DTC Advanced Diagnostics: P1A4C

DTC P1A4C : TCM Internal Control Module Shift Parameter 1 Performance

General Description

When the transmission control module (TCM) shifting control malfunctions, it may cause unintended rapid deceleration, caused by the gear shifted to abnormal shift position. The TCM presumes that the gear is shifted to abnormal shift position from the value of the transmission fluid pressure sensor. If the TCM determines a shifting control malfunction, a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type

Execution	Continuous
Sequence	None
Duration	0.4 second or less
DTC Type	Two drive cycles, MIL on, shift position indicator blinks

Enable Conditions

Condition		Minimum	Maximum
Vehicle speed [Vehicle Speed]		54 mph (86 km/h)	-

[ ]: HDS Parameter

Malfunction Threshold

From the value of the transmission fluid pressure sensor, the actual shift position is presumed and the TCM determines as the gear shifted to inhibited shift position depending on the vehicle speed.

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

TCM internal circuit failure

Diagnosis Details

Conditions for setting the DTC

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the TCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on, the shift position indicator blinks, and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC

The shift position indicator comes off by turning the vehicle to the OFF (LOCK) mode. The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool clear command.