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Inaccurate Speedometer - keywords cluster erratic gauge IPC odometer VSS

Subject:Inaccurate Speedometer

Models:2003-2008 Chevrolet Kodiak
2003-2008 GMC TopKick



This PI was superseded to update Recommendation/Instructions and models. Please discard PIT3294D.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Owners may comment of the speedometer being inaccurate. This could be caused by an incorrect PCM/ECM speed calibration.

Recommendation/Instructions:

Install The Tech 2 and follow the correct Speed Calibration Program:

6.6L RPO LMM

Doc ID 1868019

6.6L RPO LB7, LLY, LBZ

Doc ID 1212377

8.1L RPO L18

Doc ID 1549751

When entering the Tire Revolutions, the Tech 2 may ask for "Revolutions Per Mile" or "Revolutions Per Kilometer".

Vehicles with 225/70R19.5 tires enter "641" for RPM or 398 for RPK.

Vehicles with 245/70R19.5 tires enter "622" for RPM or 386 for RPK.

Please follow this diagnostic or repair 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.