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I have a 2016 Sierra 1500 with the 5.3L engine, 111k miles. About 6 months ago I changed the spark plugs & wires and one of the wires accidently got pulled out by the stupid long bolt in the steering shaft that run way to close to one of the spark plug wires. The truck misfired but I was only a few miles from home. I limped it back, realized the problem, plugged the wire in and all seemed good. Unfortunately, 10 miles later the check engine light came on again, this time just showing P0420 code (catalyst efficiency below threshold, Bank 1). I changed all (4) of the O2 sensors, but the code came back after 10 miles. I then bit the bullet and changed the drivers side cat with a aftermarket weld-on from rockauto, nope. I then paid a muffler shop to replace the passengers side cat (generic) and fix my sad welding on the drivers side. The light stayed off for about 50 miles this time but as always came back on. I then tried to put a spacer between the 2 rear O2 sensors to pull them out of the exhaust stream, light on after 10 miles. I even tried plugging the old 2 rear o2 sensors in the wiring harness and just zip tying them to the frame so they were breathing fresh oxygen, but still the light! My mechanic is out of ideas and suggesting taking it to the stealership and having them replace both cats again with the OEM setup for @$2000. I have almost zero faith that will solve the problem and that it will just be more money that I don't have going into the trash, and the dealer will just shrug their shoulders. Any other suggestions of things to look at/try before jumping off that cliff? I am a backyard mechanic with just a basic OBD2 reader. I do know that all (4) O2 sensors are putting out voltage, but really don't know how to interpret that data.
I have a 2014 GMC 1500 with a 5.3L. I recently replaced my CATs because I was getting the dreaded P0430 code. SO I put new Magnaflow exhaust systems as well as brand new sensors in it. I got it all in and about a day after I got it all installed I got the same code P04030. I double checked the seals and sensors and looked at the live data and it all looks on the level...the only other thing I can think is that there is a wiring issue with it...the connector on bank 2 sensor 2 looks in order so I'm a little confused as to why I'm still getting this code other than there is a ground or an electrical issue I haven't looked at.
Hi! In April, my Yukon was throwing codes P0172 P0175. Local GMC dealer in Louisiana "fixed", by replacing some sensor. Traveled to PA, codes came back on. Local GMC dealer fixed by replacing BCM, body control module in June. Now my check engine light is back on! Power train Warranty ran out 2-3 weeks ago. Also had extended warranty, which also ran out at 5 years, which was Sept. Code onstar says its throwing now is P0430, all of the codes from I can find are related to exhaust system. My question is are these 3 codes related??? Could this be something they will have to fix under warranty, given it's related and has been worked on several times?
If not, what does this mean? Catalytic converter bad? Help! My husband is being laid off in the next week. So, obviously finances are tight. Yes, obviously itll be fixed regardless, just trying to plan and cut back elsewhere if needed. This has been a great vehicle! As luck has it, trouble starts when warranty runs out.
Really wanting to trade, but waiting on new body
Adding mileage if matters, 91K
I have a 2008 GMC Sierra with the 5.3 liter engine. I hear a rattle coming from the underneath of the truck only at 1000-1500 RPM’s. I checked for loose clips and stuff but I have found nothing. It doenst affect the way the truck runs just the sound. Also, the temperature doesn’t affect the rattle.
I don’t know if you all remember me or not. About a month ago I posted about my Yukon misfiring terribly. I fixed that thanks to your expertise and now I have a couple other small issues.
Number 1. I keep getting a P0430 code. I’m pretty sure the right side cat is bad. When reading the O2 sensors. The graph shows identical readings for the upstream and downstream sensors. I’m pretty much resigned to the idea that I’ll have to replace the cats, and found a new set for a decent price. Still I was wondering if any of you could recommend a good set. I can’t weld, so I’ll need to buy the whole assembly. I (think I) have some time on this because I don’t need another emissions test for over a year, but correct me if I’m wrong and if this problem is actually more urgent than I think it is.
Second, and more importantly, I’ve got a squeaky wheel. I tried to diagnose it, by jacking each wheel off the ground and turning it manually, but nothing happened. I checked the CV joints and brake pads in the front, but after a really bad experience when I was younger I won’t mess with drum brakes, so I don’t know if something is up with one of the rear drums, and the rear axle doesn’t have CV joints. The noise seems to come from the front driver’s side wheel. So, if the CV joints and brakes seem fine does that mean the bearings are going bad? Is replacing them possible without an impact wrench and a hydraulic press? Could I just pack them and hope for the best? I’m going to do a little more trouble shooting and update the thread with any new pertinent info.
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