Malfunction Indicator Lamp (MIL) Inoperative. Chevrolet Alero Export 1999

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Alero Export 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 Malfunction Indicator Lamp (MIL) Inoperative

Engine Controls Components
Cell 23: Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views With EGR
Handling ESD Sensitive Parts Notice
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 positive voltage #2 fuse will cause the following conditions:

•	Entire cluster to be inoperative

•	May set DTC U1000

•	Cause a no start

Check the battery positive voltage and ignition positive voltage #2 circuits for poor electrical connections if the MIL is intermittent. It takes very little resistance in the battery positive voltage and the ignition positive voltage #2 circuits to cause an intermittent condition.

Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following conditions:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminals to wiring connections

•	Physical damage to 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.

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

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

•	Open PCM ignition positive voltage #2 circuit

•	Open battery positive voltage circuit

•	Poor ground at the engine block

•	Malfunctioning PCM

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

It takes very little resistance for the battery positive voltage and the ignition positive voltage #2 circuits to cause an intermittent condition. The battery positive voltage and the ignition positive voltage #2 circuits should also be checked for a poor electrical connection as described in diagnostic aids.

Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline information for PCM programming and Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Learn Procedure.

Before replacing the PCM, check for the following condition(s):

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminals to wiring connections

•	Physical damaged to the wiring harness

A shorted MIL circuit can be diagnosed with a scan tool. Refer to Powertrain Control Module Outputs Diagnosis .

An open MIL circuit can be diagnosed with a scan tool. Refer to Powertrain Control Module Outputs Diagnosis .

The PCM grounds will only cause a problem if all of the grounds are not making a good connection. If the PCM ground problem is suspected, the most probable place to check is where all of the grounds meet, at the engine block. Connections that are suspected of malfunctioning should be thoroughly checked as described in the diagnostic aids.

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

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 switch leaving the engine OFF.

Is the MIL ON?

Go to Step 3

Go to Step 4

Check for a poor electrical connection(s) in the following circuits:

•	Battery positive voltage circuit

•	Ignition positive voltage #2 circuit

Repair the circuit(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 22

Go to Step 5

Attempt to start the engine.

Does the engine start?

Go to Step 6

Go to Step 7

Check for a poor PCM ground connection(s) at the following locations:

•	Engine block

•	PCM electrical terminal connection(s)

Repair the connection(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 22

Turn OFF the ignition switch.
Disconnect the PCM electrical connectors from the PCM.
Turn ON the ignition switch leaving the engine OFF.
Connect a test light to ground.
Probe the MIL driver circuit (wiring harness side).

Does the MIL illuminate ON the IPC?

Go to Step 8

Go to Step 9

Inspect the following fuses:

•	Battery positive voltage

•	Ignition positive voltage #2

Replace any open fuse.

Are the fuses OK?

Go to Step 10

Go to Step 11

Check for poor electrical terminal connection(s) at the PCM electrical connector(s) in the following circuit(s):

•	Battery positive voltage

•	Ignition positive voltage #2

•	MIL control circuit

Repair the electrical connection(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 22

Go to Step 12

Did the test light illuminate?

Go to Step 13

Go to Step 14

Turn OFF the ignition switch.
Disconnect the PCM electrical connectors from the PCM.
Turn ON the ignition switch leaving the engine OFF.
Connect a test light to ground.
Probe the ignition positive voltage #2 circuit (wiring harness side).

Does the test light illuminate?

Go to Step 15

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 22

Turn OFF the ignition switch.
Check for poor electrical terminal connection(s) at the PCM.
If terminal connections are OK , then replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

Go to Step 22

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

Is the action complete?

Go to Step 22

Check for the following condition(s) in the MIL control circuit.

•	Open circuit

•	Poor electrical terminal connection

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

Was a repair necessary?

Go to Step 22

Go to Step 17

Connect a test light to ground.
Probe the PCM battery feed terminal.

Does the test light illuminate?

Go to Step 18

Go to Step 19

Repair the open ignition positive voltage #2 circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 22

Check for an open in the following circuit(s):

•	Ignition positive voltage #2

•	Battery positive voltage

Repair the circuit(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 22

Go to Step 20

Check for a poor electrical terminal connection(s) at the PCM electrical connector(s) in the following circuit(s):

•	Battery positive voltage

•	Ignition positive voltage #2

Repair the electrical connection(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 22

Go to Step 21

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

Is the action complete?

Go to Step 22

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

Is the action complete?

Go to Step 22

Check for a poor PCM ground connection(s) at the following locations:

•	Engine block

•	PCM electrical terminal connection

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

Was a repair necessary?

Go to Step 22

Go to Step 12

Start the engine.
Idle the engine until the normal operating temperature is reached.
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