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 P0851: Park/Neutral Position (PNP) Switch Circuit Low VoltageDTC P0852: Park/Neutral Position (PNP) Switch Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Park/Neutral Signal | P0851 | P0852 | P0852 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine running, normal operating temperature Parameter Normal Range: 12 Volts = In-Gear, 0 Volts = Park/Neutral | |||
Park/Neutral Signal | Park/Neutral | In-Gear | In-Gear |
Circuit/System Description
The park/neutral position (PNP) switch is externally mounted on the transmission manual shaft. The switch consists of five separate circuits, four of which indicate gear selector position to the transmission control module (TCM), and one that indicates park/neutral position to the ECM. As the gear range selector lever is moved, the state of the P/N switch may change, causing the park/neutral signal circuit to open or close. An open circuit or switch indicates a drive range and a low voltage, 0 volts, signal at the engine control module (ECM). A closed circuit or switch indicates PARK or NEUTRAL and a high voltage, 12 volts, signal at the ECM. The ECM uses the PNP Switch status in order to enable starter operation.
Conditions for Running the DTC
| • | Ignition voltage is between 8-18 volts. |
| • | The engine speed is 1,000 RPM or greater. |
| • | The engine torque is at least 75 N·m (55 lb ft). |
| • | The throttle position is 8 percent or greater. |
| • | Vehicle speed is 10 km/h (6 mph) or greater. |
Conditions for Setting the DTC
P0851
The ECM detects the Park/Neutral switch signal equals 12 volts, high, when the PNP switch reports a Park/Neutral range for 3 seconds.
P0852
The ECM detects the Park/Neutral switch signal equals 0 volts, low, when the PNP switch reports a Drive range for 3 seconds.
Action Taken When the DTC Sets
| • | DTCs P0851 and P0852 are Type C DTCs. |
| • | The ECM uses PNP range for engine start-up. |
Conditions for Clearing the DTC
DTCs P0851 and P0852 are Type C DTCs.
Diagnostic Aids
It is possible for this DTC to set due to a stack-up or misalignment issue, where no electrical fault is present. Ensure the gear shift selector cable is properly adjusted and there are no service bulletins that address this concern before replacing parts.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Description and Operation
Electronic Component Description for park/neutral position switch information
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- If there are any other transmission related DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
- Ignition ON, observe the scan tool ECM PNP switch parameter while moving the gear shift lever from Park, to Reverse and through all the ranges. The parameter should display Park/Neutral when in Park or Neutral and In-Gear when in Reverse, Drive, or Drive Low.
- Observe the scan tool ECM PNP switch parameter while slowly moving the gear shift lever from Park, to Reverse and through all the ranges. Verify the gear position matches the scan tool parameter.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
| ⇒ | If not the specified value, refer to Floor Shift Control Cable Replacement. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the transmission range switch.
- Using the terminal test kit, connect a test lamp between battery positive voltage and terminal 12 of the PNP switch. Shift the transmission into Park and Neutral the test lamp should illuminate.
- Shift the transmission into Reverse and all other Drive ranges, the test lamp should not illuminate.
- Ignition ON, verify the scan tool ECM PNP switch parameter displays In-Gear.
- Install a 3A fused jumper wire between the park/neutral signal circuit terminal 12 and ground. Verify the scan tool ECM PNP switch parameter displays Park/Neutral.
| ⇒ | If the test lamp does not illuminate when in Park or Neutral, replace the PNP switch. |
| ⇒ | If the test lamp illuminates, replace the PNP switch. |
| ⇒ | If not the specified value, test the park/neutral signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If not the specified value, test the park/neutral signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
| • | Control Module References for ECM replacement, setup, and programming |
