GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Cavalier (CNG) 🢒 Engine 🢒 Engine Controls - 2.2L (LN2) 🢒 Ignition Relay Diagnosis

Object Number: 654475 Size: LF
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The ignition relay is the positive voltage supply source for the following components:

    • The gas mass sensor/mixture control valve (GMS/MCV)
    • The fuel gauge select switch

The ignition relay coil is energized when the ignition switch is turned to the run or start positions. The ignition relay switch contact is supplied voltage at all times.

Test Description

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

  1. The System Check MUST be performed before proceeding with this diagnostic table. Failure to perform the System Check will result in mis-diagnosis.

    2.

  2. This step tests the AF ECU fuses for opens and also tests the voltage supply to the fuses.

    3.

  3. This step tests the battery positive and switched ignition voltage circuits to the AF ECU.

    4.

  4. This step tests the AF ECU ground circuits.

    5.

  5. This step inspects for proper operation of the FIL. If the FIL illuminates then the ignition relay is ON.

    6.

  6. This step inspects the ignition relays ability to turn OFF.

    7.

  7. This step tests the Ignition Relay coils ground circuit. If the test lamp illuminates then the Ignition relay must be faulty.

    8.

  8. This step indicates the components or circuits that may have caused a fuse to blow. Some components may require they be turned ON in order to blow the fuse. An example would be depressing the fuel gauge select switch in order to test the select switch circuit for a short.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Alternative Fuels (Engine Controls)?

--

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2
  1. Turn the ignition OFF.
  2. Remove and inspect the underhood CNG fuse and the instrument panel PCM fuse.

Is either fuse open?

--

Go to Step 13

Go to Step 3

3

  1. Install the CNG and PCM fuses.
  2. Turn the ignition On leaving the engine OFF.
  3. Probe both test terminals of each fuse using the J 35616-200 Unpowered Test Light connected to a known good ground.

Does the test lamp illuminate at all terminals?

--

Go to Step 5

Go to Step 4

4
  1. Inspect fuse terminal contact.
  2. Repair fuse terminal contact as necessary.
  3. Test the fuse supply source. Typically the source is a MAXI fuse, fusible link or a relay.
  4. Repair the fuse supply source as necessary.

Are all repairs complete?

--

Go to Step 22

--

5

  1. Turn the ignition OFF.
  2. Disconnect the AF ECU connectors. Refer to Engine Control Unit Replacement .
  3. Turn the ignition ON leaving the engine OFF.
  4. Probe the Battery Power and the two Ignition Power circuit terminals at the AF ECU connectors with the test lamp connected to a known good ground.

Does the test lamp illuminate at all terminals?

--

Go to Step 6

Go to Step 14

6

Probe all the ECU Ground circuit terminals at the AF ECU connectors with the test lamp connected to BATTERY POSITIVE.

Does the test lamp illuminate at all terminals?

--

Go to Step 20

Go to Step 14

7

  1. Turn the ignition OFF and wait 30 seconds.
  2. Observe the fuel indicator lamp (FIL) located in the fuel gauge select switch button.
  3. Turn the ignition ON leaving the engine OFF.

Did the FIL illuminate for a two second bulb check or stay ON?

--

Go to Step 9

Go to Step 8

8

With the ignition ON, backprobe the ignition relay switch load terminal (87) with the test lamp connected to a known good ground.

Is the test lamp illuminated?

--

Go to Fuel Indicator Lamp Inoperative - Alternative Fuels in Instrument Panel, Gauges, and Console

Go to Step 10

9

  1. With the ignition ON, backprobe the ignition relay switch load terminal (87) with the test lamp connected to a known good ground.
  2. Observe the test lamp as you turn the ignition OFF.

Is the test lamp illuminated with the ignition OFF?

--

Go to Step 15

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

10

With the ignition ON, backprobe the ignition relay switch supply terminal (30) with the test lamp connected to a known good ground.

Is the test lamp illuminated?

--

Go to Step 11

Go to Step 16

11

With the ignition ON, backprobe the ignition relay coil supply terminal (85) with the test lamp connected to a known good ground.

Is the test lamp illuminated?

--

Go to Step 12

Go to Step 17

12

  1. Disconnect the ignition relay connector (C004).
  2. With the ignition ON, connect the test lamp between the ignition relay coil supply terminal (85) and the ignition relay coil ground terminal (86).

Is the test lamp illuminated?

--

Go to Step 19

Go to Step 18

13

  1. Test for the short that caused the blown fuse.
  2. Possible shorts include the following:
    3. • CNG Fuse:
       - A shorted GMS/MCV or circuit
       - A shorted fuel gauge select switch circuit
       - A shorted lock-off solenoid or circuit
       - A shorted AF ECU or AF ECU Battery Power circuit
    • PCM Fuse:
       - A shorted Ignition Relay coil or circuit
       - A shorted AF ECU or AF ECU Ignition Power circuit
       - A shorted base vehicle circuit. Refer to Power Distribution Schematics in Wiring Systems in the J Platform Service Manual.
  3. Repair circuits or replace components as necessary.

Is the repair or replacement complete?

--

Go to Step 22

--

14

Repair the open in the AF ECU circuit that did not light the test lamp.

Is the repair complete?

--

Go to Step 22

--

15

Replace the stuck ignition relay or repair the Ignition Power circuit (relay terminal 85) shorted to battery positive.

Is the repair or replacement complete?

--

Go to Step 22

--

16

Repair the open in the ignition relay switch supply circuit terminal (30) between the relay and the circuit splice.

Is the repair complete?

--

Go to Step 22

--

17

Repair the open in the ignition relay coil supply circuit terminal (85) between the relay and the circuit splice.

Is the repair complete?

--

Go to Step 22

--

18

Repair the open in the ignition relay coil ground circuit terminal (86) between the relay and ground.

Is the repair complete?

--

Go to Step 22

--

19

Replace the ignition relay.

Is the replacement complete?

--

Go to Step 22

--

20
  1. Inspect for proper AF ECU terminal contact.
  2. Test for an open Class 2  serial data circuit between the splice and the AF ECU connector terminal.
  3. Repair terminal contact or wiring as necessary.

Was terminal contact or a wiring repair performed?

--

Go to Step 22

Go to Step 21

21
  1. Replace the AF ECU. Refer to Engine Control Unit Replacement .
  2. Program (flash) the replacement control module with the correct vehicle software and calibration.

Is the replacement complete?

--

Go to Step 22

--

22
  1. Remove all test equipment except the scan tool.
  2. Connect any dis-connected components, fuses, etc.
  3. Using a scan tool clear DTC Information from the AF ECU and the gasoline control module (VCM/PCM or ECM).
  4. Turn the ignition OFF and wait 30 seconds.
  5. Start the engine and operate the vehicle.
  6. Observe the fuel indicator lamp and the MIL.
  7. Observe vehicle performance and driveability.
  8. After operating the vehicle inspect BOTH control modules for stored DTCs.

Does the vehicle operate on CNG with normal driveability, no FIL/MIL illumination and no stored DTCs?

--

System OK

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)