TEST 1 (Dwell Fixed Less Than 15 Degrees)
- Ground Violet and Black wire terminals of ALDL connector. See Fig 1
. With engine at part throttle, choke engine. If dwell does not change, go to step 2). If dwell increases, check for vacuum leak, exhaust leaks before O2 sensor, vacuum hose routing and EGR operation. If no leaks are present, repair carburetor.
- Disconnect O2 sensor. Connect digital voltmeter on 20-volt scale from battery positive terminal to ECM O2 sensor connector. Note dwell at part throttle. If dwell is less than 15 degrees, go to step 3). If dwell increases, check for open from ECM terminal No. 3 of C-45. See Fig 1
. If okay, replace O2 sensor.
- Stop engine, turn ignition on and measure voltage between ECM terminals No. 17 and 22. If less than 3 volts, go to step 4). If greater than 3 volts, check coolant sensor circuit.
- Check for open circuit from ECM terminal No. 20 to ground and check for grounded wire to ECM terminal No. 3 of C-45. If okay, check voltage from ECM terminal No. 5 to ground. See Figure
and Figure
.
- If voltage is less than 2 volts, go to step 6). If voltage is greater than 2 volts, check for open from ECM terminals No. 22 to TPS terminal "A." If okay, repair ECM connector or replace ECM.
- Check voltage at ECM terminal No. 7 of C-45. Voltage should be 5 volts. If not, replace ECM. If voltage is okay, check wiring between ECM terminal No. 5 and TPS terminal "B" and ECM terminal No. 7 and TPS terminal "C." If wiring is okay, adjust or replace TPS.
Courtesy of ISUZU MOTOR CO.