Frederick J. Woodhouse

On my dashboard of my 2008 Impala LT where my gear indicator is
P R N [D] 3 2 1 there should be a box around which gear my car is in. Well, recently that box disappeared. Also, to check some of your settings like oil life the car has to be in park or it will say " Feature available in park". I continue to get this message even while the car is in park ever since the box disappeared. I am also getting the following trouble code p1915 & p0700

Frank3

There must be a switch or something. I had the same problem in my Tahoe. This had a shift on the column. To shift out of park you have to pull the lever towards you. If you pull the lever towards you while it is in drive, the circle around the D disappears. There must be a switch that senses if the lever is in towards to or away from you. If a console, I bet if the button is depress the same must happen. See if something is stuck, otherwiise it may bea bad switch or sensor.

Wrenchinonchevys

The p0700 is a DTC to tell the PCM there is a trams. Fault and turns on the MIL. The p1915 is Internal Mode Switch Does Not Indicate Park/Neutral (P/N) During Start. Possible switch or wiring to trans. The Internal mode switch is just like it sounds it is internal to transmission. The trans control module is not seeing that the vehicle is in park and is why you are getting that message.

Frederick J. Woodhouse

Thank you, were should I start with troubleshooting this issue? Could it be the TCM itself has gone bad?

Wrenchinonchevys

A TCM failure is not likely with a problem like this. Most likely going to be wiring. A good scan tool with engine and trans data will be required. There is a diagnostic flow chart for this DTC. Not sure how comfortable you are with electrical diagnosis but will try and post the flow chart later today.

Frederick J. Woodhouse

I mentioned the TCM because the stability light and check engine light are on and the service traction control message is being displayed as well. I changed out the throttle body unit and gas pedal as instructed from another tread with no luck and someone mentioned that it could be my TCM since the car is shifting hard and not acknowledging the gear posisiton.

Wrenchinonchevys

MIL and stability light most likely from the p0700. Will post flow chart below. Don't know if it will help. It is shifting hard with this DTC because the TCM will command full line pressure.



DTC P1820, P1822, P1823, P1825, P1826, 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 provide an overview of each diagnostic category.
DTC Descriptors
DTC P1820
Internal Mode Switch A Circuit Low Voltage

DTC P1822
Internal Mode Switch B Circuit High Voltage

DTC P1823
Internal Mode Switch P Circuit Low Voltage

DTC P1825
Internal Mode Switch – Invalid Range

DTC P1826
Internal Mode Switch C Circuit High Voltage

DTC P1915
Internal Mode Switch Does Not Indicate Park/Neutral (P/N) During Start

Diagnostic Fault Information
Circuits
Short to Ground
Open/High Resistance
Short to Voltage
TR Signal A
P1820, P1825, P1915
P1825, P1915
—
TR Signal B
P1825, P1915
P1822, P1825, P1915
—
TR Signal C
P1825, P1915
P1826, P1825, P1915
—
TR Signal P
P1823, P1825, P1915
P1825, P1915
—
Typical Scan Tool Data
Internal Mode Switch A/B/C/P
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 4
HI
LOW
LOW
LOW
Drive 4
HI
LOW
LOW
HI
Drive 4/Drive 3
LOW
LOW
LOW
HI
Drive 3
LOW
LOW
LOW
LOW
Drive 3/Drive 2
LOW
HI
LOW
LOW
Drive 2
LOW
HI
LOW
HI
Drive 2/Drive 1
HI
HI
LOW
HI
Drive 1
HI
HI
LOW
LOW
Invalid
HI
HI
HI
HI
LOW
HI
HI
HI
HI
HI
HI
LOW
HI = Ignition Voltage
LOW = 0 Voltage
Circuit/System Description
The internal module switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The 4 inputs to the transmission control module (TCM) indicate the transmission range selector position. The input voltage level at the TCM is high, B+, when the IMS is open and low when the switch is closed to ground. The 4 input parameters represented are Signals A, B, C and P – Parity. Refer to Transmission Internal Mode Switch Logic.

Conditions for Running the DTC
P1820, P1822, P1823, P1825
The engine is running for 5 seconds.
The IMS indicates PARK for 1 second or greater.
The engine torque is 50 Y (37 lb ft) or greater.
No engine torque malfunction.
P1826
No OSS DTC P0722 or P0723.
DTC P1826 has not passed this key cycle.
The engine is running for 5 seconds.
The IMS indicates PARK for 1 second or greater.
The engine torque is 50 Y (37 lb ft) or greater.
Vehicle speed is 16 km/h (10 mph) or greater.
No engine torque malfunction.
P1915
The engine speed is greater than 560 RPM for 5 seconds.
A CRANK request signal has been requested for 409 seconds or greater.
Conditions for Setting the DTC
P1820

The IMS signal A is continuously low this ignition cycle, and the IMS indicates transitional position D4–D3 for 8 seconds or greater.

P1822

The IMS signal B is continuously high this ignition cycle, and the IMS indicates transitional position D2–D1 for 8 seconds or greater.

P1823

The IMS signal P is continuously low this ignition cycle, and the IMS indicates transitional position N–D4 for 8 seconds or greater.

P1825

The TCM detects an invalid combination of IMS signals for 8 seconds or greater.

P1826

The TCM detects IMS signal C is high, while the gear radio indicates first, second, third, or fourth gear for 8 seconds or greater.

P1915

The IMS does not indicate PARK or NEUTRAL for 2 seconds or greater when attempting to start the vehicle.

Action Taken When the DTC Sets
DTC P1820, P1822, P1823, P1825, P1826, and P1915 are type B DTCs.
The TCM commands maximum line pressure.
The TCM assumes a D4 shift pattern.
The TCM freezes transmission adaptive functions.
Conditions for Clearing the DTC
DTC P1820, P1822, P1823, P1825, P1826, and P1915 are type B DTCs.

Reference Information
Schematic Reference
Automatic Transmission Controls Schematics

Connector End View Reference
Component Connector End Views
Inline Harness Connector End Views
Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
Control Module References for scan tool information

Special Tools
J 35616 GM 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. The scan tool should display LOW/HI/HI/LOW. Move the gear selector through all ranges and ensure the IMS A/B/C/P parameter matches the gear selector for each selected range.

Circuit/System Testing
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.
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.
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 terminal test kit, measure the voltage at each of the TR signal circuits at the J 44152.
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.
Turn OFF the ignition. Install the J 44152 on the transmission side of the automatic transmission inline 20-way connector. Measure the resistance for each TR signal circuit between the J 44152 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.
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.
If all circuits and connections test normal, test or replace the IMS switch.
Component Testing
Disconnect the automatic transmission inline 20-way connector. Install the J 44152 on the transmission side of the connector and use J 35616. Referencing 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 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.
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.
If all circuits and connections test normal and the IMS switch tests normal, replace the TCM switch.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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

© 2015 General Motors. All rights reserved.

Frederick J. Woodhouse

After replacing the throttle bottle, gas paddle and finally the transmission, the problem was still present. I than pulled the TCM to test the connectors and noticed that about 6 of the wires in the bundle had been chewed through. I then cut and soldered the bad cables and recovered the cable bundle and the car is back to running like a champ. I recommend that anyone one with a similar issue start with a visual inspection of the TCM cables then test the connectors before investing any serious money on anything else.