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.

A dead zone exists in a range 10 counts above or below the auxiliary mode door max or auxiliary mode door min positions. When the auxiliary mode door actual data parameter is within the dead zone, the DTC will not set. If the auxiliary mode door commanded data parameter differs from the auxiliary mode door actual data parameter by 4 counts or more outside the dead zone, the DTC will set.
A damaged or broken auxiliary mode door and or actuator can cause this DTC to set.

DTC B3531

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 actuator Commanded data parameter and the auxiliary mode actuator Actual data parameter in the Auxiliary ECC Data list. Does the scan tool indicate that the auxiliary mode actuator Commanded data parameter is within the specified value of the auxiliary mode actuator Actual data parameter?	0-3 counts	Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS	Go to Step 3
3	Install the scan tool. Turn ON the ignition, with the engine OFF. With the scan tool, command the auxiliary mode actuator from floor (ON) to upper outlets (OFF). 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 floor to upper outlets?	5-250 counts	Go to Diagnostic Aids	Go to Step 4
4	Test the auxiliary mode door ignition 3 circuit of the auxiliary mode actuator for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 5
5	Test the 5 volt reference circuit of the auxiliary mode actuator for an open. high resistance or short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 6
6	Test the mode door control - auxiliary 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 14	Go to Step 7
7	Test the 5 volt reference circuit of front auxiliary HVAC control module for a short to ground. Refer to CIRCUIT TESTING and WIRING REPAIRS . Did you find and correct the condition?	-	Go to Step 14	Go to Step 8
8	IMPORTANT: The auxiliary mode actuator connector and the HVAC control module connector must be connected to correctly perform test. Turn on the ignition, with the engine off. With the scan tool, observe the auxiliary mode actuator actual parameter in the Auxiliary HVAC Data List. Connect a 3 amp fused jumper wire between the mode door control - auxiliary circuit of the auxiliary mode actuator and 5 volt reference circuit of the auxiliary mode actuator (drives the door to floor). Remove and reconnect the mode door control - auxiliary circuit of the auxiliary mode actuator to ground circuit of the auxiliary 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 11	Go to Step 9
9	Inspect the auxiliary mode actuator door and the auxiliary mode actuator for the following: Incorrectly installed auxiliary mode actuator. Broken or binding linkages or auxiliary mode actuator door. Obstruction that prevents the auxiliary mode actuator door from operating within it's full range of motion. Did you find and correct the condition?	-	Go to Step 14	Go to Step 10
10	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 14	Go to Step 12
11	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 14	Go to Step 13
12	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 14	-
13	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 14	-
14	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