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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 89 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.0L)DIAGNOSTIC TESTSDTC P0201-P0208: INJECTOR CONTROL CIRCUITDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedures

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. With a scan, tool clear the DTCs. Idle engine at normal operating temperature. Using scan tool, monitor the misfire current counters. Are any of the misfire current counters incrementing? If yes, go to step  4. If no, go to next step.
  3. Using scan tool, observe FREEZE FRAME and/or FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions For Running DTC or as close to FREEZE FRAME and/or FAILURE RECORDS data as possible. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect affected fuel injector connector for DTC that is set. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION  table. Turn ignition on. Using a test lamp connected to ground, probe ignition voltage circuit at suspect fuel injector harness connector. Does the test lamp illuminate? If yes, go to next step. If no, go to step  11.
    DIAGNOSTIC TROUBLE CODE IDENTIFICATION

    DTC Injector No.
    P0201 (1) 1
    P0202 2
    P0203 3
    P0204 4
    P0205 5
    P0206 6
    (1) Injector No. 1 is the first injector on right (rear) cylinder head.
  5. Connect Fuel Injector Test Lamp (J-34730-2C) between suspect fuel injector harness connector. Start engine. Does the test lamp blink? If yes, go to step  9. If no, go to next step.
  6. Does the test lamp remain illuminated at all times? If yes, go to step  8. If no, go to next step.
  7. Check suspect fuel injector control circuit for short to voltage or open. Did you find and correct the condition? If yes, go to step  14. If no, go to step  10.
  8. Test the control circuit of the fuel injector for a short to ground. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  9. Check suspect fuel injector connector for poor connections. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  10. Check PCM connectors for poor connections. PCM is located in engine compartment, inside air filter housing. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  11. Repair open or short to ground in ignition voltage circuit between fuel injector and underhood fuse block. After repairs, go to step  14.
  12. Replace fuel injector. See FUEL SYSTEMS in appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  14.
  13. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  15. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.