Malfunction Indicator Lamp (MIL) Inoperative. Geo Tracker - 4WD 1997

For 1990-2009 cars

Refer to

#### Cell 20: Power and Ground

and

#### Cell 20: MIL and DLC

schematics.

### Circuit Description

There should always be a steady malfunction indicator lamp (MIL) when the ignition switch is in the ON position and the engine is not running. System voltage is applied to the indicator lamp when the ignition is ON and when the engine is running. The powertrain control module (PCM) controls the MIL and illuminates the lamp by providing a ground path through the MIL control circuit.

### Diagnostic Aids

Check for any of the following conditions:

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

• | With no MIL and the engine cranks but will not start, check for a faulty Main Relay.

• | With no scan tool data, no MIL, and the engine cranks but will not start, check for a shorted to ground 5 volt reference circuit (i.e. TP sensor, MAP sensor, fuel tank pressure sensor).

• | If the engine cranks but will not run, check for an open in the PCM ignition circuit or the battery feed circuit or for a faulty PCM to engine ground circuit.

An intermittent malfunction may be caused by a fault in an MIL control system 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. Checks the ground circuits to the PCM.

3. This step will verify whether the MIL circuit is at fault or if the PCM is not providing a ground path for the MIL circuit.

4. This step check whether ignition battery positive is being provided to the MIL circuit.

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

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 IG-COIL METER fuse. Was the IG-COIL METER fuse open? | -- | Go to Step 12 | Go to Step 3
3 | Attempt to start the engine. Does the engine start? | -- | Go to Step 6 | Go to Step 4

4

1. Disconnect the PCM electrical connector.
2. Using a test light connected to battery positive voltage, probe the PCM ground terminals (harness side).

Does the test light illuminate at each terminal?

--

Go to Engine Cranks but Does Not Run

Go to Step 5

5 | Repair the open in the PCM ground circuit(s) between the PCM and the G103 ground. Is the action complete? | -- | Go to Step 14 | --

6

1. Use a fused jumper wire that is connected to ground and backprobe the MIL control circuit, PPL/YEL wire, at the PCM electrical connector.
2. Turn ON the ignition, leaving the engine OFF.
3. Observe the MIL.

Does the MIL illuminate?

--

Go to Step 13

Go to Step 7

7

1. Turn ON the ignition, leaving the engine OFF.
2. Using a test light, backprobe the I/P cluster assembly connector terminal C3-11 (harness side).

Did test light illuminate?

--

Go to Step 8

Go to Step 9

8

1. Disconnect the I/P cluster assembly electrical connector C3.
2. Using a test light connected to battery positive voltage, probe terminal C3-3 of the I/P cluster assembly (harness side).
3. Turn the ignition switch to ON, and then turn the ignition switch to OFF while observing the test light.

Does the test light illuminate when the ignition switch is turned ON, and does the test light go OFF when the ignition switch is turned OFF?

--

Go to Step 11

Go to Step 10

9 | Repair the open in the BLK/WHT wire between the Junction Block and the I/P cluster assembly. Is the action complete? | -- | Go to Step 14 | --
10 | Locate and repair the open in the PPL/YEL wire between the I/P cluster assembly and the PCM. Is the action complete? | -- | Go to Step 14 | --

11

1. Check for any of the following conditions:

• | A faulty bulb

• | A faulty I/P circuit from connector C3 to the MIL bulb socket

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

2. Repair as necessary.

Is the action complete?

--

Go to Step 14

--

12 | Repair the short to ground in the IG-COIL METER fuse circuit. Is the action complete? | -- | Go to Step 14 | --
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 14 | --
14 | After repairs start the vehicle and observe the MIL. Did the MIL illuminate for approximately 3 seconds and then turn OFF? | -- | System OK | Go to the Applicable Table