Ignition Relay Diagnosis

IGNITION RELAY DIAGNOSIS

CIRCUIT DESCRIPTION
The ignition relay, also called the EFI relay, provides ignition positive voltage to the control module and other engine control components anytime the ignition is ON. One side of the coil of the EFI relay is always grounded. The relay is energized when the ignition switch applies voltage to the other side of the coil. The switch side of the EFI relay receives power from the EFI fuse in the fuse block - underhood. When the coil is energized, a magnetic field closes the switch side of the relay, supplying power to the following engine components:
- Circuit opening relay, also called the fuel pump relay.
- Heated oxygen sensors (HO2S)
- Mass airflow (MAF) sensor
- Evaporative emission (EVAP) control system solenoids
- Idle air control (IAC) valve
- Powertrain control module (PCM)

DIAGNOSTIC AIDS
Check for any of the following conditions:
- Check the condition of the EFI relay circuits. Measure for continuity across the coil side terminals. Measure for infinite resistance across the switch side terminals while the relay is disconnected.
- The EFI relay electrical contacts may be pitted or sticking. Replace the EFI relay, if tapping gently on the relay, or wiggling the relay causes a change in the relay's operation.
- The performance of the EFI relay may be affected by temperature. Check the EFI relay after sitting outside overnight and after running the engine 30 minutes.
- If the EFI fuse opens during cranking, check for a shorted fuel pump/circuit. The EFI relay supplies current to the circuit opening relay that supplies power the fuel pump. The circuit opening relay is energized during cranking and when reference pulses are detected by the PCM.

An intermittent malfunction may be caused by a fault in the EFI relay electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions




Use the relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.

TEST DESCRIPTION

Steps 1 - 12:

Step 13:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
6. This step will verify the ground path for the EFI relay circuit.