Ignition Relay Diagnosis

Circuit Description
The IGN relay supplies a voltage to various fuses. The IGN relay is located in the underhood Electrical Center. The following components are powered by the IGN relay:
^ Injectors/Ignition coils
^ Throttle Actuator Control (TAC) module
^ Transmission
^ A/C system
^ [1][2]EVAP solenoid
^ MAF sensor
^ AIR pump and AIR solenoid relays
^ TCC/Cruise and Extended Travel brake switches

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter kit J 35616-A. Using this kit prevents damage to the harness/component terminals.

The following may cause an intermittent:
^ Poor connections.
^ Corrosion.
^ A mis-routed harness.
^ A rubbed through wire insulation.
^ A broken wire inside the insulation.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
4. This step tests the ignition relay ground circuit.
5. This step isolates the circuit from the IGN relay. All of the circuits at the relay are good if the test lamp illuminates.
11. Remove the underhood electrical center and inspect the circuits that are supplied a voltage by the IGN relay.