Malfunction Indicator Lamp (MIL) Inoperative. Chevrolet Metro 2000

For 1990-2009 cars

Refer to

#### Cell 21: MIL and DLC

and to

#### Cell 21: Power and Ground

.

### Circuit Description

The malfunction indicator lamp (MIL) illuminates when the ignition is ON, and the engine is OFF. Battery ignition voltage is supplied to the MIL. The powertrain control module will turn the MIL ON by grounding the lamp control circuit. Under normal conditions, the MIL is OFF when the engine is running.

### Diagnostic Aids

Inspect for any of the following conditions:

• | If the engine starts and runs OK, look for a faulty indicator bulb or for an open in the instrument cluster power circuit

• | If the MIL is not illuminated and the engine cranks but will not start, inspect for a faulty main relay.

• | If there is not any scan tool data, an illuminated MIL, and the engine cranks but will not start, check for a 5 volt reference circuit shorted to ground.

• | Inspect for a faulty electrical connection to the PCM.

A fault in the MIL electrical circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:

• | Backed out terminals.

• | Incorrect mating of terminals.

• | Broken electrical connector locks.

• | Incorrectly formed terminals or damaged terminals.

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, of splices, or of 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 to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.

2. This step will verify if the MIL circuit is faulty, or if the PCM is not providing a ground path for the MIL circuit.

3. This step will verify the condition of the MIL control circuit. The PCM is providing the ground for the test light.

4. This step checks for an open in the ignition positive voltage circuits from the main relay. There is not any MIL control or any serial data with an open circuit between the last two splices before the PCM.The engine may start and run.

5. This step checks for a short to ground in the PCM 5 volt reference circuit. If the reference voltage circuit is shorted to ground, the MIL will not operate, and the engine will not start. Check the circuit wiring, the sensors, and the components for shorts to ground on the 5 volt reference circuit.

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

Check for an open in the following fuses:

• | The IG-COIL fuse

• | The FI fuse

Was an open fuse found?

--

Go to Step 20

Go to Step 3

3 | Attempt to start the engine. Does the engine start? | -- | Go to Step 4 | Go to Step 10
4 | Install a scan tool, and select the data display. Does the scan tool display any data? | -- | Go to Step 5 | Go to Step 10

5

1. Disconnect the PCM electrical connector C1.
2. Back out the PCM terminal C1-17.
3. Jump the C1-17 circuit to ground using a fused jumper wire.
4. Turn ON the ignition, leaving the engine OFF.
5. Observe the MIL.

Does the MIL illuminate?

--

Go to Step 18

Go to Step 6

6

1. Turn ON the ignition, leaving the engine OFF.
2. Backprobe terminal C1-2 on the harness side of the instrument panel (IP) cluster assembly connector, using a test lamp that is connected to ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 8

7

1. Disconnect the IP cluster assembly electrical connector C1.
2. Probe terminal C1-4 on the harness side of the IP cluster assembly connector, using a test lamp that is connected to battery positive voltage.
3. Turn the ignition switch ON then OFF while observing the test lamp.

Does the test lamp illuminate if the ignition switch is turned ON and turn OFF if the ignition switch is turned OFF?

--

Go to Step 19

Go to Step 9

8 | Repair the open in the circuit between terminal C4-3 of the junction block and terminal C1-2 of the IP cluster assembly connector. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | --
9 | Locate and repair the open in the MIL control circuit between the instrument panel cluster assembly and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | --

10

1. Turn ON the ignition, leaving the engine OFF.
2. Backprobe terminals C1- and C1- 15 in the PCM electrical connector, with a test lamp that is connected to ground.

Does the test light illuminate at each terminal?

--

Go to Step 11

Go to Step 13

11 | Backprobe terminal C3-20 in the PCM electrical connector with a test lamp that is connected to ground. Does the test light illuminate? | -- | Go to Step 14 | Go to Step 12
12 | Repair the open in the ignition positive voltage circuit between the IG-COIL fuse and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | --

13

1. Check for an open in the ignition positive voltage circuit between the main relay and the PCM.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 21

Go to Main Relay Circuit Diagnosis

14

1. Turn ON the ignition, leaving the engine OFF.
2. Backprobe the PCM reference voltage terminal C2-1 to ground with a DMM.

Was the measured voltage at the specified value?

5 V

Go to Step 18

Go to Step 15

15

1. Check for a short to ground in the reference voltage circuit and in the circuit components.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 21

Go to Step 16

16

1. Disconnect the PCM connector terminal C1.
2. Probe the harness side of the PCM ground terminals with a test lamp connected to battery positive voltage.

Does the test light illuminate at each terminal?

--

Go to Step 18

Go to Step 17

17 | Repair the open in the PCM ground circuits between the PCM and the G104 ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | --
18 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 21 | --

19

1. Check for any of the following conditions:

• | A faulty bulb

• | A faulty instrument panel (IP) circuit from connector C1 to the MIL bulb socket

• | A faulty electrical connection in the I/P cluster assembly

2. Repair as necessary.

Is the action complete?

--

Go to Step 21

--

20 | Repair the short to ground in the IG-COIL fuse or in the FI fuse circuits. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | --

21

1. Turn ON the ignition, leaving the engine OFF.
2. Observe the MIL.
3. Start the engine, and continue to observe the MIL.

Did the MIL illuminate if the ignition was ON, and OFF after the engine was started?

--

System OK

Go to the applicable diagnostic table