Circuit Description
The transmission internal mode 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 position of the transmission range selector. 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 .
If the TCM detects a combination of IMS signals that are invalid, or a transitional state between gear selector positions, while attempting to start the vehicle, then DTC P1915 sets. DTC P1915 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1915 Internal Mode Switch Does Not Indicate Park/Neutral (P/N) During Start
Conditions for Running the DTC
| • | The system voltage is 9-18 volts. |
| • | The ignition switch is in the START position for 2.5 seconds or more. |
| • | The engine speed is 450 RPM or more. |
Conditions for Setting the DTC
The IMS does not indicate PARK or NEUTRAL for 2 seconds when attempting to start the vehicle.
Action Taken When the DTC Sets
| • | The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records and the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records. |
| • | The TCM stores DTC P1915 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | The TCM clears the DIC message when the condition no longer exists. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
HI values for all signals in both Park and Drive 4 indicates the ground circuit is OPEN.
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With the 20-way connector disconnected, all signals should indicate HI.
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If one circuit affects the other, this indicates a short between the 2 circuits.
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This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Failure Records. Using the Clear DTC Information function erases the Failure Records from the TCM. Does each range selected match the scan tool IMS display? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
Does the IMS A/B/C/P parameter indicate the specified value for each range? | HI/HI/HI/HI | Go to Step 14 | Go to Step 4 | |
4 |
Refer to Range Selector Lever Cable Adjustment . Did the linkage require adjustment? | -- | Go to Step 19 | Go to Step 5 |
Do the scan tool IMS A/B/C/P signals all indicate HI? | -- | Go to Step 6 | Go to Step 10 | |
6 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the voltage measure ignition voltage at all 4 terminals? | -- | Go to Step 7 | Go to Step 11 |
Connect a fused jumper wire from terminal F of the J 44152 (signal circuit A) to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal circuit A is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 12 | Go to Step 8 | |
8 | Connect a fused jumper wire from terminal G of the J 44152 (signal circuit B) to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal circuit B is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 12 | Go to Step 9 |
9 | Connect a fused jumper wire from terminal H of the J 44152 (signal circuit C) to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal circuit C is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 12 | Go to Step 13 |
10 | Test the signal circuits of the IMS that did not indicate HI for a short to ground between the TCM and the AT Inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 |
11 | Test the signal circuits of the IMS that did not indicate ignition voltage for an open between the TCM and the AT Inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 |
12 | Test the affected signal circuits of the IMS for a shorted together condition between the TCM and the AT Inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 |
Test the signal circuits of the IMS for an open or shorted condition between the AT Inline 20-way connector and the IMS. Refer to Circuit Testing . Did you find the condition? | -- | Go to Step 16 | Go to Step 17 | |
14 | Test the ground circuit of the IMS for an open between the AT Inline 20-way connector and the chassis. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 15 |
15 | Test the ground circuit of the IMS for an open between the AT Inline 20-way connector and the IMS. Refer to Testing for Continuity . Did you find the condition? | -- | Go to Step 16 | Go to Step 17 |
16 | Replace the automatic transmission wiring harness assembly. Refer to Input Speed Sensor and Wiring Harness Removal in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 19 | -- |
17 | Replace internal mode switch, which is part of the manual shaft detent lever assembly. Refer to Control Valve Lower Body Disassemble in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 19 | -- |
18 | Replace the TCM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 19 | -- |
19 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 20 | Go to Step 2 |
20 | With a scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
