2005 GMC Envoy

The 4.2L LL8 Atlas inline-6 engine develops severe timing chain stretch and guide failure. The primary and secondary timing chain guides crack, break apart, and send plastic debris into the oil pan. Symptoms include a loud rattling noise on startup that may persist, check engine lights with timing codes, and rough running. Complete guide disintegration can cause the chain to skip teeth, destroying the engine.

Replace all timing chains, tensioners, and guides as a complete set. This is a major repair requiring significant engine disassembly. Use updated GM guide parts with improved materials. Flush the oil pan and pickup tube screen to remove plastic debris. Maintain strict oil change intervals with quality synthetic oil to extend the life of the replacement parts.

The HVAC blend door actuators fail frequently on the GMT360 platform, producing a repetitive clicking or knocking noise from behind the dashboard. The actuator gears strip and the blend door gets stuck, causing the system to blow only hot or only cold air regardless of the temperature setting. The noise is particularly annoying as it occurs every time the ignition is turned on.

Replace the failed HVAC blend door actuator. The Envoy has multiple actuators controlling temperature, mode, and recirculation doors. The driver-side temperature actuator is the most common failure. Accessing the actuators requires partial dashboard disassembly. Use AC Delco replacement actuators for proper fit and function.

The Envoy is plagued by various electrical issues including intermittent gauge failures where the speedometer, tachometer, or fuel gauge stop working or read incorrectly. The instrument cluster stepper motors fail, causing the gauge needles to stick or read zero. Other electrical issues include power window failures, door lock malfunctions, and intermittent no-start conditions.

Replace or rebuild the instrument cluster. Cluster repair services are available that replace all stepper motors and re-solder the circuit board for $100-$200. For power window issues, replace the window regulator and motor assembly. For no-start conditions, inspect and clean the battery cables and ground connections, particularly the engine-to-chassis ground strap.

The engine cooling fan clutch fails, either locking up (causing excessive noise and drag) or freewheeling (causing overheating). A failed fan clutch that does not engage properly allows the engine to overheat in slow traffic and during towing. The 4.2L inline-6 runs hot under load, making a functioning fan clutch critical. Owners report overheating warnings during summer driving.

Replace the fan clutch assembly. A locked-up fan clutch will cause a loud roaring noise and reduced fuel economy. A freewheeling clutch will not cool adequately at idle or low speeds. Also inspect the radiator for clogging or corrosion, the thermostat for proper operation, and the coolant level and condition.

The front differential and transfer case develop fluid leaks from the output shaft seals, pinion seals, and case halves. Low fluid levels in either component can cause gear damage, bearing failure, and eventual loss of four-wheel drive function. Owners notice fluid spots under the front of the vehicle and may hear grinding or whining noises from the drivetrain when 4WD is engaged.

Replace the leaking seals and top off or replace the fluid in the front differential and transfer case. If the components have been run with low fluid, inspect the gears and bearings for damage. The transfer case encoder motor and front axle disconnect actuator should also be inspected, as they are common failure points on the GMT360 platform.

CERTAIN MAXZONE HEADLIGHT ASSEMBLIES, DEPO BRAND, P/NO 335-1120L-AS, SOLD FOR USE AS AFTERMARKET EQUIPMENT FOR THE ABOVE LISTED PASSENGER VEHICLES. DURING PRODUCTION THE LAMP HOUSING SHAPE DEFORMED DISTORTING THE ASSEMBLY ANGLE OF THE REFLECTOR AND INFLUENCED THE AIMING POSITION. THESE HEADLAMPS FAIL TO CONFORM TO THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 108, LAMPS, REFLECTIVE DEVICES, AND ASSOCIATED EQUIPMENT.

DECREASED LIGHTING VISIBILITY MAY RESULT IN A VEHICLE CRASH.

MAXZONE WILL NOTIFY OWNERS AND OFFER REIMBURSEMENT FOR ANY NONCOMPLIANT HEADLIGHTS. THE RECALL BEGAN ON FEBRUARY 16, 2007. OWNERS MAY CONTACT MAXZONE AT 909-822-3288.

CERTAIN VEHICLES ORIGINALLY BUILT WITH CLOTH SEATS THAT WERE EQUIPPED WITH AN AUTOMATIC AIR BAG PASSENGER SENSING SYSTEM AND LATER REUPHOLSTERED WITH AFTERMARKET LEATHER SEAT COVER KITS ARE INVOLVED. TESTING HAS INDICATED THAT THE AFTERMARKET LEATHER SEAT COVERS CAN CAUSE THE PASSENGER SENSING SYSTEM TO MALFUNCTION.

IF THE PASSENGER SENSING SYSTEM MALFUNCTIONS, THE FRONT AIR BAG ON THE PASSENGER SIDE MAY BE DISABLED WHEN IT SHOULD BE ENABLED, OR ENABLED WHEN IT SHOULD BE DISABLED. IN EITHER CASE, IN THE EVENT OF A CRASH THAT REQUIRES AIR BAG DEPLOYMENT, A FRONT PASSENGER'S LEVEL OF INJURY MAY BE INCREASED.

BECAUSE A REPLACEMENT LEATHER SEAT COVER THAT IS COMPATIBLE WITH THE PASSENGER SENSING SYSTEM IS NOT AVAILABLE, GENERAL MOTORS (GM) WILL REPURCHASE THESE VEHICLES IN ACCORDANCE WITH THE TERMS STATED IN GM'S LETTER TO OWNERS. THE RECALL BEGAN ON NOVEMBER 6, 2006. OWNERS SHOULD CONTACT GM AT 1-877-477-1022 TO BEGIN THE PROCESS OF REPURCHASING THEIR VEHICLE.

CERTAIN SPORT UTILITY VEHICLES FAIL TO COMPLY WITH THE REQUIREMENTS OF FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 212, 'WINDSHIELD MOUNTING.' THE WINDSHIELD URETHANE BEAD MAY NOT HAVE ADHERED TO THE BODY IN CERTAIN AREAS DURING THE CURE PROCESS.

IF A CRASH OCCURS, THE WINDSHIELD MAY NOT BE RETAINED, INCREASING THE RISK OF INJURY TO A VEHICLE OCCUPANT.

DEALERS WILL REPLACE THE WINDSHIELD FREE OF CHARGE. THE RECALL BEGAN ON MARCH 10, 2005. OWNERS MAY CONTACT BUICK AT 1-866-608-8080, CHEVROLET AT 1-800-630-2438, OR GMC AT 1-866-996-9463.