Malfunction Indicator Lamp (MIL) Inoperative

EFI Relay Circuit:

Circuit Description

There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition switch is in the ON position and the engine is not running. System voltage is applied to the indicator bulb. The Powertrain Control Module (PCM) will control the MIL and turn it ON by providing a path to ground.

Diagnostic Aids

Check Electronic Fuel Injection (EFI), IGN and GAUGE fuses for opens and make sure EFI Relay is securely mounted into the fuse and relay box.

If the EFI fuse opens (blows) during cranking, check for a shorted fuel pump/circuit. The EFI relay supplies power to the circuit opening relay which in-turn powers the fuel pump. The circuit opening relay is energized during cranking and when reference pulses are monitored by the PCM.

An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.

Use the following 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

The numbers below refer to the step numbers in the Diagnostic Table.

3. If other Instrument Cluster Assembly (ICA) functions are not working correctly check for an open GAUGE fuse or for a lack of power and ground to the ICA.
4. This step checks for an open MIL Control circuit or for an internal PCM failure.
5. If the MIL does NOT illuminate when jumpered to ground, the failure is internal to the ICA.
10. This step checks for an open EFI Relay.
12. This step checks for open PCM ground circuits.
13. A shorted sensor reference voltage circuit may cause a no start and no MIL condition.