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P1838




DTC P1824, P182A-P182F, P1838, or P1839

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 P1824
- Internal Mode Switch P Circuit High Voltage

DTC P182A
- Internal Mode Switch A Circuit Low Voltage

DTC P182B
- Internal Mode Switch B Circuit Low Voltage

DTC P182C
- Internal Mode Switch B Circuit High Voltage

DTC P182D
- Internal Mode Switch P Circuit Low Voltage

DTC P182E
- Internal Mode Switch-Invalid Range

DTC P182F
- Internal Mode Switch C Circuit High Voltage

DTC P1838
- Internal Mode Switch A Circuit High Voltage

DTC P1839
- Internal Mode Switch C Circuit Low Voltage

Diagnostic Fault Information






Typical Scan Tool Data






Transmission Internal Mode Switch Logic






Circuit/System Description

The automatic transmission manual shift shaft position switch assembly, also called the transmission internal mode switch assembly, is a dual sliding contact switch attached to the control valve body within the transmission. The 9 outputs from the switch indicate which position is selected by the transmission manual shaft. Four outputs (A, B, C, P) are range selection inputs to the transmission control module (TCM). Five outputs (R1, R2, D1, D2, S) are direction selection inputs to the hybrid powertrain control module. The input voltage at the modules is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as IMS Range and IMS Direction. The IMS Range input parameters represented are transmission range signal A, signal B, signal C, and signal P. The IMS Direction input parameters represented are transmission direction signal R1, signal R2, signal D1, signal D2, and signal Start.

Conditions for Running the DTC

* No OSS DTCs P0722 or P077B.

* The system voltage is 11-18 V.

P182E

* The engine run time is greater than 5 seconds.

* The system voltage is 11-18 V.

* The vehicle speed is less than 200 km/h (124 mph) for 5 seconds.

Conditions for Setting the DTC

Any one or more of the following conditions:

* The IMS signal circuit A, B, or P are Low in Park for greater than 8 seconds.

* The IMS signal circuit A is Low in D for 8 seconds.

* The IMS signal circuit C is High in D for 8 seconds.

* The TCM detects an invalid range from the IMS for 3.25 seconds.

* The IMS signal circuit C is high in D for greater than 8 seconds.

* Park/Neutral Switch equals P/N and the IMS state is not Park or Neutral, or the Park/Neutral switch is not Park or Neutral and the IMS state equals Park or Neutral for 4 seconds.

* Or the automatic transmission manual shift shaft position switch assembly indicates a transitional state for 8 seconds.

Action Taken When the DTC Sets

* The TCM commands maximum line pressure.

* The TCM turn OFF all solenoids.

* The TCM freezes transmission adaptive functions.

* The TCM defaults the transmission to 3rd gear if the current gear is 1st or 2nd gear, or 3rd gear if the current gear is 4th gear.

Conditions for Clearing the DTC

DTCs P1824, P182A-P182F, P1838, and P1839 are Type B DTCs.

Diagnostic Aids

The transmission internal mode switch connects electrically to the control solenoid valve assembly and is serviced separately from the control solenoid valve assembly. Inspect the transmission internal mode switch, harness, connector, and control solenoid valve assembly pins for metallic debris. Use a terminal test kit for any test that requires probing the control solenoid valve assembly harness connector or a component harness connector. The transmission internal mode switch assembly can be damaged by currents exceeding 2 mA. Test the transmission internal mode switch assembly for an open condition whenever a short to voltage condition is observed.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views Connector End Views By Name

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 Control Module References for scan tool information.

Circuit/System Verification





Test for the correct operation of the S2 transmission manual shift switch. Refer to Transmission Internal Mode Switch Logic Transmission Internal Mode Switch Logic.

If the S2 transmission manual shift switch operation matches the S2 transmission manual shift switch logic table, the system if functioning normally.

Circuit/System Testing

Note: Damage to the TCM may occur if the X1 16 way harness connector is disconnected before the X176 24 way connector or if the X1 16 way harness connector is connected after the X176 24 way connector.

1. Ignition OFF, remove the transmission pan. Refer to Transmission Fluid Pan Replacement Service and Repair.

2. Ignition OFF, disconnect the X2 harness connector at the B15 Transmission Internal Mode Switch.

3. Ignition OFF, all systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 10.0 ohms between the ground circuit terminal 5 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the Q8 control solenoid assembly.

4. Ignition ON, Verify the scan tool Internal Mode Switch A/B/C/P parameter displays HI for all four signal circuits.

• If not the specified value, test the signal circuits for a short to ground or short together. If the circuits test normal, replace the Q8 control solenoid valve assembly.

5. Ignition ON, test for 9.6-12.5 V between the voltage circuit terminal 2 and terminal 5.

• If not within the specified range, test the voltage circuit for an open/high resistance. If the circuit tests normal, replace the Q8 control solenoid assembly.

6. Ignition ON, Install a 3 A fused jumper wire between each signal circuit listed below and the ground circuit terminal 5. Verify the scan tool Internal Mode Switch A/B/C/P parameter is Low:

* Switch Signal A: terminal B to terminal 5

* Switch Signal B: terminal C to terminal 5

* Switch Signal C: terminal D to terminal 5

* Switch Signal P: terminal E to terminal 5

• If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the Q8 control solenoid assembly.

7. If all circuits test normal, replace the B15 Transmission Internal Mode Switch.

Component Testing










Repair Instructions

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

Note: Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection Control Solenoid Valve and Transmission Control Module Assembly Inspection for the following components before replacing the components.

* Manual Shift Shaft Position Switch Replacement Service and Repair for Transmission Internal Mode Switch replacement

* Wiring Harness Replacement Wiring Harness Replacement for Automatic Transmission Control Wiring Harness Extension Harness Assembly replacement

* Control Module References Control Module References for Control Solenoid Valve Assembly replacement, programming and setup

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