Auxiliary Blower Motor Inoperative. GMC Truck Envoy - 2WD 2002

GM Service Manual Online

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Auxiliary Blower Motor Inoperative

Auxiliary Blower Motor Inoperative Body Type VIN 3

Test Description

The auxiliary system will not operate with the primary system in the DEFROST position.

Step	Action	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The auxiliary blower motor is inoperative in all blower motor switch positions.
1	Did you perform the HVAC Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Automatic
2	Important: The auxiliary blower motor only operates at MEDIUM and HIGH speed. When the auxiliary blower switch is placed in the lowest speed setting the air flow through the center console to the rear is provided by the primary blower motor. The air speed will vary depending on the front blower motor setting. Turn ON the ignition, with the engine OFF. Place the primary mode switch on the HVAC control module to the floor position. Place the front blower motor switch in the minimum speed position. Place the auxiliary blower motor switch in the medium speed position and the maximum speed position. Does the auxiliary blower motor operate in either of the speed positions?	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Cycle the auxiliary blower switch through all speed positions: Observe the Rear HVAC Fan Speed parameter in the Rear HVAC/RSA data list. Does the Rear HVAC Fan Speed parameter change with each command?	Go to Step 4	Go to Step 7
4	Turn the ignition OFF. Disconnect the auxiliary blower motor. Turn ON the ignition, with the engine OFF. Connect a test lamp between the auxiliary blower motor high speed control circuit and a good ground. Place the auxiliary blower motor switch in the maximum speed position. Does the test lamp illuminate?	Go to Step 5	Go to Step 7
5	Test the ground circuit of the auxiliary blower motor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 6
6	Inspect for poor connections at the harness connector of the auxiliary blower motor. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 8
7	Inspect for poor connections at the harness connector of the auxiliary HVAC control module. Refer to Wiring Repairs and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 10	Go to Step 9
8	Replace the auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement?	Go to Step 10	--
9	Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement . Did you complete the replacement?	Go to Step 10	--
10	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 3

Auxiliary Blower Motor Inoperative Body Type VIN 6

Step	Action	Values	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The auxiliary blower motor is inoperative in all speed positions from both the front and rear controls.
1	Did you perform the HVAC Diagnostic System Check?	--	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Manual
2	Turn ON the ignition, with the engine OFF. Place the front auxiliary blower motor switch in each speed position. Does the auxiliary blower motor operate in any of the speed positions?		Go to Auxiliary Blower Motor Malfunction	Go to Step 3
3	Turn ON the ignition, with the engine OFF. Place the front auxiliary blower motor switch in the Rear position. Place the auxiliary blower motor switch in each speed position. Does the auxiliary blower motor operate in any of the speed positions?	--	Go to Auxiliary Blower Motor Malfunction	Go to Step 4
4	Turn ON the ignition, with the engine OFF. With a scan tool, observe the Driver Override Switch parameter in the REAR HVAC/RSA data list. Place the front auxiliary blower motor switch in each position. Does the scan tool indicate that the Driver Override Switch parameter changes state?	--	Go to Step 5	Go to Step 6
5	Turn OFF the ignition. Disconnect the auxiliary blower motor connector. Turn ON the ignition, with the engine OFF. Connect a test lamp between the auxiliary blower motor supply voltage circuit and the auxiliary blower motor ground circuit. Place the auxiliary blower motor switch in the minimum speed position. Does the test lamp illuminate?	--	Go to Step 12	Go to Step 7
6	Test the auxiliary HVAC enable control circuit of the front auxiliary blower motor switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 14
7	Test the battery positive voltage circuit of the auxiliary blower motor control processor for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 8
8	Test the ground circuit of the auxiliary blower motor control processor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 9
9	Important: Ensure that the auxiliary blower motor control processor connector and the auxiliary HVAC control module connectors are connected during this step in order to avoid misdiagnosis. Place the auxiliary blower motor switch in each speed position. Measure the voltage from the auxiliary blower motor speed control circuit of the auxiliary HVAC control module to a good ground. Does the voltage measure near the specified value?	Low 6 V Med 4 V High 2.5 V Off Battery Voltage	Go to Step 11	Go to Step 10
10	Test the auxiliary blower motor speed control circuit of the auxiliary HVAC control module for an open or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 13
11	Test the auxiliary blower motor speed control circuit of the auxiliary HVAC control module for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 14
12	Inspect for poor connections at the harness connector of the auxiliary blower motor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 15
13	Inspect for poor connections at the harness connector of the auxiliary blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 16
14	Inspect for poor connections at the harness connector of the auxiliary HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 18	Go to Step 17
15	Replace the auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement?	--	Go to Step 18	--
16	Replace the auxiliary blower motor control processor. Refer to Auxiliary Blower Motor Processor Replacement . Did you complete the replacement?	--	Go to Step 18	--
17	Important: Perform the recalibration procedure for the auxiliary HVAC control module. Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement . Did you complete the replacement?	--	Go to Step 18	--
18	Operate the system in order to verify the repair. Did you correct the condition?	--	System OK	Go to Step 2