P0854 Code: Drive Switch Input Circuit Low

What the P0854 code means

Some transmissions have a switch that confirms the shift lever is in D. The computer compares its signal with the transmission range sensor.

It is a simple switch, so the computer sees either a high or a low voltage depending on its position. The P0854 code is set when that signal sits below its minimum. A low signal usually comes from a signal wire shorted to ground or from a missing reference voltage.

When the signal fails, the transmission can go into limp mode or refuse certain gears. The transmission range sensor is tested the same way, so check it as well.

To confirm the diagnosis, unplug the component with the key on and watch what happens to the scan tool reading or to the code. If the value jumps to the opposite extreme, the wiring is fine and the component is the part pulling the signal to ground. If nothing changes, look for the short in the wire, starting where the harness rubs against the engine, the chassis or the exhaust.

P0854 code symptoms

• Check engine light on.
• Transmission in limp mode.

Likely causes of the P0854 code

1. Signal wire shorted to ground where the harness rubs against the engine, the chassis or a bracket.
2. Reference supply shorted. If several sensors fail at once, suspect the shared reference.
3. Damaged switch with an internal short.
4. Connector with water or corrosion, which creates a path to ground.

How to diagnose the P0854 code step by step

1. Read the switch value on the scan tool and compare it with what you expect.
2. Inspect the connector for corrosion, water or loose pins.
3. Check power and ground with the key on: the reference should be correct and the ground voltage drop should be under 0.1 V.
4. Measure the signal with the connector plugged in and see whether it changes with the lever position.
5. Do a wiggle test on the harness with the scan tool in graph mode.
6. Check continuity of each wire to the computer (under 1 ohm).

How to fix the P0854 code

• Repair the connector or the wiring.
• Replace the switch if the tests confirm it is bad.
• Correct the real condition if there is one.
• Clear the codes and verify with a road test.

Technical reference data

• The switch or sensor is powered from the computer. Check the values in the service manual.
• Reference values are only a guide, so look up the manufacturer data for your vehicle.
• Wire continuity should be under 1 ohm, and ground voltage drop under 0.1 V.

Brand-specific notes

The letter assignment and the location of the component change from one manufacturer to another, so check the manual for your vehicle before you start testing.

A P0854 code is easier to read when you compare the Drive switch with the range sensor on the scan tool. If the two disagree about the lever position, you have found the side that is lying.

Frequently asked questions about P0854