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

POWER SUPPLY (MFI RELAY) AND IGNITION SWITCH-IG





INSPECTION
Using Scan Tool




HARNESS INSPECTION

STEP 1. Measure the ignition Switch-(IG) terminal input voltage.
- Engine control module connector: Disconnected

Voltage (V):
0 - 1 (Ignition switch: OFF)
Battery positive voltage (Ignition switch: ON)

OK: GO TO STEP 2
NG: Repair the harness. (82 - Ignition switch or inspect the ignition switch.)





STEP 2. Measure the power supply voltage of the MFI relay.
- Ignition switch: OFF
- MFI relay connector: Disconnected

Voltage (V): Battery positive voltage

OK: GO TO STEP 3
NG: Repair the harness. (A4 - Battery, A8 - Battery)





STEP 3. Check for an open circuit or a short-circuit to ground between the MFI relay and the engine control module.
- Engine control module connector: Disconnected
- MFI relay connector: Disconnected

OK: GO TO STEP 4
NG: Repair the harness. (A6 - 38)





STEP 4. Check for an open circuit or a short-circuit to ground between the MFI relay and the engine control module.
- MFI relay connector: Disconnected
- Engine control module connector: Disconnected

OK: GO TO STEP 5
NG: Repair the harnesses. (A2 - 12, A2 - 25)





STEP 5. Measure the power supply voltage of the actuator.
- MFI relay connector: Connected
- Engine control module connector: Connected

Voltage (V):
8 or higher (Engine: Cranking) Battery positive voltage (Engine: Racing)

OK: STOP
NG: MFI relay or engine control module is defective.




RELAY INSPECTION

Multiport Fuel Injection (MFI) Relay Check
1. Remove the MFI relay.





2. Check for continuity between the MFI relay terminals.





3. Use jumper wires to connect MFI relay terminal (7) to the positive battery terminal and terminal (5) to the negative battery terminal.

Caution
When connecting the jumper wires, be careful not to mistake the connection terminals, as damage to the relay will result.





4. Check the voltage at MFI relay terminal (1) while connecting and disconnecting the jumper wire at the negative battery terminal





5. Use the jumper wires to connect MFI relay terminal (8) to the positive battery terminal and terminal (6) to the negative battery terminal.





6. Check for continuity between MFI relay terminals (2)-(4) and terminals (3)-(4) while connecting and disconnecting the jumper wire at the negative battery terminal.
7. If there is an incorrect condition, replace the MFI relay.