Ignition Relay: Testing and Inspection

IGNITION RELAY DIAGNOSIS

CIRCUIT DESCRIPTION
The ignition relay, also called the main relay, is controlled by the Powertrain Control Module (PCM). The PCM provides a ground for the relay's coil anytime the ignition switch is ON. The ignition relay supplies ignition positive voltage to many engine control Systems and components. The following components receive power from the main relay:
^ The fuel pump relay
^ The fuel injectors
^ The Mass Air Flow (MAF) sensor
^ The EVAP control system solenoids
^ The Exhaust Gas Recirculation (EGR) valve
^ The Idle Air Control (IAC) valve
^ The Powertrain Control Module (PCM)

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ Check the resistance of the ignition relay. The resistance across terminal 3 and terminal 5 is 79-95 ohms at 20°C (68°F). The resistance across terminal 1 and terminal 2 is infinite.
^ The ignition relay's electrical contacts may be pitted or sticking. Replace the ignition relay if tapping gently on the relay or wiggling the relay causes a change in the relay's operation.
^ The temperature may affect the performance of the ignition relay. Check the ignition relay after sitting outside overnight and after running the engine for 30 minutes.
^ Check for a faulty electrical connection to the PCM.

A fault in the ignition relay electrical circuit may cause an intermittent malfunction. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions




Use the above 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 1-4:

Steps 5-17:

The numbers below refer to the step numbers in the diagnostic table.
1. The Diagnostic System Check-Computers and Control Systems prompts the technician to complete some basic checks and to 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 whether the PCM is not providing a ground path for the ignition relay circuit. When terminal 2 of the ignition relay is grounded, the ignition relay turns ON.
9. This step checks for ignition positive voltage at the PCM. The PCM will not operate the ignition relay if there is no power to terminal C2-20.
11. This step checks for an open in the PCM electrical grounds. The PCM will not operate the ignition relay if there are no electrical grounds.