P1915
DTC P1825 or P1915
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* 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
Typical Scan Tool Data
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
P1825
* The engine speed is greater than 500 RPM for 5 seconds.
* The ignition voltage is between 8.6 volts and 19.0 volts.
P1915
* No OSS DTCs P0722 or P0723.
* The transmission output shaft speed is less than 90 RPM or less.
Conditions for Setting the DTC
P1825
Any one of the following Fail Cases occur:
Fail Case 1
The TFP Switch 3 or TFP Switch 4 is pressurized with the commanded gear 1st locked and the IMS indicates a Drive 6/Drive 4 transitional state for 8 seconds or more.
Fail Case 2
The TFP Switch 3 or TFP Switch 4 is pressurized and the IMS indicates a Drive 3/Drive 2 transitional state for 8 seconds or more.
Fail Case 3
The TFP Switch 3 or TFP Switch 4 is pressurized and the IMS indicates a Neutral/Drive 6 transitional state for 1.25 seconds or more 6 times during the same ignition cycle.
Fail Case 4
The IMS indicates an invalid range or the IMS state and the ECM Park/Neutral Signal do not match for 6.25 seconds or greater.
Fail Case 5
The TFP Switch 3 or TFP Switch 4 is pressurized, the vehicle speed is 16 km/h (10 mph) or greater, and the IMS indicates a Reverse/Neutral transitional state for 3 seconds or greater.
P1915
The manual shift shaft switch assembly does not indicate Park or Neutral 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 200 RPM or greater.
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.
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.
2. 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
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
Important: Perform the Control Solenoid Valve and Transmission Control Module Assembly Inspection for the following components before replacing the components. Control Solenoid Valve and Transmission Control Module Assembly Inspection
* Internal mode switch (IMS) replacement - refer to Manual Shift Detent Lever with Shaft Position Switch Assembly and Park Pawl Actuator Removal and Manual Shift Detent Lever with Shaft Position Switch Assembly and Park Pawl Actuator Installation.
* Control solenoid (w/body and TCM) valve assembly replacement - refer to programming and relearning for replacement, setup, and programming.
* Perform the Service Fast Learn Adapts. Programming and Relearning