P0850 - PARK / NEUTRAL SWITCH INPUT CIRCUIT

The Engine Control Module (ECM) and Transmission Control Module (TCM) use several sensors for the right operation of the engine and transmission and monitor these components. To determine the shift patterns, the TCM monitors the shift position switch and the park/neutral switch. The signal from both switches is highly dependent on the position of the shift lever. This signal is used to enable or disable engine start and cruise control.

The ECM continuously monitors the parking switch and compares its signal with the set values. In case it is out of the expected parameters, the DTC P0850 OBD2 will be set.

• Check Engine light ON.
• The cruise control may be locked.

Reasons for setting the P0850 OBDII diagnostic code:

• The parking switch may be corroded, causing excessive resistance in the circuit.
• The switch may be misaligned.
• The parking switch may be faulty.

Steps to troubleshoot the P0850 OBD2 error code:

• After locating your vehicle's parking switch, disconnect it and check for continuity at the various shift points. There should be continuity between both terminals of the switch when the shift lever is neutral. In case the transmission is in reverse, it should read an open circuit. If the switch does not change continuity, it may be faulty. If it changes the continuity in the wrong transmission position, it may not be installed properly. Make the proper adjustments.
• Using a wiring diagram from your vehicle as a reference, check the corresponding voltages for the parking switch. Generally, the input and output voltage of the switch should be 12 volts. If the result is not within specification, check that the resistance is as required and the switch is aligned. Replace the switch if necessary.
• Check that the switch cables or connectors are in good condition, fix or replace them if necessary.