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 MANUALSGMC1994C3500 HD 6.5 F, AUTOMATICREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - TESTS W/CODES - 6.5L DIESELTDC OFFSET PROGRAM PROCEDURE
1994 GMC C3500 HD 6.5 F, Automatic
TDC Offset Program Procedure
1994 GMC C3500 HD 6.5 F, AutomaticSECTION TDC Offset Program Procedure
This procedure allows PCM memory to be updated with correct TDC offset for vehicle. DTC 88 will be stored until procedure has been completed.
- Battery must be fully charged, engine operating at idle and vehicle at operating temperature.
- Connect Tech 1 scan tool. Select "OUTPUT TESTS" and "INJ. PUMP". Activate "TDC LEARN."NOTE: It will take PCM 20 seconds to learn TDC offset.
- Verify "TDC OFFSET" in data list. DTC will be stored if procedure has not been done correctly.
- If PCM fails to program TDC OFFSET, do the following:
- Check all PCM connection.
- Check Techline terminal/equipment for latest software version.
- Try again to program PCM. If it fails again replace PCM.
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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.