Circuit Test B - Main Power Relay
Enter this test only when directed here by other circuit tests. To prevent replacement of good components, check for faults in following components:
- Ignition switch.
- Alternator.
- Battery cables, ground straps and voltage regulator.
CIRCUIT PIN IDENTIFICATION (TEST B)
| Circuit | Breakout Box Pin No. | PCM Pin | Wire Color |
|---|---|---|---|
| GND | 4 | 4 | White/Green |
| GND | 10 | 10 | Black |
| GND | 19 | 19 | Black |
| GND | 43 | 43 | Black/Red |
| GND | 73 | 76 | Black |
| GND | 80 | 82 | Black |
| GND | 87 | 88 | Black |
| GND | 25 | 39 | Black/Red |
| VPWR | 51 | 56 | Black/White |
| VPWR | 57 | 61 | Black/White |
| VPWR | 81 | 83 | Black/White |
This circuit test is only intended to diagnose the following components and circuits:
- Harness circuits; VPWR and ground.
- Main power relay.
- Step 1) Check VPWR To PCM Turn ignition off. Install breakout box and connect PCM. Turn ignition on. Measure voltage between ground and breakout box test pins No. 51, 57 and 81. If voltage is less than 10 volts, go to next step. If voltage is greater than 10 volts, go to step 7). If sent here from switch monitor test and voltage is greater than 10 volts, go to CIRCUIT TEST QA.
- Step 2) Check VPWR Wire From Main Relay To PCM Turn ignition off. Install breakout box (leave PCM disconnected). Remove main power relay (located in engine compartment junction box). Measure resistance between Black/White wire at main power relay harness connector and breakout box test pins No. 51, 57 and 81. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair VPWR (Black/White) wire.
- Step 3) Check Battery Voltage At Main Power Relay Turn ignition off. Remove main power relay. Measure voltage at PWR terminal (Red wire) at main power relay connector. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, check 10-amp ENG CONT fuse. If fuse is not the problem, power distribution circuit.
- Step 4) Check PWR Circuit To Main Power Relay Turn ignition off. Remove main power relay (located in fuse panel). Turn ignition on. Measure voltage at PWR terminal (Red wire) and ground terminal (White/Green wire) at main power relay connector. If voltage is 10 volts or greater, go to step 6). If voltage is less than 10 volts, go to next step.
- Step 5) Check Ground At Main Power Relay Turn ignition off. Remove main power relay. Measure resistance between breakout box test pin No. 4 and GND (White Green wire) terminal at main power relay. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair GND circuit.
- Step 6) Test Main Relay Turn ignition off. Install breakout box (connect PCM). Disconnect main power relay. Apply battery power to main relay terminal No. 1 and ground terminal No. 2. With battery power applied, measure resistance between relay terminals No. 3 and 5. If resistance is less than 5 ohms with battery voltage applied, go to next step. If resistance is greater than 5 ohms with battery voltage applied, replace relay.
- Step 7) Check Grounds At PCM Leave ignition off. Install breakout box. (connect PCM). Measure resistance between ground and breakout box test pins No. 10, 19, 25, 43, 73, 80 and 87. If all resistance measurements are less than 5 ohms, ground circuits are okay, replace PCM. If any resistance measurement is greater than 5 ohms, repair GND circuit in question.