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 Descriptors
DTC P0850: Park/Neutral Position (PNP) Switch CircuitDTC P0851: Park/Neutral Position (PNP) Switch Circuit Low Voltage
DTC P0852: Park/Neutral Position (PNP) Switch Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Starter Inhibit (PNP) Circuit | P0850, P0851 | P0850, P0851 | P0850, P0852 | -- |
Circuit/System Description
The transmission range (TR) switch is an integral part of the transmission control module (TCM). As the gear range selector lever is moved, the state of the Starter Inhibit Circuit may change, causing the circuit to open or close. An open circuit indicates a drive range and a low voltage signal, 0 volts, at the engine control module (ECM). A closed circuit indicates PARK or NEUTRAL and a high voltage, 12 volts, signal at the ECM.
The ECM uses the Starter Inhibit circuit status from the TCM in order to enable starter operation.
Conditions for Running the DTC
| • | Start Lock Driving voltage is within 6.0-16.0 volts. |
| • | Ignition voltage is greater than 6.5 volts. |
Conditions for Setting the DTC
DTC P0850 and P0851
The ECM detects "ON" signal from the Starter Inhibit circuit while the TCM is commanding the Starter Inhibit circuit "OFF" for 0.5 seconds.
DTC P0852
The ECM detects "OFF" signal from the Starter Inhibit Circuit while the TCM is commanding the Starter Inhibit Circuit "ON" for 0.5 second.
Action Taken When the DTC Sets
DTC P0850, P0851, and P0852 are Type C DTCs.
Conditions for Clearing the DTC
DTC P0850, P0851, and P0852 are Type C DTCs.
Reference Information
Schematic Reference
Automatic Transmission Controls Schematics
Connector End View Reference
Description and Operation
Electronic Component Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan information.
Circuit/System Verification
- If there are any other transmission DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
- 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
- Engine ON, observe the TR Sw. parameter while selecting each transmission range: P, R, N, D5, D4, D3, D2, and D1. Each selected transmission range should correspond to the correct scan tool PNP Switch parameter displayed.
- Observe the PNP Switch parameter (Engine Electrical/Theft Data) while selecting each transmission range: P, R, N, D5, D4, D3, D2, and D1. Each selected transmission range should correspond to the correct scan tool PNP Switch parameter displayed (Park/Neutral/In Gear).
| ⇒ | If not equal to the specified range, test the Starter Inhibit Circuit for a short to ground, an open/high resistance, or a short to voltage. If the circuit test normal, replace the TCM. |
| ⇒ | If not equal to the specified range, test the Starter Inhibit Circuit for a short to ground, an open/high resistance, or a short to voltage. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Perform the Control Module References for ECM or TCM replacement, setup, or programming.
