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 MANUALSCHEVROLET1993SPORTVAN G30, VAN PASSENGER, 7.4 NREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 24 (ENGINE CONTROLS - TESTS W/CODES - 6.5L DIESEL)DIAGNOSTIC TROUBLE CODE CHARTSTDC OFFSET PROGRAM PROCEDURE

1993 Chevrolet Sportvan G30, Van Passenger, 7.4 N

TDC Offset Program Procedure

1993 Chevrolet Sportvan G30, Van Passenger, 7.4 NSECTION TDC Offset Program Procedure

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Vandura Special, 1994 GMC Vandura, 1994 GMC Rally Camper Special, 1994 GMC Rally, and 1994 GMC Forward Control. However, it is still accessible from the selected car via links, so may be relevant.

This procedure allows the PCM memory to be updated with the correct TDC offset for the vehicle.

DTC 88 will be stored until this procedure has been completed Set up:

Battery is fully charged.
Engine operating at idle.
Vehicle at operating temperature.
Connect Tech 1 Scan Tool
Select "OUTPUT TESTS" and "INJ. PUMP"
Activate "TDC LEARN"
NOTE: It takes PCM 20 seconds to learn TDC offset.
Verify "TDC OFFSET" in data list.
DTC 88 will be stored if procedure has not been done correctly.
NOTE: If the PCM fails to program the TDC OFFSET, do the following:
Check all PCM connections.
Check Techline terminal/equipment for latest software version.
Try again to program the PCM. If it fails again replace the PCM.

RENDER: 1.0x

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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.