Main Relay (Computer/Fuel System): Testing and Inspection

Fig. 17 Relay Terminals:

Fig. 18 Relay Terminals:

To perform a complete test of the fuel pump, ASD or oxygen sensor heater relay, or its circuitry, refer to the DRB scan tool and the appropriate Powertrain Diagnostic. To test the relay only, refer to the following: The terminals on bottom of each relay are numbered or.

OPERATION
- Terminal number 30 is connected to battery voltage. For both the ASD and fuel pump relays, terminal 30 is connected to battery voltage at all times.
- The PCM grounds coil side of relay through terminal number 85.
- Terminal number 86 supplies voltage to Coil side of relay.
- When the PCM de-energizes the relay, terminal number 87A connects to terminal 30. This is the OFF position. In the OFF position, voltage is not supplied to rest of circuit. Terminal 87A is the center terminal on relay.
- When the PCM energizes the ASD and fuel pump relays, terminal 87 connects to terminal 30. This is the ON position. Terminal 87 supplies voltage to rest of circuit.

TESTING
The following procedure applies only to ASD, oxygen sensor heater and fuel pump relays.
1. Remove relay from PDC connector before testing.
2. With relay removed from vehicle, use an ohmmeter to check resistance between terminals 85 and 86. The resistance should be between 75 ± 5 ohms.
3. Connect ohmmeter between terminals 30 and 87A. Ohmmeter should show continuity between terminals 30 and 87A.
4. Connect ohmmeter between terminals 87 and 30. Ohmmeter should not show continuity at this time.
5. Connect one end of a jumper wire (16 gauge or smaller) to relay terminal 85. Connect other end of jumper wire to ground side of a 12 volt power source.
6. Connect one end of another jumper wire (16 gauge or smaller) to power side of 12 volt power source. Do not attach other end of jumper wire to relay at this time.

WARNING: DO NOT ALLOW OHMMETER TO CONTACT TERMINALS 85 OR 86 DURING THIS TEST.

7. Attach other end of jumper wire to relay terminal 86. This activates relay. The ohmmeter should now show continuity between relay terminals 87 and 30. Ohmmeter should not show continuity between relay terminals 87A and 30.
8. Disconnect jumper wires.
9. Replace relay if it did not pass continuity and resistance tests. If relay passed tests, it operates properly. Check remainder of relay circuits using DRB scan tool. Also refer to Wiring Diagrams.