Tech Tip: GM Truck HVAC Out of Control

Tech Tip: GM Truck HVAC Out of Control

Some GM truck and SUV owners may comment that they cannot control the heating, ventilation and air conditioning (HVAC) system. Others may comment that the HVAC system defaults to the Defrost mode. If a technician checks for diagnostic trouble codes (DTC), they could find that the following DTCs have set ....

By Rich Diegle
ALLDATA Senior Automotive Editor

Some GM truck and SUV owners may comment that they cannot control the heating, ventilation and air conditioning (HVAC) system. Others may comment that the HVAC system defaults to the Defrost mode.

If a technician checks for diagnostic trouble codes (DTC), they could find that the following DTCs have set:
B0229 – Recirculation Actuator
B0414 – Left Air Temperature Actuator
B0424 – Right Air Temperature Actuator
B3770 – Mode Actuator Cause

The problem may be that the HVAC actuator harness has contacted a sharp edge on the instrument panel support brace, causing a rub through condition and a grounding of the actuator control and/or feedback circuits.

Models affected: 2003-’05 Cadillac Escalade, Escalade ESV, Escalade EXT; Chevrolet Avalanche, Silverado (pictured), Suburban, Tahoe; and GMC Sierra, Yukon, Yukon XL

1. To repair the problem, locate the HVAC actuator harness contact point shown by the arrow in Figure 1.

Note: The illustration is of the instrument panel with the instrument panel compartment door opened and folded downward. The actuator harness is located in the left side of the opening in the instrument panel.

2. Inspect the HVAC actuator harness for contact with the instrument panel support brace. Repair any damage to the actuator harness wiring.

3. Install a protective plastic conduit over the harness.

4. Install friction tape over the sharp edge of the instrument panel brace to insulate it.

5. Clear the diagnostic trouble codes and verify proper HVAC system operation.

ALLDATA Senior Automotive Editor Rich Diegle is an Advanced Engine Performance Certified, ASE Master Technician with an AA Degree in automotive technology and 23 years of dealership and independent shop experience.

Courtesy of ALLDATA.

For information on products offered by ALLDATA, visit www.alldata.com.

You May Also Like

Were things better when they were simpler? Probably not.  

Last month, Andrew Markel purchased a 1982 Chrysler New Yorker for $1,500.

1982 Chrysler New Yorker

Last month, I purchased a 1982 Chrysler New Yorker for $1,500. The car was previously owned by a technician who was moving to Arizona. It had 67,000 original miles. It would be my “beater with a heater” for this winter.

Under the hood is a 318 V8 with a Lean Burn feedback carburetor with a rudimentary engine control module attached to the air cleaner. The system could adjust the spark advance, change metering in the carburetor and even open a solenoid to vent the evaporative emissions from the fuel tank.

Branford Public Schools Award $60M Transportation Contract to Zum

Within five years, Zum will transition Branford to a 100% electric school bus fleet, the first in Connecticut.

Tesla Model 3 TPMS Service

Resetting and programming TPMS sensors for a Tesla is a lot like any other vehicle, and the challenge is still the same: keeping the light off.

Can You Jumpstart an EV?

First thing’s first: Find the LV battery, which could be anywhere in the vehicle.

ADAS Module Programming

Reflashing and reprogramming is a necessary service for repairing vehicles.

Other Posts

Mullen Road Tests Solid-State Polymer Battery Pack

The results met or exceeded all requirements targeted for the first drive cycles for energy usage and driving range.

Understanding What Antifreeze/Coolant Actually Does

Today, each manufacturer has its own formula for best results in their vehicles. This video is part of the Group Training Academy.

How The Vehicle Cooling System Functions

Here’s what to know to clarify cooling questions you’re asked at the service counter. This video is part of The Group Training Academy.

Oil Filter Housing Weak Points & Standard® Solutions

Engineers at Standard® have created a completely assembled Oil Filter Housing Kit.