GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Cavalier 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 Malfunction Indicator Lamp (MIL) Inoperative

Object Number: 639711 Size: LF
Engine Controls Components
Power, Ground, BCM, and DLC
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

When the ignition is turned ON, the malfunction indicator lamp (MIL) will momentarily flash ON then OFF and remain ON until the engine is running, if no diagnostic trouble codes (DTCs) are stored. The powertrain control module (PCM) controls the MIL by providing a ground path through the MIL control circuit to turn ON the MIL.

Diagnostic Aids

An open ignition fuse will cause the entire cluster to be inoperative, and may set DTCs P1629 and U1016.

Inspect the battery and the ignition positive voltage circuits for faulty connections if the MIL is intermittent.

Any circuitry that is suspected of causing an intermittent complaint should be thoroughly inspected for:

    • Backed-out terminals
    • Improper mating
    • Broken locks
    • Improperly formed or damaged terminals
    • Faulty terminal-to-wiring connections
    • Physical damage to the wiring harness

Test Description

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

  1. The Powertrain (OBD) System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool, if applicable. This creates an electronic copy of the data that was captured when the malfunction occurred. The scan tool stores this data for later reference.

    2.

  2. Connections that are suspected of malfunctioning should be thoroughly inspected as described in the diagnostic aids.

    3.

  3. If the engine fails to start and the MIL is inoperative, then the malfunction can be isolated to one of the following items:

    4. • An open PCM ignition positive voltage circuit
    • An open battery positive voltage circuit
    • A faulty ground at the engine block
    • A malfunctioning PCM

  4. Probing the MIL circuit with a test lamp to a ground simulates the PCM's control of the MIL. If the MIL illuminates, then the malfunction can be isolated to the control of the MIL or to a faulty electrical connection at the MIL terminal to the PCM. Electrical connections that are suspected of malfunctioning should be thoroughly inspected as described in the diagnostic aids.

    5.

  5. It takes very little resistance for the battery and the ignition 1 feed circuits to cause an intermittent condition. The battery and the ignition 1 feed circuits should also be inspected for electrical connections as described in diagnostic aids.

    6.

  6. A shorted MIL circuit can be diagnosed with a scan tool.

    7.

  7. An open MIL circuit can be diagnosed with a scan tool.

    8.

  8. For instrument panel control (IPC) replacement procedures, refer to Instrument Panel, Gauges, and Console in Body and Accessories.

    9.

  9. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline™ information for PCM programming.

    10.

  10. If no malfunctions are present at this point and no DTCs were set, refer to the diagnostic aids for additional checks and information.

No Malfunction Lamp (MIL) Check Engine

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

Turn ON the ignition, with the engine OFF.

Is the MIL ON?

--

Go to Step 3

Go to Step 4

3

  1. Inspect for a faulty electrical connections in the following circuits:
    2. • The battery feed circuit
    • The ignition feed circuit
  2. Repair the circuits as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 19

Go to Diagnostic Aids

4

Attempt to start the engine.

Does the engine start?

--

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connectors from the PCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp to ground.
  5. Probe the MIL driver circuit and observe the MIL.

Does the MIL illuminate?

--

Go to Step 7

Go to Step 8

6

Inspect the following fuses:

    • The battery feed
    • The ignition feed

Are the fuses OK?

--

Go to Step 9

Go to Step 10

7

  1. Inspect for faulty electrical connections at the PCM.
  2. Repair the electrical connections as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 19

Go to Step 18

8

Did the test lamp illuminate?

--

Go to Step 11

Go to Step 12

9
  1. Turn OFF the ignition.
  2. Disconnect the PCM electrical connectors from the PCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp to a ground.
  5. Probe the ignition positive voltage circuit.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 14

10
  1. Check for a short to ground in the circuit of the fuse that was open.
  2. Repair the circuit as necessary. Refer to Connector Repairs .
  3. Replace the open fuse.

Is the action complete?

--

Go to Step 19

--

11

Repair the short to voltage in the MIL control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 19

--

12

  1. Inspect for the following conditions in the MIL control circuit:
    2. • An open circuit
    • A faulty electrical terminal connection
  2. Repair the circuit as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 19

Go to Step 18

13
  1. Connect a test lamp to a ground.
  2. Probe the PCM battery positive voltage terminal.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 16

14

Repair the open in the ignition positive voltage feed circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 19

--

15
  1. Check for faulty electrical connections in the following circuits:
    2. • The battery positive voltage
    • The ignition positive voltage
  2. Repair the electrical connections as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 19

Go to Step 18

16

Repair the open in the PCM battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 19

--

17

Replace the instrument panel console (IPC). Refer to Instrument Cluster Replacement in Instrument Panel, Gauges, and Console.

Is the action complete?

--

Go to Step 19

--

18

Important: Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 19

--

19

  1. Idle the engine until the normal operating temperature is reached.
  2. Check to see if any DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to the applicable DTC table

System OK