 335 (DK GRN/WHT) wire for short to ground. If wire is shorted, repair or replace as needed.
3. If wire is good, problem is ECM related.