Power Transistor - Test Procedure Correction
89isuzu08BULLETIN NUMBER SB89-03-001
ISSUE DATE October 5, 1989
GROUP EMISSIONS
POWER TRANSISTOR TEST PROCEDURE (4ZE1 ENGINE) (WORKSHOP MANUAL CORRECTION)
VEHICLES AFFECTED
All Isuzu models with 4ZE1 engine.
SERVICE INFORMATION
The power transistor test procedure is incorrectly described in the following Workshop Manuals:
Manual Page No.
1988 Trooper II (KT) 03-48
(Publication No. ARM-SVC-157, part No. 2-90988-032-0)
1989 Trooper II (KT) 03-77
(Publication No. AING-SVC-177, part No. 2-90989-032-0)
1988/89 Pickup (TF) 6E1-82
(Publication No. AINU-SVC-175, part No. 2-90989-022-0)
This Service Bulletin contains the correct testing procedure for the power transistor.
TEST AT INTERMEDIATE CONNECTOR
For ease of procedure, testing of the power transistor may be done at intermediate connector H14, a 16- pin black connector located next to the battery. If the transistor fails the test at the intermediate connector, you must repeat the test at the transistor itself. If the transistor now tests good, there is a fault in the wiring between the transistor and the intermediate connector.
1. Disconnect the high-tension cable between the ignition coil and the distributor at the distributor side.
2. Attach a spark test tool (Kent-Moore J-125 or equivalent) to the end of the high tension cable from the coil. If a spark test tool is not available, hold the end of the disconnected high tension cable approximately 5-6 mm (1/4 in.) away from a metal surface with a pair of insulated pliers.
3. Turn the ignition switch to "ON".
4. Connect the positive end of a "D" size 1.5 volt battery to pin # 4 (on TF models) or pin # 72 (on KT models) of connector H14 on the transistor side of the connector. Connect the negative end of the battery to ground.
5. As you connect and disconnect the battery from ground, a spark should jump across the gap in the spark tool or the air gap between the high tension cable and ground. Repeat this step several times.
If spark does not occur, perform the test at the power transistor:
TEST AT POWER TRANSISTOR
1. Disconnect the high-tension cable between the ignition coil and the distributor at the distributor side.
2. Attach a spark test tool (Kent-Moore J-125 or equivalent) to the end of the high-tension cable from the coil. If a spark test tool is not available, hold the end of the disconnected high tension cable approximately 5-6 mm (1/4 in.) away from a metal surface with a pair of insulated pliers.
3. Using a jack or lift, elevate the right front side of the vehicle. Support the vehicle with a jack stand.
4. Remove the right front tire.
5. Unsnap the rubber cover on the inner fender.
6. Remove the power transistor from the bottom of the intake manifold.
7. Disconnect the power transistor harness at the connector.
8. Connect a jumper lead from the harness side connector (terminal 71 on KT models; terminal 1 on TF models) to the power transistor connector (terminal 71 on KT models; terminal 1 on TF models).
9. Connect a second jumper lead from the power transistor connector (terminal 72 on KT models; terminal 2 on TF models) to the negative (-) side of a 1.5V dry cell battery.
10. Connect a third jumper lead from the harness side connector (terminal 72 on KT models; terminal 2 on TF models) to the positive (+) side of the dry cell battery.
11. Ground the power transistor to the vehicle frame.
12. Turn the ignition switch to the "ON" position.
13. Disconnect and reconnect the jumper lead at the power transistor connector. Verify that a spark occurs across the gap in the spark tool or the air gap between the high tension cable and ground. Repeat this step several times.
If spark does not occur, replace the power transistor together with the bracket.
If spark occurs during testing at the intermediate connector and at the power transistor (the power transistor is found to be normal), then check its wiring circuitry as follows:
Power Transistor Circuitry Test
1. Check for voltage at the ignition coil.
- If no voltage, check for voltage at Fuse 14.
- If there is voltage, check for power from the ignition switch to Fuse 14.
2. Check for voltage between the power transistor and the ignition coil.
3. Using an ohmmeter, check the circuit from the power transistor to the ECM N5 connector, pin # 1.
RESULT: Continuity
4. Measure the same circuit to ground.
RESULT: NO Continuity
5. If a problem is found, correct or replace the defective part.