Service Information
- Perform the Diagnostic System Check prior to using this diagnostic procedure:Diagnostic System Check - Vehicle
- Review the description of Strategy Based Diagnosis:Strategy Based Diagnosis
- An overview of each diagnostic category can be found here:Diagnostic Procedure Instructions
- DTC P073D
Unable to Engage Neutral
- DTC P073E
Unable to Engage Reverse
- DTC P07E4
Unable to Engage Park
- DTC P07E5
Unable to Engage Drive
- DTC P16F4
Control Module Transmission Range Switch Input Circuitry Performance
- DTC P1772
Powerflow Engaged Signal Message Counter Incorrect
- DTC P1773
Internal Mode Switch State Signal Message Counter Incorrect
- DTC P1778
Transmission Range Availability Signal Message Counter Incorrect
- DTC P1787
Unexpected Range Change Detected
- DTC P1789
Current Transmission Range Unknown
- DTC P187F
Transmission Range Primary Input Signal Message Counter Incorrect
- DTC P188A
Transmission Range Secondary Input Signal Message Counter Incorrect
For an overview of the component/system, refer to:Electronic Transmission Range Selector Description
Component | Description |
|---|---|
K20 Engine Control Module | The control module controls a series of actuators to ensure optimal vehicle performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the propulsion system actuators accordingly. |
K71 Transmission Control Module | The control module controls a series of actuators to ensure optimal vehicle performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the propulsion system actuators accordingly. |
K212 Gear Shift Control Module | The control module contains a microprocessor used to process input data to control outputs. The control module communicates with the control module k20 via serial data. |
Ignition=On
Conditions for Setting the DTCCommanded Transmission Range¿Transmission Range
Actions Taken When the DTC SetsDTCs listed in the DTC Descriptor category=Type B DTC
Conditions for Clearing the DTCDTCs listed in the DTC Descriptor category=Type B DTC
Diagnostic Aids- This DTC may be stored as a history DTC without affecting the operation of the device.
- If stored only as a history DTC and not retrieved as a current DTC, do not replace the device.
- To verify if DTC will reset, it may be necessary to shift through all gears (Park, Reverse, Neutral, and Drive).
Schematic Reference
Electronic Transmission Range Selector Schematics
Connector End View ReferenceMaster Electrical Component List
Electrical Information Reference- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool ReferenceCircuit/System Verification- Ignition » On / Vehicle » In Service Mode
- Verify there are no DTCs set related to the following component/system:T12 Automatic Transmission.
- If other DTCs are set
- If no other DTCs are set
- Transmission Range»P
- Verify the scan tool parameter:Transmission Range Control Valve 1 Position Switch=0.6 to 1.0 V
- If not between 0.6 and 1.0 V
Refer to:DTC P27EB, P27ED, or P27EE
- If between 0.6 and 1.0 V
- Verify the scan tool parameter:Transmission Range Control Valve 2 Position Switch=0.6 to 1.0 V
- If not between 0.6 and 1.0 V
Refer to:DTC P27EF, P27F1, or P27F2
- If between 0.6 and 1.0 V
- Verify the control module has the latest software:K71 Transmission Control Module
- If not the latest software
Program the control module:K71 Transmission Control Module
- If the latest software
- Verify the control module has the latest software:K20 Engine Control Module.
- If not the latest software
Program the control module:K20 Engine Control Module
- If the latest software
- Replace the component:K71 Transmission Control Module
- 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.
Verify the DTC does not set.
- If the DTC sets
Replace the component:K20 Engine Control Module
- If the DTC does not set
- All OK.
Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification
For control module replacement, programming, and setup refer to:Control Module References