Fuel Pump Control Circuit Diagnosis
NOTE:
For information on testing relays and fuel system components, see SYSTEM & COMPONENT TESTING - CARS - PRIZM article. For complete wiring circuit of electrical components, see WIRING DIAGRAMS article.
- Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - PRIZM article. Repair any faults identified and go to next step.
- Turn ignition off. Install scan tool to Data Link Connector (DLC). See SELF-DIAGNOSTICS - PRIZM article. Remove bottom cushion of rear seat to gain access to fuel pump assembly access panel. Place a listening device on fuel pump assembly. Turn ignition on (engine off). Using scan tool, command fuel pump on and off, and listen for fuel pump operation. If fuel pump operates as commanded by scan tool, fuel pump circuit is okay. Problem could be intermittent or involve fuel system. See TROUBLE SHOOTING - NO CODES - CARS for intermittents or FUEL SYSTEM DIAGNOSIS for diagnosing fuel system. If fuel pump does not operate as commanded by scan tool, go to next step.
- If fuel pump does not operate continuously with ignition on (engine off), go to next step. If fuel pump operates continuously with ignition on (engine off), go to step 14 .
- Using scan tool, command fuel pump on and off, and listen for circuit opening relay operation. If circuit opening relay does not operate as fuel pump is commanded on and off by scan tool, go to next step. If circuit opening relay operates as fuel pump is commanded on and off by scan tool, go to step 9 .
- Turn ignition off. Remove circuit opening relay. Turn ignition on (engine off). Using a test light connected to ground, probe circuit opening relay cavities No. 2 and No. 3 (Black wires). If test light illuminates at both cavities, go to next step. If test light does not illuminate at both cavities, go to step 8 .
- Using a test light connected to ground, probe circuit opening relay cavity No. 4 (Green/Red wire) while commanding fuel pump on and off with scan tool. If test light does not illuminate as fuel pump is commanded on and off by scan tool, go to next step. If test light does illuminate as fuel pump is commanded on and off by scan tool, go to step 17 .
- Locate and repair open in circuit opening relay control circuit (Green/Red wire) between circuit opening relay and PCM connector C3 terminal No. 14 (connector C4 terminal No. 3 on models with 4-speed automatic transaxle). See WIRING DIAGRAMS article and Fig 1 and Fig 2 . If open circuit is not located and repaired, go to step 19 . If open circuit is located and repaired, go to step 20 .
- Locate cause for no ignition positive voltage to circuit opening relay (Black wires at cavities No. 2 and No. 3). See WIRING DIAGRAMS article. After repair, go to step 20 .
- Remove fuel pump assembly access panel. Disconnect Gray 5-pin connector. Using a test light connected to ground, probe fuel pump ignition positive voltage circuit (Blue/Black wire at terminal No. 4). Using scan tool, command fuel pump on. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
- Turn ignition off. Connect test light between Gray 5-pin connector terminal No. 5 (White/Black wire) and battery positive voltage. If test light does not illuminate, go to next step. If test light illuminates, go to step 13 .
- Repair open fuel pump ground circuit. Fuel pump ground circuit is White/Black wire between Gray 5-pin connector and ground point. Ground point is located behind left rear seat back trim panel. After repair, go to step 20 .
- Locate and repair open in fuel pump ignition positive voltage circuit (Blue/Black wire) between circuit opening relay terminal No. 1 and Gray 5-pin connector at fuel pump assembly terminal No. 4. After repair, go to step 20 .
- Check fuel pump ignition positive voltage circuit (Blue/Black wire) and fuel pump ground circuit (White/Black wire). See WIRING DIAGRAMS article. If circuits are okay, repair or replace fuel pump assembly. If circuits and fuel pump assembly are okay, go to step 18 . If fault was located and repaired, go to step 20 .
- Remove circuit opening relay. If fuel pump does not continue to operate, go to next step. If fuel pump continues to operate, locate and repair short to voltage in fuel pump ignition positive voltage circuit (Blue/Black wire). See WIRING DIAGRAMS article. After repair, go to step 20 .
- Turn ignition off. Using a test light connected to battery positive voltage, probe circuit opening relay control circuit at circuit opening relay terminal No. 4 (Green/Red wire). See WIRING DIAGRAMS article. Using scan tool, command circuit opening relay on and off. If test light stays illuminated even when relay is commanded off, go to next step. If test light does not stay illuminated even when relay is commanded off, go to step 17 .
- Locate and repair short to ground in circuit opening relay control circuit. Circuit opening relay control circuit is Green/Red wire between circuit opening relay terminal No. 4 and PCM connector C3 terminal No. 14 (connector C4 terminal No. 3 on models with 4-speed automatic transaxle). See WIRING DIAGRAMS article and Fig 1 and Fig 2 . If no fault is located and repaired, go to step 19 . If fault is located and repaired, go to step 20 .
- Replace circuit opening relay. After repair, go to step 20 .
- Replace fuel pump. After repair, go to step 20 .
- Replace PCM. After repair, reprogram PCM and go to next step. See PROGRAMMING in SELF-DIAGNOSTICS - PRIZM article.
- Operate vehicle under same conditions as recorded for original symptom. If system operates properly, system is okay at this time. If system does not operate properly, check circuit opening relay and fuel pump. Because temperature may affect circuit opening relay performance, allow vehicle to sit outside overnight and after running engine for 30 minutes. See SYSTEM & COMPONENT TESTING - CARS - PRIZM article.
Courtesy of GENERAL MOTORS CORP.