• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
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.
• | No Transmission Mode Switch Signal DTC P1762. |
• | The engine speed is greater than 500 RPM for 5 seconds. |
• | The system voltage is 8-18 volts. |
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 .
Automatic Transmission Controls Schematics
Transmission General Description
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Transmission Control Module Scan Tool Information
J 35616 GM-Approved Terminal Test Kit
Turn ON the ignition, with the engine OFF. Cycle the tow/haul switch while observing the Tow/Haul Mode parameter on the scan tool.
⇒ | If the scan tool Tow/Haul Mode indicates a status change, replace the switch. |
⇒ | If Ignition Voltage is measured, test the ground circuit of the tow/haul switch for an open or shorted condition. |
⇒ | If Ignition Voltage is measured, test the signal circuit of the tow/haul switch for an open or shorted condition. |
⇒ | If Ignition Voltage is not measured, replace the BCM. |
Verify the Tow/Haul Mode parameter on scan tool while cycling the tow/haul switch.
Perform the Diagnostic Repair Verification after completing the repair.