Range Selector Displays Incorrect Range

Range Selector Displays Incorrect Range

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.

Circuit Description

The transmission range (TR)/internal mode switch (IMS) is part of the park/neutral position (PNP) and backup lamp switch assembly, which is internally mounted on the transmission manual shaft. The TR/IMS switch contains four internal switches that indicate the transmission gear range selector lever position. The powertrain control module (PCM) or transmission control module (TCM) supplies ignition voltage to each switch circuit. As the gear range selector lever is moved, the state of each switch may change, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The PCM/TCM detects the selected gear range by deciphering the combination of the voltage signals. The PCM/TCM compares the actual voltage combination of the switch signals to a TR/IMS switch combination chart stored in memory.

The PNP switch contains one internal switch that indicates the transmission gear range selector lever position when in Park and Neutral. The PCM/(ECM) engine control module supplies ignition voltage to the PNP switch circuit. As the gear range selector lever is moved, the state of the PNP switch changes, causing the circuit to open or close. An open circuit or switch indicates a high voltage signal. A closed circuit or switch indicates a low voltage signal. The PCM/ECM detects the Park and Neutral ranges by voltage signal.

Diagnostic Aids

Refer to Transmission Internal Mode Switch Logic Transmission Internal Mode Switch Logic for valid combinations of switch signal circuits A, B, C and Parity. On the table, HI indicates an ignition voltage signal. LOW indicates a zero voltage signal.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics 4L60-E/4L65-E/4L70-E - Automatic Transmission

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

Description and Operation

Transmission General Information Transmission General Information

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

Transmission Control Module Scan Tool Information (4L60-E) 4L60-E - Automatic TransmissionTransmission Control Module Scan Tool Information (6L45/6L50/6L80/6L90) 6L45/6L50/6L80/6L90 - Automatic Transmission

Special Tools

* J 35616 - GM-Approved Terminal Test Kit

* J 44152 - Jumper Harness (20 Pins)

Circuit/System Verification

Start and idle the engine. Using the scan tool, observe the IMS A/B/C/P parameter. Move the gear selector through all ranges and ensure that the scan tool IMS A/B/C/P parameter matches the gear selector for each selected range according to the Transmission Internal Mode Switch Logic Transmission Internal Mode Switch Logic table. On the table, HI indicates an ignition voltage signal. LOW indicates a zero voltage signal.

Circuit/System Testing

1. Using the scan tool, does the IMS A/B/C/P parameter display HI/HI/HI/HI for each range selected.

• If the IMS A/B/C/P parameter displays HI/HI/HI/HI for each range selected, repair the open in the IMS ground circuit.

2. Turn OFF the ignition. Disconnect the automatic transmission inline 20-way connector. Additional DTCs may set. Turn ON the ignition, with the engine OFF. Observe the IMS A/B/C/P parameter on the scan tool. The parameter should display HI/HI.

• If the IMS A/B/C/P parameter does not display HI/HI/HI/HI, repair the short to ground in the TR signal circuit that displayed LOW between the TCM and the automatic transmission 20-way inline connector.

3. Turn OFF the ignition. Install the J 44152 - jumper harness (20 pins), on the engine side of the automatic transmission inline 20-way connector. Turn ON the ignition, with the engine OFF. Using the DMM and the J 35616 - GM-approved terminal test kit, measure the voltage at each of the TR signal circuits at the J 44152 - jumper harness (20 pins).

• If the voltage is less than battery voltage, test the affected TR signal for an open between the TCM and the automatic transmission 20-way inline connector.

4. Turn OFF the ignition. Install the J 44152 - jumper harness (20 pins) on the transmission side of the automatic transmission inline 20-way connector. Measure the resistance for each TR signal circuit between the J 44152 - jumper harness (20 pins) circuit and the transmission case. The resistance should be greater than 10 ohms.

• If the resistance is less than 10 ohms, test the affected TR signal for a short to ground between the automatic transmission 20-way inline connector and the IMS switch.

5. Connect the automatic transmission 20-way inline connector. Turn ON the ignition, with the engine OFF. Place the range selector in D3. Observe the IMS A/B/C/P parameter on the scan tool. The IMS A/B/C/P parameter should display LOW/LOW/LOW/LOW.

• If any of the TR signal circuits do not display LOW when the range selector is placed in D3, test the affected TR signal for an open or high resistance between the automatic transmission 20-way inline connector and the IMS switch.

6. If all circuits and connections test normal, test or replace the IMS switch.

Component Testing

1. Disconnect the automatic transmission inline 20-way connector. Install the J 44152 - jumper harness (20 pins) on the transmission side of the connector and use J 35616 - GM-approved terminal test kit. Referencing Transmission Internal Mode Switch Logic Transmission Internal Mode Switch Logic , test for continuity between the IMS ground circuit and each TR signal circuit at the transmission side of the automatic transmission inline 20-way connector, when Transmission Internal Mode Switch Logic Transmission Internal Mode Switch Logic indicates the signal circuit should be LOW.

• If any TR signal circuits do not display continuity when the table indicates it should be LOW, test the affected TR signal circuit for an open or high resistance between the automatic transmission inline 20-way connector and the IMS switch.

2. Measure the resistance between each of the TR signal circuits and the transmission case. The resistance should be greater than 10 ohms.

• If any of the TR signal circuits display less than 10 ohms, test the affected TR signal for a short to ground.

3. If all circuits and connections test normal and the IMS switch tests normal, replace the TCM switch.

Repair Instructions

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

Control Module References Control Module References for TCM replacement, setup, and programming