Cold Start Rough Idle How to Diagnose Trouble Codes P050D P219A

Here we have a 2017 GMC Yukon XL with a check engine light. The codes that we have are a P050D and also a P219A. In this video, we're gonna go over what those codes mean and what to look for.

Let's go over these codes first. We scan tested the vehicle, pulled up the codes. The first code, Cold Start Rough Idle, is exactly what it sounds like. When you start the vehicle and it's cold, the engine hasn't warmed up yet, the engine runs rough. The most likely cause for an engine running rough is a misfire. So we're gonna have to look into that. The second code that we have is the Fuel Trim Cylinder Balance Bank One Malfunction. Because this is a V8 engine, you have two banks, you have bank one and bank two. The problem is with bank one and it has to do with the fuel delivery system. There's either too much fuel or too little fuel, and the computer's picking up on it, that's why you get the code.

There is some common problems on these vehicles that could relate to either one of those codes, the carbon buildup on the valve, which you have to do a decarbon, and that explains why the vehicle would start and you get a cold misfire, once it warms up that carbon's not as much of an issue. So, a decarboning or a top engine clean would take care of that problem.

With the fuel trim code, there is common problems with fuel injectors failing. So it could be either one of those or they could be related, but we're gonna do some simple tests before we assume it's either one of those. While we're scan testing the vehicle, we can look at the misfire counts and see if there's any misfires. Right now we don't really see anything, the engine's starting to warm up a little bit, but if we look at cylinder three misfire count, we've got over 2300 misfires on cylinder three. If I rev the engine a little bit and let off, once in a while I can get a misfire on cylinder three. Yeah. So it's pretty steady on cylinder three, when I try to manipulate this. It'd be better if we had a constant misfire on one of these cylinders, then it'd be easier to narrow it down, but we'll still do some other tests.

So the fuel trim issue was on bank one and cylinder three is on bank one. Cylinder three is the second one back, where this wire is. So that's the spark plug wire that goes to cylinder three. Now, if you assumed that it was a fuel injector, what you could do is swap the injectors and see if the misfire moves. Because this is direct injection, it's underneath the intake, it's not that easy to do. An easier thing to do would be swap one of the wires, the plugs and the coil, and see if you can get the misfire to move, so that's what we're gonna do.

The coils that I swapped was cylinder three, so this is where our problem was. So, cylinder three and five. So, if the misfire moves to five, we know it's a bad coil. And with the plug in the wire, I moved those to cylinder one. So, if it moves to one, it's either the plug or the wire. Checking the misfires again, the misfire stayed with cylinder three, so it's not the coil, it's not the plug or the wire. So we narrowed it down. We know it has nothing to do with the ignition system. Most likely it's carbon buildup on the valves. We don't have a proper way to clean the valves here. So, we're gonna have to bring this vehicle to a dealer. Then if there's a problem with the injector and it's under the special policy, they can fix it as well.

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