Circuit Description
The winter mode allows the driver selection of a third gear start in order to reduce wheel spin under low traction conditions. Winter mode programming in the transmission control module (TCM) will command the 1-2 shift solenoid On and the 2-3 and 4-5 solenoids Off, enabling third gear for greater traction. The winter mode switch is a console mounted momentary contact switch located on the electronic PRNDL assembly. Accessory voltage is supplied to the electronic PRNDL assembly through the ELEC PRNDL fuse. When the winter mode switch is depressed, it momentarily contacts the switch signal circuit. The rear integration module (RIM) recognizes the voltage on the circuit and sends a class 2 serial data message to the dash integration module (DIM). The DIM sends a class 2 message to the engine control module (ECM). The ECM sends a request to the transmission control module (TCM) through the controller area network (CAN) to enable the winter mode program.
The TCM evaluates the request, and if operating conditions are correct for enabling the program, the TCM sends a confirmation message to the ECM. The ECM then requests the instrument panel cluster (IPC) to illuminate the winter mode indicator.
The winter mode feature remains enabled until the mode switch is pressed again, the transmission is placed in a lower gear, and certain vehicle speed, transmission fluid temperature, or accelerator pedal positions are exceeded. Once disabled, the TCM will resume a normal shift pattern.
Diagnostic Aids
| • | Test the instrument panel cluster (IPC) for proper operation and lamp illumination. Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. |
| • | Test the rear integration module (RIM) for proper winter mode switch input and output operation. Refer to Body Control System Description and Operation in Computer/Integrating Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Diagnose all communication and body DTCs first. The DTC may be the source of the symptom.
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No PRNDL display could be open in the electronic PRNDL assembly accessory circuit.
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This step tests the winter mode circuit by bypassing the electronic PRNDL assembly.
Step | Action | Value(s) | Yes | No | ||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Does the scan tool display DTCs that start with "U" or "B"? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 2 | |||||||||||||||||||||||
2 |
Does the winter mode indicator illuminate On and Off with switch operation? | -- | Go to Intermittent Conditions in Engine Controls - 3.6L (LY7) | Go to Step 3 | ||||||||||||||||||||||
3 | Is the winter mode indicator always On? | -- | Go to Step 9 | Go to Step 4 | ||||||||||||||||||||||
Move the gear selector from PARK through all gear positions while observing the electronic PRNDL display. Does the PRNDL display all gear positions? | -- | Go to Step 6 | Go to Step 5 | |||||||||||||||||||||||
5 | Test the accessory voltage circuit for an open. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | ||||||||||||||||||||||
Is the winter mode indicator illuminated? | -- | Go to Step 11 | Go to Step 7 | |||||||||||||||||||||||
7 | Test the electronic PRNDL ground circuits for an open. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||||||||||||||
8 | Test the winter mode switch signal circuit for an open. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||||||||||||||||||
9 | Test the winter mode switch signal circuit for a short to ground. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||||||||||||||||||
10 | While observing the winter mode indicator on the IPC, disconnect the electronic PRNDL assembly from the console wiring harness connector. Is the IPC winter mode indicator no longer illuminated? | -- | Go to Step 11 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||||||||||||||
11 | Replace the electronic PRNDL assembly. Refer to Front Floor Console Replacement in Instrument Panel, Gages, and Console. Is the action complete? | -- | Go to Step 12 | -- | ||||||||||||||||||||||
12 | After repairs, test the winter mode under the following conditions:
Does the winter mode operate as described? | -- | System OK | Go to Step 1 |
