Intermittent Ratio Codes Or Range Inhibit With No DTCs - keywords mil P0500 P0729 P0731 P0732 P0733 P0734 P0735 P0736 ses

This PI was superseded top update model years. Please discard PIP3598A.

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

There are 2 different symptoms which could be related to the same repair.

1. Intermittent no forward or reverse with possibly either a flashing PRNDL display or a "Range Shift Inhibited" message. There may not be any trouble codes stored in the transmission control module. When the condition is duplicated, the Tech II or Vehicle Data Recorder may display "commanded gear 0" and "current gear 0".
2. Transmission ratio code (i.e. P0729, P0731, P0732, P0733, P0734, P0735, and P0736) or any codes related to speed sensor stored in the TCM. May or may not be intermittent.

Snapshot the condition when it is occurring with either the Vehicle Data Recorder or the Tech II scan tool. Download the snapshot onto the TIS 2000 equipment and plot the 3 speed sensor readings (input speed, turbine speed and output speed). Monitor the sensor readings closely and look for a false speed reading and correct as necessary. Remember that the OSS or Output Speed Sensor is located in the Transfer Case on vehicle equipped with 4WD. If the OSS looks erratic, there could possibly be a mechanical concern within the transfer case causing the erratic signal (i.e. worn bushing, excessive endplay, etc.).

Note: Prior to any internal transmission repairs or transmission electrical component replacement on the C4500 model trucks please reference the latest version of TSB 02-07-30-042.

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.