TEST 2 (Dwell Fixed Between 15-50 Degrees)

1. Start engine and ground Violet and Black wire terminals of ALDL connector. Run engine at part throttle for one minute and note dwell. Disconnect coolant temperature sensor and jumper connector terminals and again note dwell. See Fig 1 .
2. If dwell does not change, go to step 4). If dwell changes more than 5 degrees, check resistance of coolant sensor. If resistance is less than 1000 ohms, go to step 3). If resistance is greater than 1000 ohms, replace coolant sensor.
3. Reconnect coolant sensor and note dwell at part throttle. If dwell is fixed, go to step 4). If dwell is varying, connection was poor at coolant sensor.
4. Reconnect coolant sensor, return engine to idle. Disconnect O2 sensor and jumper ECM connector terminals. Note dwell change. If no dwell change, go to step 5). If dwell is less than 10 degrees, repair open in wires to O2 sensor.
5. Jumper ECM terminals No. 17 and 22. Note dwell change. If no dwell change, go to step 6). If dwell changes more than 5 degrees, repair open in wires to coolant sensor. Reconnect O2 sensor.
6. Check connection to ECM terminals No. 3, 17, 22 and 20. Check TPS adjustment. If no trouble found, replace ECM.

Fig 1: Wiring Diagram for TESTS 2 & 3

Courtesy of ISUZU MOTOR CO.