Malfunction Indicator Lamp (MIL) Inoperative. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Sonoma Pickup - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L (L43) 🢒 Malfunction Indicator Lamp (MIL) Inoperative

Engine Controls Components
MIL, Generator, and Fuel Composition Sensor
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

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

Diagnostic Aids

An open ignition fuse causes the MIL to be inoperative.

Check any circuitry that is suspected of causing an intermittent problem for the following conditions:

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Physical damage to the wiring harness

Test Description

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

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 captured when the malfunction occurred. The scan tool stores this data for later reference.

If no malfunctions are present at this point and no DTCs were set, refer to Diagnostic Aids for additional checks and information.

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

•	Open ECM B fuse

•	Open ECM 1 fuse

•	Poor ground at the engine block

•	Malfunctioning PCM

Program the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline information for PCM programming.

Step

Action

Values

Yes

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

Go to Step 2

Go to

Powertrain On Board Diagnostic (OBD) System Check

Turn ON the ignition, with the engine OFF.

Is the MIL ON?

Go to Diagnostic Aids

Go to Step 3

Attempt to start the engine.

Does the engine start?

Go to Step 4

Go to Step 6

Check the gauges fuse in the instrument panel fuse block for an open.

Is the fuse open?

Go to Step 14

Go to Step 5

Turn OFF the ignition.
Disconnect the PCM harness connectors from the PCM.
Turn ON the ignition, with the engine OFF.
Connect a test lamp to ground.
Probe the MIL control circuit.

Is the test lamp ON?

Go to Step 7

Go to Step 12

Inspect the following fuses:

•

ECM B

•

ECM 1

Replace any open fuse.

Is a fuse open?

Go to Step 9

Go to Step 8

Remove the gauges fuse.
Connect a test lamp to ground
Turn the ignition ON.
Probe the MIL control circuit at the PCM connector.

Is the test lamp ON?

Go to Step 11

Go to Step 10

Turn OFF the ignition.
Disconnect the PCM C1 connector from the PCM.
Turn ON the ignition, with the engine OFF.
Connect a test lamp to ground.
Probe the B+ input from the ECM 1 fuse at the PCM connector.

Is the test lamp ON?

Go to Step 13

Go to Step 16

Check for a short to ground in the circuit of the fuse that was open.
Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems.
Replace the open fuse.

Is the action complete?

Go to Step 19

Turn OFF the ignition.

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

Go to Step 19

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

Is the action complete?

Go to Step 19

Remove the instrument cluster from the dash panel. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.
Check for the following conditions in the MIL control circuit:

•

Open

•	Poor connection

Repair circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 19

Go to Step 15

Connect a test lamp to ground.
Turn the ignition key to the ON position.
Probe the B+ input from the ECM 1 fuse at the PCM C1 connector.

Is the test lamp ON?

Go to Step 10

Go to Step 18

Repair the short to ground between the gauges fuse and the instrument cluster. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 19

Check for an open in the following :

•	B+ supply from gauges fuse at the instrument cluster

•	Instrument cluster connector terminals

•	Defective bulb

Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 19

Go to Step 17

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

Is the action complete?

Go to Step 19

Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Is the action complete?

Go to Step 19

Repair the open in the B+ circuit from the ECM B fuse and the PCM.

Is the action complete?

Go to Step 19

Go to Step 12

Turn ON the ignition with the engine OFF and make sure the MIL is ON.
Start the engine and make sure the MIL turns OFF after the engine has started.
Check to see if any DTCs are set.

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

Go to applicable DTC table

System OK