Diagnose P219A P219B P0300

Caleb Simonds · May 9

Recently I had my lifters collapse and i brought it to a shop and they put a new motor in it with the AFM/Dod delete. Ever since I’ve had a check engine light for P219A P219B PO300 that I can’t figure out. It drives fine but at idle it has a rough shake. The truck has new coils,wires,plugs. New injectors New 02 sensors New high pressure fuel pump. New exhaust manifold gaskets. I cleaned the maf sensor and throttle body. I sprayed brake clean around the intake gaskets and there was no change in idle. I did a compression test and cylinders 1,4,6,7 have 180 psi and 2,3,5,8 have 210 is this normal? Any information helps.

davester · May 9

why are you not driving back to the shop to get it working right? this shouldn't be on you at all (other than perhaps if you bought the engine, drove there and just paid them to put it in, then you tuned it yourself or something like that).

anyway, I can only suggest working through the diagnostic procedures for those codes, found on alldata.com (needs subscription).

davester · May 9

Actually, you should be able to also use this site: https://lemon-manuals.la/

Caleb Simonds · May 9

8 hours ago, davester said:

why are you not driving back to the shop to get it working right? this shouldn't be on you at all (other than perhaps if you bought the engine, drove there and just paid them to put it in, then you tuned it yourself or something like that).

anyway, I can only suggest working through the diagnostic procedures for those codes, found on alldata.com (needs subscription).

I have brought it back to them multiple times each time they can’t figure it out or they tell me it’s fixed but when I pick it up it’s still not fixed. I picked it up without check engine light (still running rough) and 5 miles down the road it comes back on. The last time they looked at it they said that the issue was the 02 sensors were not OE so I brought it to a dealer to put OE 02 sensor in it and they said my 02 sensors are fine and the dealer wrote

scanned codes and it has codes for p219a and p219b fuel trim cylinder balance both banks, watching misfires it is misfiring on cylinders 1,4,6,7 which are all AFM cylinders, looked at AFM data and everything is reading malfunction which is what is disabling the injectors for 1,4,6,7 causing the cylinder balance codes, customer stated the truck has an afm delete kit, either there is a problem with the delete kit or the tuning because the delete kit is causing the injectors to shut off. i brought this up to the shop that did the motor and they said they don’t know how this is possible. I had a tuner come out to confirm the tuning was correct and it is. Sorry for the small text I’m not sure how that happened.

Caleb Simonds · May 9

8 hours ago, davester said:

Actually, you should be able to also use this site: https://lemon-manuals.la/

What does this site do?

newdude · May 9

44 minutes ago, Caleb Simonds said:

I have brought it back to them multiple times each time they can’t figure it out or they tell me it’s fixed but when I pick it up it’s still not fixed. I picked it up without check engine light (still running rough) and 5 miles down the road it comes back on. The last time they looked at it they said that the issue was the 02 sensors were not OE so I brought it to a dealer to put OE 02 sensor in it and they said my 02 sensors are fine and the dealer wrote

scanned codes and it has codes for p219a and p219b fuel trim cylinder balance both banks, watching misfires it is misfiring on cylinders 1,4,6,7 which are all AFM cylinders, looked at AFM data and everything is reading malfunction which is what is disabling the injectors for 1,4,6,7 causing the cylinder balance codes, customer stated the truck has an afm delete kit, either there is a problem with the delete kit or the tuning because the delete kit is causing the injectors to shut off. i brought this up to the shop that did the motor and they said they don’t know how this is possible. I had a tuner come out to confirm the tuning was correct and it is. Sorry for the small text I’m not sure how that happened.

Do you have 4 OEM oxygen sensors installed? GM vehicles DO NOT like ANY aftermarket O2 sensors. Needs to be OEM only. Don't even use ones that say they are the OE sensor. Needs to be the genuine GM OEM ones. Seen way too many issues with this. One of the leading causes of P219A and P219B is aftermarket oxygen sensors pre catalyst.

Also. What fuel injectors were installed? GM OEM? Aftermarket? All all 8 injectors matching spec and p/n?

Edited May 9 by newdude

Caleb Simonds · May 9

1 hour ago, newdude said:

Do you have 4 OEM oxygen sensors installed? GM vehicles DO NOT like ANY aftermarket O2 sensors. Needs to be OEM only. Don't even use ones that say they are the OE sensor. Needs to be the genuine GM OEM ones. Seen way too many issues with this. One of the leading causes of P219A and P219B is aftermarket oxygen sensors pre catalyst.

Also. What fuel injectors were installed? GM OEM? Aftermarket? All all 8 injectors matching spec and p/n?

No the genuine gm oem are not in it. They were TRQ OSA61839. And the injectors I got from advanced auto brand car quest. The shop was concerned about that and replaced the injector on the cylinder that was showing misfire with an oem one and there was no change. I realize now after putting the parts in that I should have went oem.

Caleb Simonds · May 9

2 hours ago, newdude said:

Do you have 4 OEM oxygen sensors installed? GM vehicles DO NOT like ANY aftermarket O2 sensors. Needs to be OEM only. Don't even use ones that say they are the OE sensor. Needs to be the genuine GM OEM ones. Seen way too many issues with this. One of the leading causes of P219A and P219B is aftermarket oxygen sensors pre catalyst.

Also. What fuel injectors were installed? GM OEM? Aftermarket? All all 8 injectors matching spec and p/n?

Do you recommend me getting Acdelco 02 sensors or what sensor do you recommend?

newdude · May 11

On 5/9/2026 at 11:48 AM, Caleb Simonds said:

No the genuine gm oem are not in it. They were TRQ OSA61839. And the injectors I got from advanced auto brand car quest. The shop was concerned about that and replaced the injector on the cylinder that was showing misfire with an oem one and there was no change. I realize now after putting the parts in that I should have went oem.

On 5/9/2026 at 1:01 PM, Caleb Simonds said:

Do you recommend me getting Acdelco 02 sensors or what sensor do you recommend?

As I already pointed out in my original reply...OEM and OEM ONLY for the oxygen sensors.

Install 4 original equipment oxygen sensors, and then see where it ends up from there.

Get them at the dealer, a local ACDelco store, or from GM's official parts portal - Shop GM Genuine Parts & ACDelco Parts | GM Parts Store

eBay and Amazon will often have parts that "look" the part (no pun intended) but are often counterfeit.

Edited May 11 by newdude

carkhz316 · May 11

On 5/9/2026 at 9:19 AM, newdude said:

Do you have 4 OEM oxygen sensors installed? GM vehicles DO NOT like ANY aftermarket O2 sensors. Needs to be OEM only. Don't even use ones that say they are the OE sensor. Needs to be the genuine GM OEM ones. Seen way too many issues with this. One of the leading causes of P219A and P219B is aftermarket oxygen sensors pre catalyst.

Gosh is this certainly true. I've wasted a bit of time with aftermarket sensors causing repeat and new o2-related DTCs. I've had multiple Denso sensors cause faults. The worst part is some of the GM sensors are made by Denso, but I guess the quality control varies between their own and contract parts.