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 transmission control module (TCM) to extend the length of time between upshifts and increase transmission line pressure. Cycling the tow/haul switch again disables tow/haul mode and returns the transmission to a normal shift pattern.

The Tow Mode switch remains closed, low voltage, for 600 seconds.

DTC P071A is a Type C DTC.

DTC P071A is a Type C DTC.

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

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Transmission General Information

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Transmission Control Module Scan Tool Information

1. Ignition ON, observe the scan tool Tow/Haul Mode parameter while pressing and releasing the tow/haul switch. The reading should change between Active and Inactive.
2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Important: Additional DTCs may set when disconnecting the automatic transmission inline 20-way connector.

1. Ignition OFF, disconnect the harness connector at the tow/haul switch.
2. Test for less than 10 ohm of resistance between the ground circuit terminal B and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the scan tool Tow/Haul Mode parameter is Inactive.

⇒	If not the specified value, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the BCM.

4. Install a 3A fused jumper wire between the signal circuit terminal A and the ground circuit terminal B. Verify the scan tool Tow/Haul Mode parameter is Active.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

5. If all circuits test normal, test or replace the tow/haul switch.

1. Ignition OFF, disconnect the harness connector at the tow/haul switch.
2. Test for infinite resistance between the signal terminal A and the ground terminal B with the switch in the open position.

⇒	If not the specified value, replace the tow/haul switch.

3. Test for less than 10 ohms between the signal terminal A and the ground terminal B with the switch in the closed position.

⇒	If greater than the specified range, replace the tow/haul switch.

4. Test for infinite resistance between each terminal and the switch housing/case.

⇒	If not the specified value, replace the tow/haul switch.

Perform the Diagnostic Repair Verification after completing the repair.