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 MANUALSGMC1999SAVANA SPECIAL 7.4 JREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P1537-U1193DTC P1626DTC P1626: THEFT DETERRENT SYSTEM FUEL ENABLE CIRCUIT (5.7L "F" BODY)DIAGNOSTIC PROCEDURES
1999 GMC Savana Special 7.4 J
Diagnostic Procedures
1999 GMC Savana Special 7.4 JSECTION Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
- Turn ignition on, with engine off. Using scan tool, select DTC option and SPECIFIC DTC option, then enter this DTC. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS .
- If engine cranks, go to next step. If engine does not crank, diagnose theft deterrent system. See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.
- Turn ignition off. Disconnect BCM harness connector. Turn ignition on, with engine off. Check voltage at fuel enable circuit in BCM harness connector. If voltage reading is about 5 volts, go to next step. If voltage reading is not about 5 volts, go to step 7.
- Turn ignition off. Reconnect BCM harness connector. Turn ignition on, with engine off. Using DVOM connected to ground and in Hertz (Hz) scale, backprobe BCM harness connector theft deterrent fuel enable circuit. If DVOM reads 40-61 Hz, go to next step. If DVOM does not read 40-61 Hz, go to step 8.
- Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, see DIAGNOSTIC AIDS . If engine does not start or starts then dies, go to step 9.
- Check theft deterrent fuel enable circuit for open, short to ground or short to battery voltage. Repair as necessary. After repairs, go to step 12. If circuit is okay, go to step 9.
- Check for poor terminal connections of fuel enable circuit at BCM connector. Repair as necessary. After repairs, go to step 12. If terminal connections are okay, go to step 11.
- Check for poor terminal connections of fuel enable circuit at PCM connector. Repair as necessary. After repairs, go to step 12. If terminal connections are okay, go to next step.
- Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 12.
- Replace BCM. After replacing BCM, go to next step.
- Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2.
- Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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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.