Circuit Description
Tow/Haul mode enables the operator to achieve enhanced shift performance when towing or hauling a load. When tow/haul is selected, the tow/haul switch input signal to the body control module (BCM) is momentarily toggled to zero volts. The BCM sends a serial data message to the powertrain control module (PCM) and instrument panel controller (IPC). The PCM extends the length of time between upshifts, increases transmission line pressure and the IPC illuminates the tow/haul indicator lamp. Cycling the tow/haul switch again disables the tow/haul mode and returns the transmission to a normal shift pattern.
Conditions for Running the DTC
| • | The battery voltage must be 9-16 volts. |
| • | Ignition switch in the RUN position. |
| • | The Tow/Haul switch must be activated. |
Conditions for Setting the DTC
| • | The signal circuit of the Tow/Haul switch is shorted to ground for approximately 3 minutes. |
| • | The Tow/Haul switch is activated, stuck, for approximately 3 minutes. |
Action Taken When the DTC Sets
Tow/Haul mode is inoperative.
Conditions for Clearing the MIL/DTC
| • | This DTC will clear on current status after the condition for setting the fault is corrected. |
| • | A history DTC will clear after 100 consecutive ignition cycles without a fault present. |
| • | History and current DTCs can be cleared using a scan tool. |
Diagnostic Aids
| • | Perform a visual inspection for loose or poor connections at all related components. |
| • | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The normal state is the state of the input before activation.
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The normal state is the state of the input before activation.
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After replacement of the BCM you must calibrate the new module for proper operation.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 6.0L or Diagnostic System Check - Engine Controls in Engine Controls - 8.1L |
Does the Transmission Preference parameter change states? | ON/OFF | Go to Diagnostic Aids | Go to Step 3 | |
3 |
Does the scan tool display OFF? | ON/OFF | Go to Step 6 | Go to Step 4 |
Test the signal circuit of the Tow/Haul switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 | |
5 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the Tow/Haul switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
7 |
Refer to Body Control Module Replacement in Body Control System. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Did you complete the replacement? | -- | Go to Step 9 | -- |
Replace the Tow/Haul switch. Refer to Shift Lever Replacement - On Vehicle in Steering Wheel and Column - Tilt. Did you complete the replacement? | -- | Go to Step 9 | -- | |
9 |
Does the DTC set? | -- | Go to Step 1 | System OK |
