Pinpoint Test Q: The Blower Motor Does Not Operate Correctly
Climate Control System
Pinpoint Tests
Pinpoint Test Q: The Blower Motor Does Not Operate Correctly
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the blower motor relay coil receives ignition voltage through circuit CBP45 (YE). Voltage is supplied to the relay switch contact through circuit SBB35 (BU/RD). When the HVAC module commands the blower motor relay on, it supplies a ground to the blower motor relay coil through circuit CH123 (VT/GN). When the relay coil is energized, voltage is delivered to the blower motor and the blower motor control module through circuit CH402 (YE/GN). Ground for the motor is provided through circuit CH102 (YE/BU) from the blower control module. Ground for the blower control module is provided by circuit GD116 (BK/VT). The HVAC module sends a Pulse-Width Modulation (PWM) signal to the blower control module through circuit VH101 (WH/VT) to control the blower speed.
- DTC B10B9:12 Blower Control: Circuit Short to Battery - The module senses excessive voltage on the blower motor control PWM circuit, indicating a short directly to voltage.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Blower motor control module
- HVAC module
PINPOINT TEST Q: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY
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Q1 CHECK THE HVAC MODULE FOR DTCs
- Ignition ON.
- Check the HVAC module for DTCs.
- Is DTC B10B9:12 present?
Yes
GO to Q4.
No
GO to Q2.
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Q2 VERIFY THE BLOWER MOTOR OPERATION
- Ignition ON.
- Select PANEL on the HVAC module. Adjust the blower motor setting to LO and then to HI.
- Does the blower motor operate at any setting?
Yes
If the blower motor operates always in HI, GO to Q3.
If the blower motor is always ON, GO to Q6.
No
Go To Pinpoint Test P. Pinpoint Test P: The Blower Motor Is Inoperative
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Q3 CHECK CIRCUIT CH102 (YE/BU) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C271.
- Ignition ON.
- Does the blower motor operate?
Yes
REPAIR circuit CH102 (YE/BU) for a short to ground. TEST the system for normal operation.
No
INSTALL a new blower motor speed control module. TEST the system for normal operation.
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Q4 CHECK CIRCUIT VH101 (WH/VT) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: HVAC Module C228a.
- Ignition ON.
- Measure the voltage between blower motor speed control C271-3, circuit VH101 (WH/VT), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit VH101 (WH/VT) for a short to voltage. TEST the system for normal operation.
No
GO to Q5.
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Q5 CHECK CIRCUIT VH101 (WH/VT) FOR AN OPEN
- Ignition OFF.
- Measure the resistance between blower motor speed control C271-3, circuit VH101 (WH/VT), harness side and HVAC module C228a-14, circuit VH101 (WH/VT), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
REPAIR circuit VH101 (WH/VT) for an open. TEST the system for normal operation.
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Q6 CHECK CIRCUIT CH123 (VT/GN) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Relay.
- Disconnect: HVAC Module C228a.
- Measure the resistance between blower motor relay socket pin 86, circuit CH123 (VT/GN) and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to Q7.
No
REPAIR circuit CH123 (VT/GN) for a short to ground. TEST the system for normal operation.
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Q7 CHECK CIRCUIT CH402 (YE/GN) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Blower Motor C2004.
- Ignition ON.
- Measure the voltage between blower motor C2004-1, circuit CH402 (YE/GN), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CH402 (YE/GN) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new blower motor speed control. TEST the system for normal operation. If the blower motor still does not operate correctly, GO to Q8.
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Q8 CHECK THE MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Carry out the HVAC Module On-Demand Self Test. Alternate Diagnostic Methods - HVAC Module
- Operate the system.
- Does the concern return?
Yes
INSTALL a new HVAC module. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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