Table A1-1 No Malfunction Indicator Lamp (MIL)

Diagnostic Chart:

Wiring Diagram:

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 lamp when the ignition is ON and when the engine is running. The Powertrain Control Module (PCM) controls the MIL and illuminates the lamp by providing a ground path through the MIL control circuit.

Diagnostic Aids

An intermittent malfunction, may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Check for any of the following conditions:

^ Inspect the wiring harness electrical connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connections before component replacement.

^ If the engine runs OK, check for a faulty indicator bulb, or an open in the instrument cluster power circuit.

^ With no MIL and the engine cranks but will not start, check for a faulty Main Relay.

^ With no scan tool data, no MIL, and the engine cranks but will not start, check for a shorted to ground 5 volt reference circuit (i.e. Throttle Position (TP) Sensor, Manifold Absolute Pressure (MAP) Sensor, Idle Speed Control (ISC) Motor).

^ If the engine cranks but will not run, check for an open in the PCM ignition circuit or the battery feed circuit or for a poor PCM to engine ground circuit.

Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain OBD System Check 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.

2. A no MIL condition that is accompanied by a no start condition suggests a malfunctioning PCM ignition feed or battery feed circuit.

9. Use a test light to B+ in order to probe each of the PCM ground terminals to ensure that a good ground is present. Refer to PCM Terminal End View for terminal location of the PCM ground circuits.

18. Verifies the proper operation of the MIL.