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6L50/6L80/6L90 - Automatic Transmission




DTC P0850-P0852

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.

DTC Descriptors
DTC P0850
- Park/Neutral Position (PNP) Switch Circuit

DTC P0851
- Park/Neutral Position (PNP) Switch Circuit Low Voltage

DTC P0852
- Park/Neutral Position (PNP) Switch Circuit High Voltage

Diagnostic Fault Information





Typical Scan Tool Data





Circuit/System Description

The transmission manual shift shaft switch assembly, also known as the internal mode switch (IMS), is a sliding contact switch attached to the manual shift shaft inside the transmission case. The park/neutral position (PNP) switch is integrated into the IMS and connects to the transmission control module (TCM) lead-frame through a short wire harness. The circuit uses the TCM as a pass-through connector only.

The Park/Neutral Signal is sent from the park/neutral switch directly to the engine control module (ECM) and is used for engine start enable.

Conditions for Running the DTC

* Ignition voltage is between 11-18 volts.
* Engine Speed is 1000 RPM or greater.
* TP is 8 percent or greater.
* Engine torque is 75 Nm (55 lb ft) or greater.
* Vehicle speed is 10 km/h (6 mph) or greater.

Conditions for Setting the DTC

P0850 or P0851

The ECM detects the Park/Neutral switch signal equals 0 volts, Low, when the IMS reports a Drive range.

P0852

The ECM detects the Park/Neutral switch signal equals 12 volts, High, when the IMS reports a Park/Neutral range.

Action Taken When the DTC Sets

* DTC P0850, P0851, and P0852 are Type C DTCs.
* The ECM uses IMS Range for engine start-up.

Conditions for Clearing the DTC

DTC P0850, P0851, and P0852 are Type C DTCs.

Reference Information
Schematic Reference

* Automatic Transmission Controls Schematics (6L45/6L50/6L80/6L90 - Automatic Transmission)
* Engine Controls Schematics ([1][2]Electrical Diagrams)

Connector End View Reference

* Component Connector End Views (Connector End Views By Name)
* Inline Harness Connector End Views (Connector End Views By Number)

Description and Operation

* Transmission General Description (Transmission General Description)
* Transmission Component and System Description (Transmission Component and System Description)
* Electronic Component Description (Electronic Component Description)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information
Special Tools

DT-47825-10 - Jumper Harness

For equivalent regional tools, refer to Special Tools (6L45/6L50/6L80/6L90 - Automatic Transmission).

Circuit/System Verification

1. If there are any other transmission DTCs set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Ignition ON, observe the scan tool ECM Park/Neutral switch parameter while moving the gear shift lever from Park and through all ranges. The parameter should display Park/Neutral when in Park or Neutral and In-Gear when in Reverse or Drive.
3. Observe the scan tool TCM IMS parameter while slowly moving the gear shift lever from Park through all ranges. Verify the gear position matches the scan tool parameter. Refer to Transmission Internal Mode Switch Logic (Transmission Internal Mode Switch Logic).

• If not the specified value, refer to Range Selector Lever Cable Adjustment (4L60-E/4L65-E/4L70-E - Automatic Transmission).

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.

Circuit/System Testing

1. Ignition OFF, disconnect the T12 automatic transmission assembly X1 connector.
2. Install the DT-47825-10 - jumper harness to the X1 vehicle wire harness connector.
3. Ignition OFF, test for less than 5 ohms between terminal 5 at the DT-47825-10 - jumper harness and ground at the transmission case.

• If greater than the specified value, test the ground circuit for an open/high resistance.

4. Ignition ON, test for 11-13 volts on terminal 3 at the DT-47825-10 - jumper harness and ground at the transmission case.

• 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.

5. Ignition OFF, disconnect the DT-47825-10 - jumper harness from the X1 vehicle harness connector.
6. Connect the X1 vehicle harness connector to the Q8 control solenoid valve assembly.
7. Remove the transmission fluid pan. Refer to Automatic Transmission Fluid, Fluid Pan and/or Filter Replacement (Automatic Transmission Fluid, Fluid Pan and/or Filter Replacement).
8. Disconnect the B15 automatic transmission internal mode switch electrical connector from the K71 TCM.
9. Ignition ON, test for 11-13 volts between terminal F on the K71 TCM and ground at the transmission case.

• If not within the specified range, replace the Q8 control solenoid valve assembly.

10. If all circuits test normal, replace the B15 automatic transmission internal mode switch.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Control Module References (Programming and Relearning) for control solenoid valve assembly or ECM replacement, setup, and programming.

Note: If the IMS switch has been replaced, inspect the valve body detent spring to be sure it is centered over the detent lever. This prevents the detent spring from hitting the IMS switch.

* Manual Shift Shaft Position Switch Replacement (6L45/6L50/6L80/6L90 - Automatic Transmission) for IMS replacement.

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