Annoying Check engine light

[SMonaldo]

I purchased a 2017 Yukon Denali in August of 2024 with 58,000 miles on it. I also got the extended warranty. In September they had to replace the lifters. In February of 2025, the lifters went again. They wound up replacing the engine with a long block. Since then I have been getting a constant check engine light relating to the Fuel management system, The have replaced all the injectors, the high pressure fuel pump, and the fuel rails. The last go around (Friday) they updated the ECM firmware. 30 hours later.....cruising at 55, check engine.

I am lost with any more ideas. All mechanical components have been replaced, aby suggestions? When the light comes on the engine does idle a little rough.

 

[OBSandaNNBS]

I purchased a 2017 Yukon Denali in August of 2024 with 58,000 miles on it. I also got the extended warranty. In September they had to replace the lifters. In February of 2025, the lifters went again. They wound up replacing the engine with a long block. Since then I have been getting a constant check engine light relating to the Fuel management system, The have replaced all the injectors, the high pressure fuel pump, and the fuel rails. The last go around (Friday) they updated the ECM firmware. 30 hours later.....cruising at 55, check engine.

I am lost with any more ideas. All mechanical components have been replaced, aby suggestions? When the light comes on the engine does idle a little rough.

Good thing you got a warranty.
What is the trouble code associated with your CEL?

 

[SMonaldo]

I'll have to get back to you on this...

 

[SMonaldo]

Good thing you got a warranty.
What is the trouble code associated with your CEL?

P219A

 

[Joseph Garcia]

Topical explanation below. If you have, or have access to, a quality bi-directional scanner, you could get to the source of your issue fairly quickly.

The OBD-II code P219A indicates a Bank 1 air/fuel ratio imbalance. This means the engine's air-to-fuel mixture on the bank containing cylinder number one is not balanced. The code can be caused by various issues, including vacuum leaks, faulty oxygen sensors, exhaust leaks, or problems with the fuel system.

Here's a more detailed generic breakdown:

• What it means:
  P219A signifies that the engine's air-fuel ratio on Bank 1 is not being properly controlled, resulting in a lean or rich mixture.
  
  
• Potential causes:
  • Vacuum leaks: Unsealed areas in the intake manifold or engine components can draw in extra air, affecting the air-fuel ratio.
    
    
  • Faulty oxygen sensor: The oxygen sensor is responsible for monitoring exhaust gases and providing feedback to the engine control unit (ECU). A faulty sensor can provide inaccurate readings, leading to an imbalance.
    
    
  • Exhaust leaks: Leaks in the exhaust system, especially around the catalytic converter or before the oxygen sensor, can also affect the air-fuel ratio.
    
    
  • Fuel system problems: Issues with fuel injectors, fuel pressure, or a clogged fuel filter can contribute to an imbalance.
    
    
  • Other potential causes: Problems with the EGR valve, PCV valve, or MAF sensor can also trigger the P219A code.
• Symptoms:
  Besides the Check Engine Light, you might experience reduced fuel efficiency, a rough idle, or a lack of engine performance.
  
  
• Troubleshooting:
  To diagnose the cause, you might need to check for vacuum leaks, inspect the oxygen sensor, and test fuel pressure and injectors.

 

[Doubeleive]

P219A

maybe tell the shop or dealer that is working on it to actually troubleshoot it instead of throwing parts at it, I mean you got a new engine out of it already so that's good but no logical reason to have to replace injectors on a brand new engine.

 

[SMonaldo]

it is going back to the dealer on Wednesday, curious that they have already replaced fuel rails, injectors, and HP fuel pump, and ecm firmware, but have ignored MAF, O2. egr and pcv. Also I have read that a possible faulty fuel pressure regulate could also be a culprit.

 

[SMonaldo]

maybe tell the shop or dealer that is working on it to actually troubleshoot it instead of throwing parts at it, I mean you got a new engine out of it already so that's good but no logical reason to have to replace injectors on a brand new engine.

Supposedly they are working with GM engineering....so they say. I have been over their shoulder while the vehicle has been connected to the computer and besides the code, nothing else indicates what is actually triggering the code

 

[Doubeleive]

Supposedly they are working with GM engineering....so they say. I have been over their shoulder while the vehicle has been connected to the computer and besides the code, nothing else indicates what is actually triggering the code

that's where the troubleshooting part comes in, they need to look at ALL of the external possibilities, starting at the battery, grounds, maf, 02 sensors, possible leaks, backpressure test, etc, etc,
if it was a long block they re-used the intake, so smoke test.
all it takes is something being a little too much out of whack and the code is set
it sounds like it happened or happens under a load so that's going to make it a little harder, someone probably needs to do a drive record and look at all the data.
my guess would be something in the intake or exhaust if not a leak on the intake. but the electrical system needs to be ruled out first which is generally easy.

the good news is it is not likely to be the engine

 

[SMonaldo]

maybe tell the shop or dealer that is working on it to actually troubleshoot it instead of throwing parts at it, I mean you got a new engine out of it already so that's good but no logical reason to have to replace injectors on a brand new engine.

FYI injectors are not part of a long block, so the entire fuel feed system was off the old engine.

 

[SMonaldo]

that's where the troubleshooting part comes in, they need to look at ALL of the external possibilities, starting at the battery, grounds, maf, 02 sensors, possible leaks, backpressure test, etc, etc,
if it was a long block they re-used the intake, so smoke test.
all it takes is something being a little too much out of whack and the code is set
it sounds like it happened or happens under a load so that's going to make it a little harder, someone probably needs to do a drive record and look at all the data.
my guess would be something in the intake or exhaust if not a leak on the intake. but the electrical system needs to be ruled out first which is generally easy.

the good news is it is not likely to be the engine

Oh, I'm with you on this. I am an engineer that works in the IT field, and if I went about the process they are following I would have been fired a long time ago. I have always taught people under me to never shotgun an issue, and that's exactly what they are doing. At this point I am strongly requesting they replace the egr, o2, pcv, maf and fuel pressure regulator. After that they can start doing what you suggest while I drive a rental at their cost. Eventually I will have a new engine and all the components @ 70k miles, and a 3 yr 100K mile warranty on GM. I LOVE THE TRUCK.

 

[Doubeleive]

FYI injectors are not part of a long block, so the entire fuel feed system was off the old engine.

ya, I was thinking of a different engine....
but still, warranty coverage should require verification that the part has failed, just doesn't sound like they are digging very deep.
I guess it depends on the warranty, wish I had deep pockets to replace anything suspect lol

 

[SMonaldo]

maybe tell the shop or dealer that is working on it to actually troubleshoot it instead of throwing parts at it, I mean you got a new engine out of it already so that's good but no logical reason to have to replace injectors on a brand new engine.

update....They finally caved and replaced the bank 1 O2 sensor. That was around the middle or September. The light stayed off for 2 solid weeks, then popped on while on the hgwy. I reset the code the beginning of October, and it was good until this morning's drive to work, also on the hgwy. So now I'm thinking as close as we are, there is another culprit involved. Interesting symptom is while the light is off, the engine purrs like a kitten. As soon as the light come on, I get a rough idle.....cause and effect?

 

[Doubeleive]

update....They finally caved and replaced the bank 1 O2 sensor. That was around the middle or September. The light stayed off for 2 solid weeks, then popped on while on the hgwy. I reset the code the beginning of October, and it was good until this morning's drive to work, also on the hgwy. So now I'm thinking as close as we are, there is another culprit involved. Interesting symptom is while the light is off, the engine purrs like a kitten. As soon as the light come on, I get a rough idle.....cause and effect?

an 02 sensor should not go bad that quickly, I would replace it with a oem or use a denso, which is what would come in the gm box anyway

 

[Fless]

When that code pops up is there freeze frame data for it? If so, investigating the freeze frame PIDs might point to a cause.

 

[SMonaldo]

When that code pops up is there freeze frame data for it? If so, investigating the freeze frame PIDs might point to a cause.

P219A. What are the freeze frame PID's and how do I get them?

 

[SMonaldo]

an 02 sensor should not go bad that quickly, I would replace it with a oem or use a denso, which is what would come in the gm box anyway

My suspicions are that there are multiple causes. We no have a factory rebuilt engine with 8 yr old sensors monitoring the system.....any or all could be off.

 

[Doubeleive]

My suspicions are that there are multiple causes. We no have a factory rebuilt engine with 8 yr old sensors monitoring the system.....any or all could be off.

if they were off the code would not set, if it was a cheap aftermarket 02 sensor, then some aftermarket parts are known to fail in short order.

 

[Fless]

P219A. What are the freeze frame PID's and how do I get them?

Your scanner would need to support freeze frame data for any given PID.

 

[SMonaldo]

Your scanner would need to support freeze frame data for any given PID.

I can do that, but I would have to be running all the time with the scanner connected, not a predictable occurrence nor is it something I know how to trigger...