P0751-O/D SWITCH PRESSED (LO) MORE THAN 5 MINUTES (CONTINUED)
For the Transmission circuit diagram (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC - 48RE - SCHE-
MATICS AND DIAGRAMS)
For a complete wiring diagramRefer to Section 8W
Theory of Operation
The Tow/haul Overdrive OFF (control) Switch is located in the shift lever arm. The switch is a momentary contact
device that signals the ECM/PCM to toggle current status of the overdrive function. At ignition on, overdrive oper-
ation is allowed. Pressing the Tow/Haul Overdrive Off switch once causes the Tow/haul Overdrive OFF mode to be
entered and the Tow/Haul lamp to be illuminated. Pressing the switch a second time causes normal overdrive oper-
ation to be restored and the Tow/haul lamp to be turned off. The Tow/haul Overdrive OFF mode defaults to ON after
the ignition switch is cycled OFF and ON. The normal position for the control switch is the ON position. The switch
must be in this position to energize the solenoid and allow a 3-4 upshift. The control switch indicator light illuminates
only when the Tow/haul Overdrive Off switch is turned to the OFF position, or when illuminated by the transmission
control module.
•
When Monitored:
The engine must have been running for at minimum of 10 seconds. The circuit is tested every 440ms.
•
Set Condition:
This DTC will set if the Tow/Haul Overdrive Off Switch Sense circuit is held low for 5 minutes or more from the
time of switch closure or ignition on with the engine running.
Possible Causes
TOW/HAUL OVERDRIVE OFF SWITCH SENSE CIRCUIT SHORT TO GROUND
TOW/HAUL OVERDRIVE OFF SWITCH
ENGINE CONTROL MODULE
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 8 - ELECTRI-
CAL/ELECTRONIC CONTROL MODULES/TRANSMISSION CONTROL MODULE - DIAGNOSIS AND TESTING)
Diagnostic Test
1.
TOW/HAUL OVERDRIVE OFF SWITCH SENSE CIRCUIT
SHORT TO GROUND
Turn the ignition off.
Disconnect the PCM C3 harness connector.
Disconnect the Tow/Haul Overdrive Off switch harness connector.
Measure the resistance between ground and the Tow/Haul Overdrive
Off switch sense circuit in the PCM C3 harness connector.
Is the resistance below 5.0 ohms?
Yes
>> Repair the Tow/Haul Overdrive Off switch sense circuit for
a short to ground.
Perform RE TRANSMISSION VERIFICATION TEST VER -
1 (GAS). (Refer to 21 - TRANSMISSION/TRANSAXLE/
AUTOMATIC - 48RE - STANDARD PROCEDURE)
No
>> Go To 2
21 - 740
AUTOMATIC TRANSMISSION - 48RE - GAS - ELECTRICAL DIAGNOSTICS
DR/DH