2008 GMC Yukon: check engine light

Filed Apr 29, 2025 · Engine · NY

I purchased a MagnaFlow aftermarket catalytic converter system for my 2008 GMC Yukon SLT 5.3L through Walmart’s online marketplace, sold by a third-party vendor called OurDealsRock. The product was advertised as “50-state legal” and compatible with vehicles registered in New York State. However, shortly after installation, my check engine light turned on, and diagnostic codes P0420 and P0430 (Catalyst System Efficiency Below Threshold) appeared. Initially, I thought this was a minor sensor issue, but over time, the vehicle’s performance gradually deteriorated. I noticed reduced acceleration, poor fuel economy, and eventually significant loss of power. The vehicle began shaking under load, misfiring, and overheating. These symptoms worsened steadily—not immediately—but progressively after continued driving with the aftermarket converter installed. I had the vehicle inspected by a certified mechanic, who confirmed that the MagnaFlow converter was not CARB-compliant, was not approved for use in New York, and that it had been illegally marketed as such. He also informed me that prolonged use of a non-compliant, malfunctioning converter caused excessive backpressure, leading to complete engine failure over time. The diagnosis was confirmed by a second mechanic before I committed to the engine replacement. The product was later removed from Walmart’s site, becoming unavailable for sale in my zip code [XXX] ) shortly after my initial complaint. This shows clear acknowledgment that it should never have been sold to a New York consumer in the first place. But by the time it was taken down, the damage had already been done. Component/system that failed: •MagnaFlow aftermarket catalytic converter system •Ultimately caused failure of the vehicle’s engine block Safety concerns: •My family and I were unknowingly driving with a damaged and failing engine •The vehicle’s degraded performance, overheating, and power loss could have compromised our safety during highway d INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORM

Filed Oct 4, 2023 · Engine, Fuel system · WI

When beginning to drive forward after coming to a stop at an intersection. The vehicle will often stall in the middle of the intersection. Requiring me to switch it transmission into natural and restart it as it’s rolling. I almost gotten rear ended many times I always get honked at. It just a matter of time before it causes an accident. It sometime happens after turning as well. I looked at forums on this gmc Yukon hybrid. And it looks like many other owners are asking the same question and nobody is coming up with any answers. Other customers say the dealer told them the hesitation is Normal. I took my truck into a local repair shop and he called me after three weeks saying it was done, but it still had the check engine light on and still is stalling out in intersections. Charge me $2000. This has been happening daily since I got the vehicle

Filed Nov 26, 2018 · Driver assistance, Electrical · 118,000 miles · WA

While we are driving on a freeway the car suddenly stop and will have a "stability lose control" message on a dash board. The car will stop momentarily and then it will run again after we start the car. The car has no power at all once it stopped. It happens a lot so right now we're not using it due to safety issue. A big safety issue because we use this to travel with family. I brought this to the mechanic but they don't seem to find what's wrong with it. They did a diagnostic test but they did not get an error message at all. Engine light is not even on.

Filed Oct 3, 2018 · Driver assistance, Engine · 134,000 miles · AZ

I have a 2008 gmc yukon slt that I bought in feb of 2015 with 94,000 miles. I have serviced it regularly from day 1 and even paid it off in 2.5 years. As soon as I paid it off, the very next month, my engine started making a weird noise once in a while w/ no check engine light so no one could tell what was wrong. At that same time my "service stabilitrak/service traction control" would ding about 40 times in a row. I serviced the 2 and it did not help for more than 2 days and it started again. This time the check engine light came on codes were for new plugs and fuel filter. Still didn't help. Then my engine blew! Got that replaced and it still to this day is doing same thing! So, like the 330 others, we have a major safety issue that no one cares to address, and I'm done trying! If this man are having the same issue it's a gm issue! I'm copying the federal safety agency and my atty general for help. Please click this link and read 330 complaints about the same exact thing and youtube has people actually stuck bc their car died. Mine did not ever die but it sure feels like it is and . It happens every single time I drive my yukon! Please help us! I'm on unemployment and cannot afford anymore repairs. I shouldn't have to pay for this many things to be fixed and still not touch the problem! [xxx] parts of this document have been redacted to protect personally identifiable information pursuant to the freedom of information act (foia), 5 u.s.c. 552(b)(6).

Filed Jul 9, 2016 · Driver assistance, Engine · 94,000 miles · AR

I'm driving and all of the sudden the stability and traction controls lights start flashing, the check engine light comes on and it goes into 1st gear and won't shift out. It takes about 15 seconds to go from driving 60 miles and air down to 10. Gmc had it a total of 7 weeks in the winter of 2015/2016 and couldn't find the problem. Doing it again now7/7/2016. Took it to another dealer. They think it's a wiring problem but can't find it either. Told me would just have to drive it till it gets worse. I noticed this last time it messed up that it had been shifting very hard that day. Very frustrating to pay that much for a vehicle you don't feel safe driving. Ready to trade but not sure I have much faith in gm vehicles after all the problems I've been reading about.

Filed Apr 1, 2015 · Driver assistance, Electrical · 108,730 miles · AR

While traveling on the interstate at speed (70) the stabilitrac light came on and reduced engine power message displayed. The RPM's went over 4k, then the yukon slowed in traffic and I had to pull to the side before being run over. The accelerator was unresponsive at that time. I turned off the engine, waited about 5 minutes and then resumed driving using '3' to engage transmission instead of 'd' the check engine light remained on, but I made it to my destination 2 hours away.

Filed Aug 25, 2008 · Electrical · 5,000 miles · FL

I have had multiple problems with my 2008 gmc yukon. It first started with my radio cutting on and off. I have been to the dealer 3 times and they can't reproduce the problem. I have had the warning light come on alerting me that I have an open hood, unloosen fuel cap,and the engine light has come on and remained on for several days. Lately the alarm has been going off 5 times to date. I have notified the dealer but I don't feel that it is getting me anywhere. I have delivered it to them three times and have had them check it out twice. Today was the third time and they told me they didn't have a loaner car and to return on wed. 8.27.08 . They did not write up that I was there today. I don't know what to expect the next time a dummy light goes off I only hope that it isn't something serious since all the issues seem to be a "boy crying wolf".