Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 89 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.0L)DIAGNOSTIC TESTSDTC P0230: FUEL PUMP 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.
- 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.
- Turn ignition on, with engine off. With scan tool, command fuel pump ON and OFF. Does the fuel pump relay turn ON and OFF with each command? If yes, go to next step. If no, go to step 4.
- Using scan tool, observe and record Freeze Frame/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 recorded Freeze Frame/Failure Records data as possible. Does the DTC fail this ignition cycle? If yes, go to next step. If no, fault may be intermittent. See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition off. Disconnect fuel pump relay. Turn ignition on, with engine off. Probe the control circuit of the fuel pump relay with a test lamp connected to a good ground. Using scan tool, command fuel pump ON and OFF. Does test lamp turn ON and OFF with each command? If yes, go to next step. If no, go to step 6.
- Connect a test lamp between the control circuit of the fuel pump relay and ground circuit of relay. Using scan tool, command fuel pump ON and OFF. Does the test lamp turn ON and OFF with each command? If yes, go to step 9. If no, go to step 11.
- Does the test lamp remain illuminated with each command? If yes, go to step 8. If no, go to next step.
- Test the control circuit of the fuel pump relay for a short to ground or an open. Did you find and correct the condition? If yes, go to step 14. If no, go to step 10.
- Test the control circuit of the fuel pump relay for a short to voltage. Did you find and correct the condition? If yes, go to step 14. If no, go to step 10.
- Check fuel pump relay connector for poor connections. Did you find and correct the condition? If yes, go to step 14. If no, go to step 12.
- Check PCM connectors for poor connections. Did you find and correct the condition? If yes, go to step 14. If no, go to step 13.
- Repair open in fuel pump relay ground circuit. After repairs, go to step 14.
- Replace fuel pump relay. After repairs, go to step 14.
- Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE under PROGRAMMING. After repairs, go to next step.
- 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.
- 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.