• 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 P187E, P18AA, P18AB, P18AC, P18AE, P27EC, P27F0 will set with a hydraulic/mechanical condition.

For an overview of the component/system, refer to:Electronic Component Description

Ignition Voltage=Greater than 9 V

Frequency the DTC runs=Continuously—After the running conditions are met

Transmission Range Command=Park&Transmission Range Control Valve 1 Position Switch/Transmission Range Control Valve 2 Position Switch=Low—For greater than 1 s

DTCs listed in the DTC Descriptor category=Type B DTC

DTCs listed in the DTC Descriptor category=Type B DTC

• High resistance in the circuits of the component may set DTC P18AD without setting the DTC for the component:Q77D Transmission Control Solenoid Valve 4
• {If Equipped with ETRS}If DTC P0747, P0797, P187E, P18AA, P18AB, P18AC, P18AD, P18AE, P18E7, P18E8, P2714, P2715, P2718, P2720, P2721, P27EB, P27EC, P27ED, P27EE, P27EF, P27F0, P27F1, P27F2, or P2814 is setTransmission Fluid Pressure=172 kPa (25 PSI)—DefaultPark (P) range

• Park - Engine Running
• Reverse
• Neutral - Engine Running
• Drive Range, First Gear
• Drive Range, Second Gear
• Drive Range, Third Gear
• Drive Range, Fourth Gear
• Drive Range, Fifth Gear
• Drive Range, Sixth Gear
• Drive Range, Seventh Gear
• Drive Range, Eighth Gear
• Drive Range, Ninth Gear
• Fluid Passages

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Control Module References

1. Verify the condition does not exist:Incorrect fluid level or condition—Transmission»Refer to:Transmission Fluid Level and Condition Check
• If a condition exists

  Repair or replace as necessary

• If no condition exists
2. Verify there are no related DTCs set in the following system:
• B315A Transmission Range Control Valve 1 Position Switch
• B315B Transmission Range Control Valve 2 Position Switch
• B316 Transmission Park Valve Position Switch
• If a related DTC is set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle

• If a related DTC is not set
3. Verify DTC P187E is not set
• If DTC P187E is set
1. Verify the condition does not exist:Mechanical Condition@Mode Valve Position SwitchorPark Servo Piston Switch
• If a condition exists » Repair or replace as necessary
• If no conditions exist

  Refer to:Diagnostic Fault Information&Repair or replace as necessary

• If DTC P187E is not set
4. Ignition » On / Vehicle » In Service Mode
5. Perform the following action:Clear the DTCs.
6. 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 DTC P187E, P18AA, P18AB, P18AC, P18AD, P18AE, P27EC, P27F0, P27EB, P27ED, P27EE, P27EF, P27F1, P27F2 is not set

• If DTC P27EB, P27ED, P27EE, P27EF, P27F1, P27F2 is set

  Refer to:Diagnostic Trouble Code (DTC) List - Vehicle

• If DTC P187E, P18AA, P18AB, P18AC, P18AD, P18AE, P27EC, P27F0 is set

  Refer to:Diagnostic Fault Information&Repair or replace as necessary

• If none of the DTCs are set
7. All OK.

Perform the Diagnostic Repair Verification after completing the repair:Diagnostic Repair Verification

• Control Valve Body Cleaning and Inspection
• Control Valve Solenoid Body Cleaning and Inspection
• Control Valve Solenoid Body Replacement
• Mode Valve Position Switch Replacement
• Park Servo Piston Switch Replacement
• For control module replacement, programming, and setup refer to:Control Module References

Transmission Service Fast Learn Procedure—Perform only when the component/system is serviced.