A big thing we’ve seen a lot of over the past year or so, has been timing chain problems on the Chevy Traverse, Saturn Outlook, GMC Acadia, and Buick Enclave. All of these SUV’s have the 3.6 liter V6 engine with dual overhead cams. What is happening on these vehicles is that the timing chains are stretching which leads to correlation errors with the cam sensors and actuators.
Usually we see this only on 2007-2009 model year vehicles. After 2010, General Motors has seemed to correct the problem with updated chains and ECM calibrations.
This was first thought to be caused by lack of oil changes, and there was a recall to update the vehicle’s computer to shorten the oil life monitor. This was supposed to get customers in sooner to change their oil, thus hopefully eliminating sludge build up, heat, and excess wear and tear that leads to the chains actually stretching some.
On the older models, this didn’t seem to matter. They would still be coming in with the check engine light on and usually running rough. There would most times be trouble codes for cam sensor/actuator correlation, usually on bank 1. Something like a p0017 and a P0008 would definitely mean the engine has stretched chains. Now, this is no small job!! The entire engine and transmission has to come out on a lift table. This requires much work, just even disconnecting all the wiring harnesses and sensors. The air conditioning system has to be recovered and lines removed from the compressor. The trans cooler lines and power steering cooler lines have to be disconnected. The shift linkage, complete engine harness, upper and lower radiator hoses, and fuse box just all come out just to name a few.
Then, once the engine is out and accessible, the real work begins! After removal of the valve covers, intake manifold, power steering pump, belt, tensioner, water pump pulley, alternator and crank pulley, the aluminum front cover can come off. There are quite a few bolts that hold it on and they all have a small rubber seal that goes on each bolt. Now, finally, you can access the actual timing chains where the problem lies.
Once you can get your hands on the chains, you can easily feel the excessive play in the chain from being too far stretched out. This leads to the timing being off, setting the check engine light on, and usually a rough idle. There are three different chains that will require replacement with the updated parts. There is also some special tools needed, such as camshaft holding tools, etc, that are needed to do this job.
The chains, guides, hydraulic tensioners can all be taken off and the chains removed. Now the engine can be placed at top dead center and the holding fixtures installed on the cams once the timing marks are lined up on the crank gear and oil pump cover. The left chain goes in first, following the timing procedure, then the primary chain, then finally the right side cam chain. Once all the chains have been installed, and their guides and tensioners, the process of putting it all back together can begin. Let’s just say this is NOT a job for the backyard mechanic. It will take even the most experienced technicians the better part of a whole day to do this job, sometimes longer.
Luckily for most customers, the powertrain warranty covers this repair up to 100,000 miles. Otherwise it would be very expensive to repair. So, if you’re having these symptoms, don’t wait another minute to go in to your dealership and get this checked out!
Below are two pictures so you can see just how involved this job is. The first pic is of the entire engine/trans assembly out of the Traverse and ready to disassemble. The second pic is a close up of the three timing chains that will be replaced. You can see there are quite a few sprockets, and things to go around!