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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1030 (Automatic Transmission - 4L80-E/4L85-E (Troubleshooting)) >> Troubleshooting >> Tow/Haul Switch/Indicator Always On or Inoperative >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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 Value(s) 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 Intermittent Conditions in Engine Controls - 4.8L, 5.3L, and 6.0L Go to Step 2 
2 
  1. Remove the connector from the tow/haul switch.
  2. Using the J 35616  GM terminal test kit, install a fused jumper wire from terminal S of the tow/haul switch connector.
Does the scan tool Tow/Haul Mode indicate a status change?		 - Go to Step 7  Go to Step 3 
3  Using the DMM and the J 35616  , measure the voltage at the low reference of the tow/haul switch connector.
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 body control module (BCM).
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 in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 9  Go to Intermittent Conditions in Engine Controls - 4.8L, 5.3L, and 6.0L
6  Test the ground circuit of the tow/haul switch for an open or shorted condition.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 9  Go to Intermittent Conditions in Engine Controls - 4.8L, 5.3L, and 6.0L
7 Replace the tow/haul switch.
Refer to Shift Lever Replacement (With Tow/Haul Switch)Shift Lever Replacement (Without Tow/Haul Switch) in Steering Wheel and Column.
Did you complete the replacement?		 - Go to Step 9  -
8 Test the BCM for proper operation.
Refer to Diagnostic Starting Point - Body Control System in Body Control System.
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 
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