DTC P1825 or P1915

Diagnostic Instructions

 

     

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

 

     

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

 

     

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P1825:  Internal Mode Switch - Invalid Range

DTC P1915:  Internal Mode Switch Start/Wrong Range

Diagnostic Fault Information

 

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Transmission Range Signal A

P1825

P1915

P1915

P1825, P1915

Transmission Range Signal B

P1915

P1825

P1825

P1825, P1915

Transmission Range Signal C

P1915

P1825

P1825

P1825, P1915

Transmission Range Signal P

P1825

P1915

P1915

P1825, P1915

Ground

--

P1825

P1825

P1825, P1915

Typical Scan Tool Data

 

IMS A/B/C/P

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON, range selector in Park

Transmission Range Switch Signal A

LOW

LOW

HI

HI

Transmission Range Switch Signal B

HI

LOW

HI

HI

Transmission Range Switch Signal C

HI

LOW

HI

HI

Transmission Range Switch Signal P

LOW

LOW

HI

HI

HI = 12 volts

LOW = 0 volts

Circuit/System Description

 

The internal mode switch (IMS) assembly is a sliding contact switch attached to the control valve body within the transmission. The 4 inputs to the transmission control module (TCM) from the switch indicate which position is selected by the transmission manual shaft. The input voltage at the TCM 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. The IMS input parameters represented are transmission range signal A, Signal B, signal C, and signal P.

Conditions for Running the DTC

 

No OSS DTCs P0722 or P0723.

P1825

Vehicle speed sensor (VSS) is greater than 16 km/h (10 mph)

P1915

The transmission output shaft speed is less than 90 RPM.

Conditions for Setting the DTC

 

P1825

Any one or more of the following conditions:

     

The IMS signal circuit A, B, or P are Low in Park for greater than 1 second.

 

     

The IMS signal circuit A is Low in D6 for 8 seconds.

 

     

The IMS signal circuit C is High in D6 for 8 seconds.

 

     

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

 

     

The IMS signal circuit C is high in D6 for greater than 8 seconds and the engine torque is greater than 20 Nm (15 lb ft).

 

     

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.

P1915

The manual shift shaft switch assembly indicates a transitional state during the following sequence:

     

The engine speed is less than 50 RPM for more than 0.25 seconds.

 

     

The engine speed is 50-480 RPM for more than 0.07 seconds.

 

     

The engine speed is greater than 525 RPM for more than 3.25 seconds.

 

     

The transmission input shaft speed is greater than 250 RPM.

Action Taken When the DTC Sets

 

     

DTCs P1825 and P1915 are Type A DTCs.

 

     

The TCM commands maximum line pressure.

 

     

The TCM turns OFF all solenoids.

 

     

The TCM freezes transmission adaptive functions.

 

     

The TCM defaults the transmission to third gear if the current gear is 1st, 2nd, or 3rd; or fifth gear if the current gear is 4th, 5th, or 6th gear.

Conditions for Clearing the DTC

 

DTCs P1825 and P1915 are Type A DTCs.

Diagnostic Aids

 

     

The IMS is part of a wire harness, which connects electrically to the control solenoid (w/body and TCM) valve assembly and is serviced separately from the control solenoid (w/body and TCM) valve assembly. Inspect the IMS, harness, connector, and control solenoid (w/body and TCM) valve assembly pins for metallic debris. Use the J 35616 GM-approved terminal test kit for any test that requires probing the control solenoid (w/body and TCM) valve assembly harness connector or a component harness connector.

 

     

Inspect for a incorrectly adjusted range selector lever cable. Refer to Range Selector Lever Cable Adjustment .

 

     

Inspect the manual shaft detent assembly for proper alignment with the manual shaft detent lever. The manual shaft detent roller must be centered over the detent lever and not contact the IMS actuator arm.

Reference Information

 

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

     

Automatic Transmission Inline 16-Way Connector End View

 

     

Automatic Transmission Internal Connector End Views

 

     

Automatic Transmission Related Connector End Views

DTC Type Reference

     

Diagnostic Trouble Code (DTC) Type Definitions

 

     

Diagnostic Trouble Code (DTC) List/Type

Electrical Information Reference

     

Circuit Testing

 

     

Connector Repairs

 

     

Testing for Intermittent Conditions and Poor Connections

 

     

Wiring Repairs

Scan Tool Reference

     

Scan Tool Output Controls

 

     

Scan Tool Data List

 

     

Scan Tool Data Definitions

Special Tools Required

J 35616 GM-Approved Terminal Test Kit

Circuit/System Verification

 

Test for the correct operation of the IMS. Refer to Transmission Internal Mode Switch Logic .

If the IMS operation matches the IMS logic table, the system is functioning normally.

Circuit/System Testing

 

  1. Disconnect the IMS connector at the control solenoid (w/body and TCM) valve assembly. Ignition ON. The scan tool IMS A/B/C/P parameter should display HI for all four signal circuits.

If a signal circuit displays LOW, the control solenoid (w/body and TCM) valve assembly is faulty.

  1. Connect a 3-amp fused jumper wire between each transmission range signal circuit at the control solenoid (w/body and TCM) valve assembly and ground ensuring that the signal circuit displays LOW when connected to ground.

If a signal circuit remains HI when connected to ground, the control solenoid (w/body and TCM) valve assembly is faulty.

If the above two tests indicate correct TCM functions, the IMS is faulty.

Component Testing

 

Internal Mode Switch (IMS) Logic Table

Gear Selector Position

A

B

C

P

Park

LOW

HI

HI

LOW

Park/Reverse

LOW

LOW

HI

LOW

Reverse

LOW

LOW

HI

HI

Reverse/Neutral

HI

LOW

HI

HI

Neutral

HI

LOW

HI

LOW

Neutral/Drive 6

HI

LOW

LOW

LOW

Drive 6

HI

LOW

LOW

HI

Drive 4

LOW

LOW

LOW

LOW

Drive 3

LOW

HI

LOW

HI

Drive 2

HI

HI

LOW

LOW

Invalid

HI

HI

HI

HI

LOW

HI

HI

HI

HI

HI

HI

LOW

HI = Ignition voltage

LOW = 0 voltage

Repair Instructions

 

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

     

Internal Mode Switch (IMS) Replacement. Refer to Manual Shift Shaft Position Switch Replacement .

 

     

Control Solenoid (w/Body and TCM) Valve Assembly Replacement. Refer to Control Module References for replacement, setup, and programming.

 

     

Perform the Service Fast Learn Adapts .