Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The range fault can only be detected following a recalibration. The recalibration can only be initiated by removing the battery positive voltage circuit to the HVAC control module.
The calibration limit is 64-216 counts. An actual range below this limit suggests an obstruction, something stuck in the door which limits travel. An actual range above this limit suggests an excessive travel condition, damaged, or missing foam seals.
A damaged auxiliary mode door or a damaged actuator can cause this DTC to set.
An intermittent short to ground on the HVAC class 2 serial data circuit can set this DTC. Recalibrate actuators and test system.
If the condition is not present, refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS .

DTC B3764

Step	Action	Values	Yes	No
Schematic Reference: HVAC Schematics
1	Did you perform the HVAC Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Automatic
2	Install the scan tool. Turn ON the ignition, with the engine OFF. With the scan tool, observe the auxiliary mode door max. position data parameter and the auxiliary mode door min. position data parameter in the Auxiliary ECC Data List Subtract the auxiliary mode door min. position from the auxiliary mode door max. position. Does the result of the calculation indicate that the actual travel of the auxiliary mode actuator is within the specified range?	100-220 counts	Go to Step 3	Go to Step 8
3	With the scan tool, command the auxiliary mode actuator from upper outlets to floor. With the scan tool, observe the auxiliary mode actuator actual position. Does the scan tool indicate that the auxiliary mode actuator actual parameter changes within the specified range when it is commanded from upper outlets to floor?	5-250 counts	Go to Diagnostic Aids	Go to Step 4
4	Test the auxiliary mode door actuator ground circuit for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 13	Go to Step 5
5	Test the 5 volt reference circuit of the auxiliary mode actuator for a short to voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 13	Go to Step 6
6	Test the lower mode valve position sensor signal circuit for an open, short to ground or short to voltage. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 13	Go to Step 7
7	IMPORTANT: The auxiliary mode actuator connector and the HVAC control module connector must be connected to correctly perform this test. Turn on the ignition, with the engine off. With the scan tool, observe the auxiliary mode actuator actual parameter in the Primary ECC Data List. Connect a 3 amp fused jumper wire between the auxiliary mode door motor control circuit of the auxiliary mode actuator and the 5 volt reference circuit of the auxiliary mode actuator (drives the door to floor). Remove and reconnect the jumper wire between the auxiliary mode door control circuit of the auxiliary mode actuator to the ground circuit of the mode actuator (drives the door to upper outlets). Does the drive shaft of the auxiliary mode actuator rotate and do the counts change?	-	Go to Step 8	Go to Step 9
8	Inspect the auxiliary mode door and the auxiliary mode actuator for the following. Incorrectly installed auxiliary mode actuator. Broken or binding linkages or auxiliary mode door. Obstruction that prevents the auxiliary mode actuator from operating within it's full range of motion. Did you find and correct the condition?	-	Go to Step 13	Go to Step 10
9	Inspect for poor connections at the harness connector of the auxiliary mode actuator. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition?	-	Go to Step 13	Go to Step 11
10	Inspect for poor connections at the harness connector of the rear auxiliary HVAC control module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS . Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
11	IMPORTANT: Perform the recalibration procedure for the auxiliary mode actuator. Replace the auxiliary mode actuator. Refer to Mode Actuator Replacement - Auxiliary (Tahoe/Yukon) or Mode Actuator Replacement - Auxiliary (Suburban/Yukon XL) .Did you complete the replacement?	-	Go to Step 13	-
12	IMPORTANT: Perform the recalibration procedure for the HVAC control module. Replace the rear auxiliary HVAC control module. Refer to HVAC Control Assembly Replacement - Front Auxiliary .Did you complete the replacement?	-	Go to Step 13	-
13	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	-	Go to Step 2	System OK