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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 154 (Automatic Transmission - 4L80-E/4L85-E - Service, Diagnosis & Troubleshooting) >> Tow/Haul Switch/Indicator Always On or Inoperative >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 GMC Yukon XL and 2007 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step tests for a faulty tow/haul switch.
  2. 3:  This step tests for voltage input from the BCM to the tow/haul switch.
  3. 6:  This step tests for ground integrity.
Tow/Haul Switch/Indicator Always On or Inoperative

Step Action Yes No
1
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Cycle the tow/haul switch while observing Tow/Haul Mode on the scan tool.
Does the scan tool display Active when the switch is first pressed, and then Inactive when the switch is pressed again?
Go to Testing for Intermittent Conditions and Poor Connections Go to Step 2 
  1. Remove the connector from the tow/haul switch.
  2. Using the J 35616  GM-approved terminal test kit, install a fused jumper wire from terminals of the tow/haul switch connector. See Special Tools .
Does the scan tool Tow/Haul Mode indicate a status change?
Go to Step 7  Go to Step 3 
Using the DMM and the J 35616  , measure the voltage at the low reference of the tow/haul switch connector. See Special Tools .
Is ignition voltage measured?
Go to Step 6  Go to Step 4 
4 Using the DMM and the J 35616  , measure the voltage at the tow/haul switch signal circuit of the BCM. See Special Tools .
Is ignition voltage measured?
Go to Step 5  Go to Step 8 
5 Test the tow/haul switch signal circuit of the tow/haul switch for an open or shorted condition. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
Go to Step 9  Go to Testing for Intermittent Conditions and Poor Connections
Test the ground circuit of the tow/haul switch for an open or shorted condition. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?
Go to Step 9  Go to Testing for Intermittent Conditions and Poor Connections
7 Replace the tow/haul switch. Refer to Shift Lever Replacement .
Did you complete the replacement?
Go to Step 9  -
8 Test the BCM for proper operation. Refer to Diagnostic System Check - Vehicle .
Did you find and correct the condition?
Go to Step 9  -
9 After the repair is complete, observe Tow/Haul Mode on the scan tool display, while cycling the tow/haul switch.
Does the scan tool display Active when the switch is first pressed, and then Inactive when the switch is pressed again?
System OK Go to Step 1