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 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. Refer to Transmission Internal Mode Switch Logic .
If the TCM detects an invalid transmission range with the engine running, then DTC P1825 sets. DTC P1825 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1825 Internal Mode Switch - Invalid Range
Conditions for Running the DTC
| • | The engine speed is greater than 500 RPM for 5 seconds. |
| • | The IMS indicates PARK or NEUTRAL for 1 second or greater. |
| • | The engine torque is greater than 50 N·m (37 lb ft). |
| • | The IMS indicates PARK or NEUTRAL for 1 second or greater. |
Conditions for Setting the DTC
The TCM detects an invalid combination of IMS signals for 8 seconds or greater.
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 commands an alternate coast shift pattern where downshifts occur at higher vehicle speeds while coasting. |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM assumes D4 for shifting. |
| • | 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 P1825 in TCM history during the consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the DTC
| • | A scan tool can clear the 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 all ranges indicate the ground circuit is OPEN.
-
With the 20-way connector disconnected, all signals should indicate HI.
-
If 1 circuit affects the other, this indicates a short between the 2 circuits.
-
This step tests the internal transmission harness. If no condition is found in the harness, the condition is in the switch.
Step | Action | Value | 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 Info 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 display the specified value for each range? | HI/HI/HI/HI | Go to Step 13 | Go to Step 4 | |
Do the scan tool IMS A/B/C/P signals all indicate HI? | -- | Go to Step 5 | Go to Step 9 | |
5 |
Does the voltage measure ignition voltage at all 4 terminals? | -- | Go to Step 6 | Go to Step 10 |
Connect a fused jumper wire from the transmission range Signal A circuit of the J 44152 to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When the transmission range Signal A circuit is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 11 | Go to Step 7 | |
7 | Connect a fused jumper wire from the transmission range Signal B circuit of the J 44152 to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When the transmission range Signal B circuit is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 11 | Go to Step 8 |
8 | Connect a fused jumper wire from the transmission range Signal C circuit of the J 44152 to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When the transmission range Signal C circuit is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 11 | Go to Step 12 |
9 | Test the transmission range signal circuits of the IMS that did not indicate HI for a short to ground between the TCM connector and the automatic transmission inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
10 | Test the transmission range signal circuits of the IMS that did not indicate ignition voltage for an open between the TCM connector and the automatic transmission inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
11 | Test the affected transmission range signal circuits of the IMS for a shorted together condition between the TCM connector and the automatic transmission inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 |
12 | Test the transmission range signal circuits of the IMS for an open or shorted condition between the automatic transmission inline 20-way connector and the IMS. Refer to Circuit Testing . Did you find the condition? | -- | Go to Step 15 | Go to Step 16 |
Test the ground circuit of the IMS for an open between the automatic transmission inline 20-way connector and the ground connection to the chassis. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | |
14 | Test the ground circuit of the IMS for an open between the automatic transmission inline 20-way connector and the IMS. Refer to Testing for Continuity . Did you find the condition? | -- | Go to Step 15 | Go to Step 16 |
15 | Replace the automatic transmission wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
16 | Replace the lever assembly manual shaft detent with internal mode switch. Refer to Manual Shift Detent Lever with Shaft Position Switch Assembly Removal . Did you complete the replacement? | -- | Go to Step 18 | -- |
17 | Replace the TCM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 18 | -- |
18 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 19 | Go to Step 2 |
19 | 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 |
