Malfunction Indicator Lamp Circuit Check. Chevrolet Cavalier (CNG) 1998

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1998 🢒 Cavalier (CNG) 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Malfunction Indicator Lamp Circuit Check

Handling Electrostatic Discharge Sensitive Parts Notice
Handling Electrostatic Discharge Sensitive Parts Notice
Handling Electrostatic Discharge Sensitive Parts Notice
Engine Controls Components
Power, Ground, MIL and DLC
OBDII Symbol Description Notice

Circuit Description

The MIL will illuminate at key ON and stay on until the engine is started. When the engine is running and no diagnostic trouble codes (DTCs) are stored, the powertrain control module (PCM) turns off the MIL. The ignition switch supplies battery voltage directly to the MIL telltale. The PCM controls the MIL, providing a ground path through the MIL control circuit in order to turn ON the MIL. The MIL control circuit is routed through the alternative fuel (AF) electronic control unit (ECU) to allow the ECU to turn ON the MIL if an AF system DTC is set.

Diagnostic Aids

An open Ignition #1 fuse will cause the entire IP cluster to be inoperative. A missing or disconnected AF ECU will cause the MIL to be inoperative.

Inspect any circuitry that is suspected of causing an intermittent complaint for the following conditions:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal wiring connections

•	Physical damage to the wiring harness

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

The AF Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data with the scan tool if applicable. This creates an electronic copy of the data when the fault occurred. The information is then stored in the scan tool for later reference.

If the engine fails to start and the MIL is inoperative, then the fault can be isolated to either the PCM ignition feed fuses (PCM/IGN or CLS/PCM), the battery feed fuse (PCM), a poor PCM ground at the engine block or the PCM.

An MIL that responds correctly to the scan tool commands indicates that the fault is not present at this time or that the condition has been corrected.

This step isolates a PCM problem from a circuit problem.

Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.

For IPC replacement procedures, refer to IP Cluster Replacement in Instrument Panel, Gauges and Console in the J Platform Service Manual.

PCM grounds will cause a problem if all the grounds do make a good connection. If a PCM ground problem is suspected, inspect all the grounds at the engine block.

Step

Action

Value(s)

Yes

Was the AF Powertrain OBD System Check performed?

Go to Step 2

Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check

Turn OFF the engine for 15 seconds.
Turn ON the ignition with the engine OFF.

Is the MIL ON?

Go to Step 4

Go to Step 3

Attempt to start the engine.

Does the engine start?

Go to Step 6

Go to Step 7

Install a scan tool.
Command the MIL ON and OFF.

Does the MIL turn ON and OFF when commanded?

Go to Step 32

Go to Step 5

Turn OFF the ignition.
Disconnect the BLK PCM connector.
Turn ON the ignition.

Is the MIL ON?

Go to Step 18

Go to Step 28

Turn OFF the ignition.
Disconnect the BLK PCM connector.
Turn ON the ignition.
Probe the MIL control circuit with a fused jumper connected to the ground.

Is the MIL ON?

Go to Step 28

Go to Step 8

Inspect the following fuses for an open:

•	The PCM 10A fuse in the engine compartment fuse/relay center

•	The PCM/IGN 10A fuse in the IP fuse block

•	The CLS/PCM 10A fuses in the IP fuse block

Are the fuses OK?

Go to Step 9

Go to Step 10

Did the fuse in the fused jumper open?

Go to Step 12

Go to Step 13

Turn OFF the ignition.
Disconnect the BLU PCM connector.
Turn ON the ignition.
Connect a test light to ground and probe the PCM ignition feed circuits (terminal BLU 19 and BLU 61).

Does the test light illuminate?

Go to Step 17

Go to Step 11

Inspect for a short to ground in the circuit of the fuse that was open. Repair if necessary. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.
Replace the faulty fuse.

Is the action complete?

Go to Step 32

Repair the open in the PCM ignition feed circuit. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Repair the short to voltage in the MIL control circuit. Refer to Wiring Repairs in Engine Electrical - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Disconnect connector C017 (GRY).
Install a jumper between pins J and K in the PCM side of the connector.
Turn ON the ignition.
Probe the MIL circuit at the PCM connector with a fused jumper connected to the ground.

Is the MIL ON?

Go to Step 23

Go to Step 14

Inspect for an open in the MIL control circuit.

Was a problem found?

Go to Step 31

Go to Step 15

Inspect for an open ignition feed circuit or fuse (CLS/PCM) to the MIL.

Was a problem found?

Go to Step 30

Go to Step 16

Replace the IPC. Refer to Instrument Panel Cluster Replacement in Instrument Panel, Gauges and Cluster in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Probe the battery feed circuit in the BLU PCM connector (terminal BLU 20) with a test light connected to ground.

Does the test light illuminate?

Go to Step 22

Go to Step 29

Turn OFF the ignition.
Disconnect the CLR ECU connector C003.
Turn ON the ignition.

Is the MIL ON?

Go to Step 19

Go to Step 20

Turn OFF the ignition.
Disconnect the RED ECU connector C002.
Turn ON the ignition.

Is the MIL ON?

Go to Step 21

Go to Step 27

Repair the short to ground in the MIL control circuit between the CLR ECU and the BLK PCM connector. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Repair the short to ground in the MIL control circuit between the RED ECU connector and the IP panel. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Inspect for a faulty PCM ground connection at the engine block.
Inspect for continuity of the PCM ground circuits from the PCM connectors to ground.

Was a problem found?

Go to Step 30

Go to Step 28

Disconnect the CLR ECU connector C003.
Measure for continuity of the MIL circuit between C017 and C003 using a DVOM.

Is there continuity?

Go to Step 24

Go to Step 30

Disconnect RED ECU connector C003.
Measure for continuity of the MIL circuit between C017 and C002 using a DVOM.

Is there continuity?

Go to Step 25

Go to Step 30

Inspect for faulty ECU connections.

Was a problem found?

Go to Step 30

Go to Step 26

Inspect for faulty connections at connector C017.

Was a problem found?

Go to Step 30

Go to Step 27

Replace the ECU. Refer to Engine Control Unit Replacement .

Is the action complete?

Go to Step 32

Inspect for faulty PCM connections.

Was a problem found?

Go to Step 30

Go to Step 31

Repair the open battery voltage circuit. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Repair the circuit as necessary. Refer to Wiring Repairs in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Replace the PCM.

Important: If the PCM is faulty, reprogram the PCM. Refer to PCM Replacement/Programming in Engine Controls - 2.2L in the J Platform Service Manual.

Is the action complete?

Go to Step 32

Allow the engine to idle until the normal operating temperature is reached.
Inspect for any remaining DTCs that may be set.

Are any DTCs displayed that have not been diagnosed?

Go to the applicable DTC table

System OK