Duramax LLY – REPROGRAMMING TDC OFFSET

TDC offset must be reprogrammed whenever the PCM, front cover, timing gears, timing chain, crankshaft position sensor, or other components affecting timing are replaced. The procedure for reprogramming TDC offset is as follows:

1. Verify that vehicle batteries are fully charged.
2. Start and run engine at curb idle speed.
3. Continue running engine at curb idle speed until coolant reaches normal operating temperature.
4. Connect Tech 1 scan tool to data link/diagnostic connector.
5. Select FO: OUTPUT TESTS from Miscellaneous Test menu.
6. Select FO: INJ PUMP.
7. Select TDC OFFSET LEARN.
8. Press Up Arrow key and PCM will learn engine top dead center offset value. This requires approximately 20 seconds.
9. Correct learned TDC Offset value should be between minus 0.25 and minus 0.75. If value is not within specified range, loosen injection pump and rotate it to correct value as follows:
• If value is between plus 1.0 and minus 0.25, rotate pump toward driver side to achieve specified value.
• If value is between minus 0.75 and minus 2.0, rotate pump toward passenger to achieve specified value.

NOTE: 1 mm pump movement in either direction results in approximately 2 degrees change.

Leave a Reply

Your email address will not be published. Required fields are marked *