Diagnostic Instructions
DTC Descriptors
DTC P0851: Park/Neutral Position (PNP) Switch Circuit Low Voltage
DTC P0852: Park/Neutral Position (PNP) Switch Circuit High Voltage
Circuit/System Description
The park neutral position (PNP) switch consists of 6 separate circuits. The engine control module (ECM) provides a 12 volt signal circuit to the PNP switch. This circuit is used to signal to the ECM that the transmission is
either in park or neutral to enable starter motor operation. The transmission control module (TCM) provides 4 separate 12 volt signal circuits to the PNP switch. The 4 circuits are used to indicate the manual gear selected by the
vehicle operator. A ground circuit from the PNP switch completes the circuit for the internal switches of the PNP switch. Depending on the position of the shift lever, the individual switches may be either open or closed. When an internal PNP switch is in the
open position the ECM or TCM will see a high voltage, near B+ on the signal circuit. When a PNP switch closes, the ECM or TCM will see a low voltage, near zero volts.
Conditions for Running the DTC
P0851
| • | No transmission serial data DTC U0100. |
| • | The ignition voltage is 9-18 volts. |
| • | The transmission gear selector serial data message has been received and is valid. |
| • | The engine speed is less than 8192 RPM. |
P0852
| • | No transmission serial data DTC U0100. |
| • | No vehicle speed DTC P0722 or P0723. |
| • | No engine torque DTC P0101, P0102, P0103, P0106, P0107, or P0108. |
| • | No throttle position DTC P0120-P0123, P0220, P0222, P0223, or P2135. |
| • | The ignition voltage is 9-18 volts. |
| • | The transmission gear selector serial data message has been received and is valid. |
| • | The engine speed is greater than 400 RPM. |
Conditions for Setting the DTC
P0851
The park/neutral switch is high, near B+ for 3 seconds while the TCM is reporting the gear selector is in PARK or NEUTRAL.
P0852
The following conditions are met for at least 3 seconds:
| • | The P/N switch is low, 0 volts. |
| • | The TCM is reporting the gear selector is in PARK or NEUTRAL. |
| • | The throttle position sensor indicates greater than 10 percent. |
| • | The engine torque is greater than 75 N·m (55 lb ft). |
| • | The vehicle speed is greater than 10 km/h (6 mph). |
Action Taken When the DTC Sets
P0851 or P0852
| • | DTCs P0851 and P0852 are Type C DTCs. |
| • | The ECM disables engine cranking. |
Conditions for Clearing the DTC
DTCs P0851 and P0852 are Type C DTCs.
Diagnostic Aids
The scan tool refers to the PNP switch as the TR Switch.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Transmission Control Module Scan Tool Information
Special Tools
J 45681
Jumper Harness
Circuit/System Verification
- Ignition ON, verify with a scan tool the TR. Switch parameter corresponds to each gear position of the transmission when selected.
- 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.
Circuit/System Testing
- Ignition OFF, disconnect the PNP connector at the PNP switch.
- Ignition OFF, test for less than 3.0 ohms of resistance between the ground circuit terminal 7 and ground.
| ⇒ | If greater than the specified range, test and repair the ground circuit for an open/high resistance. |
- Ignition ON, test for 10-12 volts on the signal circuit between terminal 3 and ground.
| ⇒ | If not within the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
- Ignition ON, test for 10-12 volts on each signal circuit, between terminals 4, 5, 6, 8 and ground.
| ⇒ | If not within the specified range for each circuit, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the TCM. |
- If all circuits test normal, replace the PNP switch.
Repair Instructions
