Tow/Haul Switch/Indicator Always On or Inoperative

Tow/Haul Switch/Indicator Always On or Inoperative





Circuit/System Description

Tow/haul mode enables the operator to achieve enhanced shift performance when towing or hauling a load. When tow/haul mode is selected, the tow/haul switch input signal to the body control module (BCM) is momentarily toggled to zero volts. This signals the control solenoid valve assembly to extend the length of time between upshifts and elevate transmission line pressure. Cycling the tow/haul switch again disables tow/haul mode and returns the transmission to a normal shift pattern. The tow/haul switch is a momentary switch and is normally open. The internal spring in the switch will always cause the switch state to return to open when not held in to the closed position.

Diagnostic Aids

If the electrical circuit checks are OK and the tow/haul shift pattern is not occurring, there may be a mechanical/hydraulic condition that prevents tow/haul operation. Refer to Symptoms - Automatic Transmission (Symptoms - Automatic Transmission).

Reference Information
Schematic Reference

Automatic Transmission Controls Schematics (Diagrams)
Connector End View Reference

* Component Connector End Views (Connector Views)
* Inline Harness Connector End Views (Diagrams)

Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Ignition ON, cycle the Tow/Haul switch while observing the Tow/Haul switch parameter on the scan tool in the Transmission Controls Data list. The Tow/Haul switch parameter should change states from NO to YES, or YES to NO with each cycle of the switch.
2. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Circuit/System Testing

1. Ignition OFF, transmission in Park, disconnect the automatic transmission shift lever electrical connector.
2. Ignition OFF test for less than 1 ohm between terminal 2 on the automatic transmission shift lever vehicle harness connector and ground at the battery negative post.

• If greater than the specified valve test the ground circuit for an open/high resistance.

3. Ignition ON, test for greater than 11 volts on the signal circuit terminal 1 on the automatic transmission shift lever vehicle harness connector, and ground at the battery negative post.

• If not within the specified value, test the signal circuit for a short to ground or an open/high resistance. If all circuits test normal, replace the BCM.

4. Ignition OFF, test for less than 3 ohms between terminal 1 and terminal 2 on the automatic transmission shift lever component harness connector while depressing the Tow/Haul switch button.

• If greater than the specified value, replace the automatic transmission shift lever assembly.

5. If all circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Body Control Module (BCM) assembly replacement. Refer to Control Module References (Programming and Relearning) for replacement, setup, and programming.
* Perform the Shift Lever Replacement (Shift Lever Replacement).