In vehicles equipped with an automatic transmission and four-wheel-drive, a sensor known as the transmission drive switch is used to tell the engine the computer what drive range has been selected on the transfer case. If a low voltage signal is received from the drive switch input circuit, a P0854 DTC will be stored in the ECU memory.
How Serious is the Code?
A P0854 diagnostic trouble code is actually quite serious, and can not only prevent the four-wheel-drive system from engaging. Transmission drive switch problems can cause harsh shifting and a complete failure to shift gears.
Symptoms of a P0854 include:
- 4WD system will not work
- Transmission seems to ‘slam’ into each gear
- Transmission won’t change gears
- Shorts in the wiring
- Corroded or broken connectors
- Faulty drive switch
- Faulty transfer case range sensor
How to Diagnose the Code?
Diagnosing a P0854 OBDII trouble code should begin with an examination of the wiring and connectors. If any of the wiring looks damaged or the connectors appear to be damaged, broken or corroded, they will have to be replaced. The drive switch itself will need to be tested to ensure that it is properly grounded and emits the correct amount of voltage. If not, it will need to be replaced. Should no transmission problems be found, the transfer case range sensor may need to be examined.
What Repairs Will Fix P0854?
- Repair or replace damaged wiring and connectors
- Replace drive switch
- Adjust transfer case range sensor
- Replace transfer case range sensor
- P0850 – Park/Neutral Switch Input Circuit
P0851 – Park/Neutral Switch Input Circuit Low
P0852 – Park/Neutral Switch Input Circuit High
P0853 – Drive Switch Input Circuit