Diagnostic Trouble Code (DTC) Information TCM-029A

Condition 

Fig 1: Identifying Transmission Control Module (TCM)

Courtesy of VOLVO CARS CORPORATION

The gear position sensor is integrated in the transmission control module (TCM) and provides information about the selected gear position. Built into the transmission control module (TCM) are two hall sensors. Their task is to detect whether the gear selector is in position.

For diagnostics there is a parallel hall sensor (2) that provides a reversed signal characteristic, so that the sum of the signal voltages from hall sensors (1) and (2) is constant. The signal voltage (0 and 5 volts) corresponds to the relevant gear selector lever position.

The diagnostic trouble code (DTC) is stored if the transmission control module (TCM) registers that the gear position is incorrect.

Substitute Value 

• None.

Possible Source 

• Incorrectly adjusted gear-shift position sensor
• Internal fault in the transmission control module (TCM).

Fault symptom[s] 

• The engine does not start.