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 MANUALSSATURN1999SL2 AUTOMATIC, MP6REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P1537-U1193DTC P1637DTC P1637: GENERATOR "L" TERMINAL CIRCUIT (4.8L, 5.3L & 6.0L "C" & "K" SERIES)DIAGNOSTIC PROCEDURES
1999 Saturn SL2 Automatic, MP6
Diagnostic Procedures
1999 Saturn SL2 Automatic, MP6SECTION 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.
- Start and operate engine at idle. Using scan tool, monitor generator "L" parameter. If scan tool indicates that generator "L" terminal is inactive, go to next step. If scan tool does not indicate that generator "L" terminal is inactive, see DIAGNOSTIC AIDS .
- Using a test light connected to ground, probe generator battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, diagnose charging system.
- Disconnect generator harness connector. Start engine. Check voltage between ground and generator harness connector terminal "B". If voltage reading is 10 volts or greater, go to step 11. If voltage reading is not 10 volts or greater, go to next step.
- Turn ignition off. Disconnect PCM harness connector. Check continuity between generator circuit at PCM and generator harness connector terminal "B". If continuity exists, go to next step. If continuity does not exists, go to step 8.
- Check continuity between battery ground and generator harness connector terminal "B". If continuity exists, go to next step. If continuity does not exist, go to step 9.
- Repair short to ground in generator circuit. After repairs, go to step 13.
- Repair open/high resistance in generator circuit. After repairs, go to step 13.
- Check terminal contact at PCM harness connector. Repair as necessary. After repairs, go to step 13. If terminal contact is okay, go to next step.
- Replace PCM. Program replacement PCM using required equipment.
- Check terminal contact at generator harness connector. Repair as necessary. After repairs, go to step 13. If connectors are okay, go to next step.
- Repair or replace generator. After repairing or replacing generator, 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 and REVIEW INFO option. If any undiagnosed DTCs are set, diagnose affected DTCs.
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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.