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 26 (THEFT DETERRENT SYSTEM)DIAGNOSTIC TESTSDTC B2957: PASSLOCK(TM) SENSOR DATA CIRCUIT LOWTESTING
1999 GMC Forward Control 5.7 R, Automatic
DTC B2957: PASSLOCK(tm) SENSOR DATA CIRCUIT LOW: Testing
1999 GMC Forward Control 5.7 R, AutomaticSECTION Testing
WARNING: This page is about a different car, the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana, and 2001 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
- If theft deterrent diagnostic system check has been performed, go to next step. If theft deterrent diagnostic system check has not been performed, go to THEFT DETERRENT DIAGNOSTIC SYSTEM CHECK .
- Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC), located below steering column. See Figure . Momentarily turn ignition switch to CRANK position, not letting engine start, release ignition switch to RUN position. Monitor Passlock(tm) data voltage in Passlock(tm) module Data list. If scan tool indicates Passlock(tm) data voltage is 0.4-4.9 volts, check for intermittent or poor connections. See DIAGNOSTIC AIDS .
- Disconnect Passlock(tm) sensor 3-pin harness connector at base of steering column. Turn ignition switch to RUN position. Monitor Passlock(tm) data voltage in Passlock(tm) module Security Data list. If scan tool indicates Passlock(tm) data voltage as 4.9 volts or less, go to next step. If scan tool indicates Passlock(tm) data voltage as more than 4.9 volts, go to step 7 .
- Check for short to ground in Yellow wire (Passlock(tm) sensor signal circuit) between Passlock(tm) sensor harness connector terminal No. 1 and Passlock(tm) module harness connector terminal B7. If Yellow wire is okay, go to next step. If Yellow wire is not okay, repair as necessary. After repair, go to step 10 .
- Check Passlock(tm) module connector for intermittent or poor terminal contact. If terminal contact is okay, go to next step. If terminal contact is not okay, repair as necessary. After repair, go to step 10 .
- Check Passlock(tm) sensor connector for intermittent or poor terminal contact. If terminal contact is okay, go to next step. If terminal contact is not okay, repair as necessary. After repair, go to step 10 .
- Replace Passlock(tm) module. After repair, go to step 9 .
- Replace Passlock(tm) sensor. After repair, go to next step.
- Perform programming theft deterrent system components procedure. See PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS .
- Using scan tool, clear DTCs. Turn ignition switch to OFF position, then to RUN position. Select Passlock(tm) module DISPLAY DTC function. If DTC B2948 resets, go to step 3 . If DTC B2948 does not reset, system is okay at this time.
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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.