For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptor

DTC P0850: Park/Neutral Position (PNP) Switch Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Park/Neutral Signal | P0850 | P0850 | P0850 | --

### Typical Scan Tool Data

#### Park/Neutral Position Switch

Circuit | Normal Range | Short to Ground | Open/High Resistance | Short to Voltage
--- | --- | --- | --- | ---
Operating Conditions: Engine running, normal operating temperature, range selector in Park. Parameter Normal Range: 12 V = In-Gear, 0 V = Park/Neutral
Park/Neutral Signal | Park/Neutral | Park/Neutral | In-Gear | In-Gear

### Circuit/System Description

The transmission control module (TCM) provides the engine control module (ECM) shift position information through the high-speed communication on the controller area network (CAN). The automatic transmission shift position switch function is installed as one part of TCM. The shift range is calculated by TCM reading output voltage from gear lever position sensor installed TCM itself. The TCM and ECM use the decoded information for engine controls, starter enable, as well as determining the transmission shift pattern.

### Conditions for Running the DTC

• | The ignition voltage is between 10.2 V and 15.5 V.

• | The transmission is not in emergency mode.

• | TCM communication is normal.

• | Engine torque is equal to or greater than 75 N·m (55 lb ft).

• | Vehicle speed is equal to or greater than 10 km/h (6 MPH).

### Conditions for Setting the DTC

#### P0850

The ECM detects the park or neutral position signal when shift position reports a drive range.

### Action Taken When the DTC Sets

• | DTC P0850 is Type B DTC.

• | The ECM uses shift position switch range for engine start-up.

### Conditions for Clearing the DTC

DTC P0850 is Type B DTC.

### Reference Information

#### Schematic Reference

Automatic Transmission Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Description and Operation

Transmission Component and System Description

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. If there are any other engine or transmission communication related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

Note: It is especially important to closely observe the Park and Neutral to Drive transitional positions while moving the shift lever and observing for possible misalignment or slack in the shifter mechanism.

2. Ignition ON, observe the scan tool transmission range switch parameter in transmission data list while slowly moving the gear shift lever from Park and through all ranges. Verify the gear shift lever position matches the scan tool parameter.

⇒ | If not within the specified value, refer to range selector lever cable adjustment Range Selector Lever Cable Adjustment and Transmission Adaptive Functions.

3. Ignition ON, observe the scan tool transmission range switch parameter while slowly moving the gear shift lever from Park and through all ranges. Verify the gear shift lever position matches the scan tool parameter.

⇒ | If not within the specified value, replace the K71 Transmission Control Module (TCM).

4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

⇒ | If the DTC resets, replace the K20 Engine Control Module (ECM).

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | TCM, refer to Control Module References for replacement, setup and programming.

⇒ | Perform the Transmission Adaptive Functions.

• | ECM replacement, refer to Engine Control Module Replacement for LDK, Engine Control Module Replacement for LBS, LBX, LBY, Engine Control Module Replacement for LBW..

• | ECM, refer to Engine Control Module Programming and Setup for setup and programming.