GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Cavalier (CNG) 🢒 DTC 🢒 DTC P0201, P0202, P0203, or P0204

Circuit Description

The PCM controls fuel delivery and determines fuel system operation on Bi-fuel (KL6) vehicles. The PCM is not capable of operating the high current CNG fuel injectors. When CNG operation is commanded, the PCM grounds the AF enable circuit, which energizes the AF relay. The AF relay energizes all of the AF injector relays. The PCM injector control signals are routed through the AF injector relays to the fuel injector control module (FICM). The FICM generates duplicate control signals in order to operate the CNG injectors. When gasoline operation is commanded, the PCM opens the AF enable circuit, which de-energizes the AF relay, and all of the AF injector relays. The fuel injector control circuits are routed through the AF injector relays to the gasoline fuel injectors. A fused ignition voltage is supplied to all of the fuel injectors. The PCM monitors the status of each injector control circuit. DTC P0201-P0204 will set if there is condition on any one of the fuel injector control circuits, or AF injector relays.

Conditions for Running the DTC
    • The engine speed is more than 400 RPM.
    • The ignition voltage is between 6 and 18 volts.

Conditions for Setting the DTC
    • The powertrain control module (PCM) detects an incorrect voltage on a fuel injector control circuit.
    • The condition exists for 5 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    • Performing the Fuel Injector Coil Test on the fuel injectors may help to isolate an intermittent condition. Refer to Fuel Injector Solenoid Coil Test .
    • For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

  1. DTC P1020 indicates that a fuel injector circuit condition is detected while operating on CNG. If DTC P1020 and an individual fuel injector DTC are both set, diagnose P1020 first. If DTC P1020 is not set, the condition affects only the gasoline fuel injector related circuits. If DTCs P0201-P0204 are set without a DTC P1020 being set, the condition occurred during gasoline operation.

    2.

  2. The step determines if the condition exists. Remove the AF relay in order to ensure that the vehicle is operating on gasoline. Leave the relay out for the remainder of the diagnostic.

    3.

  3. This step verifies that an ignition voltage is supplied to the gasoline fuel injector. If the ignition voltage circuit is open a fuel injector DTC will set while operating on gasoline.

    4.

  4. This step tests the fuel injector and circuits to the gasoline fuel injector. If the test lamp blinks, then the AF injector relay and circuits are OK.

    5.

  5. This step tests the fuel injector control circuit from the PCM. The test lamp should blink while the engine is idling.

    6.

  6. This step tests if a ground is constantly applied to the fuel injector control circuit.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views

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

Observe the DTC information with a scan tool.

Did the DTC P1020 also set this ignition cycle?

Go to DTC P1020

Go to Step 3

3

Important: Verify that the gasoline fuel level is above 10% in order to prevent misdiagnosis. The misfire counters may not increment if the gasoline fuel level is below 10%.

  1. Remove the AF relay.
  2. Idle the engine at the normal operating temperature.
  3. Monitor the misfire current counters with a scan tool.

Are any of the misfire current counters incrementing?

Go to Step 5

Go to Step 4

4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 5

Go to Diagnostic Aids

5
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the gasoline fuel injector which displays the highest level of misfire.
  3. Probe the ignition voltage circuit of the gasoline fuel injector with a test lamp connected to a good ground.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 6

Go to Step 15

6
  1. Probe the injector control circuit with a test lamp connected to B+.
  2. Idle the engine, while observing the test lamp.

Does the test lamp blink?

Go to Step 12

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Remove the appropriate AF fuel injector relay.
  3. Probe the injector control circuit, from the PCM, with a test lamp connected to B+.
  4. Idle the engine, while observing the test lamp.

Does the test lamp blink?

Go to Step 9

Go to Step 8

8

Does the test lamp remain illuminated?

Go to Step 11

Go to Step 10

9

Test the control circuit of the fuel injector for an open, or a short to ground between the gasoline fuel injector and the relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 13

10

Test the control circuit of the fuel injector for an open, or a short to voltage between the PCM and the relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 14

11

Test the control circuit of the fuel injector for a short to ground between the PCM and the relay. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

12

Test for an intermittent and for a poor connection at the gasoline fuel injector. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 17

13

Test for an intermittent and for a poor connection at the AF injector relay. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 16

14

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems in the J Platform Service Manual.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

15

Repair the open or short to ground on the ignition voltage circuit of the gasoline fuel injector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the J Platform Service Manual.

Did you complete the repair?

Go to Step 19

--

16

Replace the AF injector relay.

Did you complete the replacement?

Go to Step 19

--

17

Replace the gasoline fuel injector. Refer to Fuel Injector Replacement in the J Platform Service Manual.

Did you complete the replacement?

Go to Step 19

--

18

Replace the PCM. Refer to Powertrain Control Module Replacement in the J Platform Service Manual.

Did you complete the replacement?

Go to Step 19

--

19
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 20

20

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK