The internal mode switch (IMS) assembly is a sliding contact switch attached to the control valve body within the transmission. The nine 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 (HPCM). The input voltage at the module is high when the switch is open and low when the switch is closed to ground.

The HPCM compares the IMS range position to the IMS direction position to verify the transmission direction is correct.

Condition 1

The transmission direction, indicated by both the IMS range and direction switch circuits, are valid but do not match.

Condition 2

Condition 3

Condition 4

Condition 5

Condition 6

DTC P16F4 is a Type A DTC.

If IMS circuit DTCs P181C-P181F, P183A-P183F, P184A or P184B are set, perform those diagnostics first.

Schematic Reference

Hybrid Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. Clear the DTC information.
2. Turn the ignition OFF for 1 minute.
3. Turn the ignition ON.
4. Test for correct operation of the direction and range IMS switch circuits in every gear selection. Hold the selector in each gear position for at least 2 seconds. Refer to Typical Scan Tool Data.

⇒	If the Direction IMS operation does not match the logic table proceed with Circuit/System Testing.

⇒	If the IMS A/B/C/P operation does not match the logic table proceed to DTC P1824, P182A-P182F, P1838, or P1839 .

5. Retest for DTC P16F4.

⇒	If the DTC resets, program the PIM with the latest software version and recheck for DTCs. If the DTC resets after programming or if the PIM already contains the latest software version, replace the PIM.

1. Disconnect the transmission X176 24-way connector. Ignition ON. The scan tool IMS Status parameter should display HI for the R1, R2, D1, D2 and S signal circuit displays.

⇒	If a signal displays LOW, disconnect the PIM connector X1 and test the circuit for a short to ground.

⇒	If the circuit tests normal, replace the PIM.

2. Install DT-48493 to the vehicle harness connector X176. Verify that a test lamp illuminates between the Direction IMS switch ground circuit and battery positive.

⇒	If the test lamp does not illuminate, disconnect PIM connector X1 and test the ground circuit for an open, high resistance or short to voltage condition.

⇒	If the circuit tests normal, replace the PIM.

3. Connect a 3-amp fused jumper wire between each Direction IMS signal circuit at DT-48493 and the ground circuit terminal. The scan tool parameter should display LOW for each signal circuit when grounded.

⇒	If a scan tool parameter always displays HIGH, disconnect PIM connector X1 and test the circuit for an open, high resistance or short to voltage condition.

⇒	If the circuit tests normal, replace the PIM.

4. Disconnect the transmission 16-way X175 connector. Install DT-47825-10 to the vehicle harness. Connect a 3-amp fused jumper wire between the Starter signal circuit terminal and ground. The scan tool parameter should display LOW when the signal circuit is grounded.

⇒	If the scan tool parameter always displays HIGH, disconnect PIM connector X1 and test the circuit for an open, high resistance or short to voltage condition.

⇒	If the circuit tests normal, replace the PIM.

Important: The remaining diagnostic steps test the internal transmission components and circuits. The automatic transmission fluid pan assembly must be removed in order to perform the diagnostic tests.

5. Disconnect the IMS connector at the switch.

Important: Connect one end of the DT-48493 to the transmission connector. Use the other end as the terminal testing point.

⇒	Test the direction signal circuits and the ground circuit between the IMS and the transmission 24-way X176 connector for a short to ground, open, high resistance or short to voltage condition.

Important: Connect one end of the DT-47825-10 to the transmission connector. Use the other end as the terminal testing point.

⇒	Test the Starter signal circuit between the IMS and the transmission 16-way X175 connector for a short to ground, open, high resistance or short to voltage condition. The TCM is a pass-through of the Starter signal circuit and should be tested as a typical circuit path.

⇒	If the circuit, including the TCM, tests normal, replace the IMS switch.

Perform the Diagnostic Repair Verification after completing the repair.