• | 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 0 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 ignition voltage is between 8 and 18 volts. |
• | The engine speed is between 500 and 6,500 RPM for 5 seconds. |
The tow mode switch remains closed, low voltage, for 600 seconds (10 minutes).
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
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for 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 diagnostic procedure.