GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Geo 🢒 1996 🢒 Metro 🢒 Engine 🢒 Engine Controls - 1.3L 🢒 Malfunction Indicator Lamp (MIL) Always On

Schematic Reference: Engine Controls Schematics

Circuit Description

The malfunction indicator lamp (MIL) is illuminated when the ignition is ON and the engine is OFF. Battery ignition voltage is supplied to the MIL. The PCM will turn the MIL ON by grounding the control circuit at the PCM. The MIL is normally OFF when the engine is running. A steady MIL with the engine running suggests a short to ground in the MIL control circuit or a DTC is set in the powertrain control system.

Diagnostic Aids

Check for any of the following conditions:

    • Check for a shorted MIL control circuit between the PCM and I/P Cluster Assembly.
    • A shorted I/P Cluster Assembly board may cause the MIL to stay ON.
    • Check for a faulty electrical connection to the PCM.

An intermittent malfunction may be caused by a fault in the MIL electrical circuit. Inspect the wiring harness and components for any of the following conditions:

    • Backed out terminals.
    • Improper mating of terminals.
    • Broken electrical connector locks.
    • Improperly formed or damaged terminals.
    • Faulty terminal to wire connections.
    • Physical damage to the wiring harness.
    • A broken wire inside the insulation.
    • Corrosion of electrical connections, splices, or terminals.

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.

  2. This step checks for a short to ground in MIL control circuit.

    3.

  3. This step checks for a short in the MIL control circuit between the PCM and the I/P cluster assembly.

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition, leaving the engine OFF.

Is the MIL ON?

--

Go to Step 3

Go to Step 5

3

  1. Check for a short to ground in the MIL control circuit between the PCM and the I/P Cluster Assembly.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 6

Go to Step 4

4
  1. Check the I/P Cluster Assembly for a shorted circuit board.
  2. Repair or replace as necessary.

Is the action complete?

--

Go to Step 6

--

5

Replace the PCM. Refer to Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 6

--

6

Start the engine and observe the MIL.

Does the MIL turn OFF in approximately 1 to 2 seconds after the engine is started?

--

System OK

Go to the Applicable Diagnostic Table