Rear HVAC codes, B0145, B3531 and B0428

Tiny
EGUNS80
  • MEMBER
  • 2003 GMC ENVOY
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 148,000 MILES
I recently had my truck hooked up to an OBD computer got a code for my engine but it also gave my three codes for the rear HVAC B0145, B3531, and B0428. What are the for and how do I fix it?
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Monday, March 18th, 2019 AT 11:56 PM

1 Reply

Tiny
ASEMASTER6371
  • EXPERT
Good morning,

I will post the code descriptions below. There is no simple answer as diagnostics have to be done to determine the exact issue.

Roy

145 and the other codes. They are related to the same issue
DTC B0145

CIRCUIT DESCRIPTION
The following DTCs are for the auxiliary HVAC door actuators:
- B0145 is for the auxiliary mode actuator.
- B0428 is for the auxiliary air temperature actuator.
- B3531 is for the auxiliary console mode actuator

The auxiliary HVAC actuators are a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The auxiliary HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. This signal then is, converted into a count value where as 1 volt will equal 51 counts.

The auxiliary HVAC control module calibrates the travel range of the HVAC door actuators when it is initially powered by the battery positive voltage circuit.

During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position.

CONDITIONS FOR RUNNING THE DTC
- Battery voltage is 8.7-16.5 volts.
- The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The DTC sets when one of the following conditions are present for 2 minutes:
- The actual door position value for the actuator is less than 5 counts.
- The actual door position value for the actuator is greater than 250 counts.
- The actual door position is not near the commanded door position.
- An auxiliary door actuator door position change request is made.

ACTION TAKEN WHEN THE DTC SETS
The auxiliary HVAC control module will attempt to position the actuator to its default position. They are as follows:
- B0145 defaults the auxiliary mode actuator to the floor position.
- B0428 defaults the auxiliary air temperature actuator to the full hot position.
- B3531 defaults the console mode actuator to the floor position.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
- The history DTC will clear after 100 fault free ignition cycles.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
- If the condition is not present refer to in Diagnostic Aids.
- If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions:
- A misaligned actuator
- Broken linkages or binding linkages
- A broken door or a binding door
- An obstruction that prevents the door from operating within the full range of motion
- Missing seals to the door
- Poor connections at the harness connector of the door actuator
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Tuesday, March 19th, 2019 AT 5:39 AM

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