For 1990-2009 cars

### Diagnostic Aids

• | This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test .

• | When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the mating electrical terminals for tightness.

• | Use the Using Connector Test Adapters for any test that requires probing the underhood fuse block terminals, component wire harness terminals or the ECM wire harness connector terminals.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

1. Ignition ON, clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Ignition ON, observe the DTC information with a scan tool.

### Circuit/System Testing

1. Ignition OFF, disconnect the EC ignition or main relay.

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the B+ supply circuit to the coil side of the main relay and the negative terminal of the battery.
3. Ignition ON, test for less than 0.1 volts between the B+ voltage circuit of the main relay and the positive battery terminal.

⇒ | If greater than 0.1 volts, repair the B+ voltage circuit to the coil side of the main relay for a short to ground or an open/high resistance.

Important: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the B+ voltage supply circuit to the switch side of the main relay and the negative terminal of the battery.
5. Ignition ON, test for less than 0.1 volts between the B+ voltage circuit of the main relay and the positive battery terminal.

⇒ | If greater than 0.1 volts, repair the B+ voltage circuit to the switch side of the main relay for a short to ground or an open/high resistance.

6. With the ignition OFF, connect a test lamp between the control circuit of the main relay and the B+ voltage supply circuit to the coil side of the main relay.
7. Turn ON the ignition. The test lamp should turn ON when the ignition switch is cycled ON and OFF when the ignition switch is cycled OFF.

⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit/connections test normal, replace the ECM.

⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.

Important: The ignition 1 voltage circuit is between the main relay and the ECM. The ignition 1 voltage is a feedback circuit.

8. Connect a 15A fusible link wire between the B+ supply voltage circuit and the ignition 1 voltage circuit of the main relay.
9. Attempt to start the engine. The engine should start.

⇒ | If the engine does not start, test the ignition 1 voltage circuit between the main relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the ECM.

10. If all circuits/connections test normal, test or replace the main relay.

### Component Testing

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the main relay.

⇒ | If the resistance is not within the specified range, replace the main relay.

2. Measure for infinite resistance between the following terminals of the main relay:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If continuity is detected, replace the main relay.

3. Connect a 20A fusible link wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒ | If the resistance measures more than 2 ohms, replace the main relay.

### Repair Instructions

Perform the Diagnostic Repair Verification

• | Relay Replacement

• | Engine Control Module Replacement for engine control module replacement, setup and programming.