LCT1000 Transmission - DTC Diagnostic Tips - kw Allison fifth first fourth gear GMT800 hard harsh information intermittent no operation overheat performance

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Chevrolet Silverado and GMC Sierra trucks (GMT800) equipped with the Allison LCT1000 transmission may experience a malfunction indicator on and the vehicle has transmission related DTCs stored in the TCM.

The diagnostic processes and descriptions have not changed for any of the DTCs from the initial start of production 2001 through model year 2004. In model year 2001 there are 13 code numbers that are unique to that year but the same diagnostics are used in 2002 and later vehicles. These codes are the following with the current code they share:

Every effort is made to ensure that correct service information is available for all model years, but due to the vast amount of information that changes daily, the newest model year flow charts are updated first. To make sure that you are getting the latest diagnostic flow charts for the DTC you are diagnosing, you should use the 2004 model year flow charts on all GMT800 trucks equipped with the Allison M74 LCT1000 transmission.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

(01 - 04 Chevrolet Silverado) and (01 - 04 GMC Sierra)

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