Codes code P0521 and P0521, engine running rough, service Stabilitrak

ALFOWL

MEMBER
2009 CHEVROLET TAHOE
4WD
AUTOMATIC
75,000 MILES

SUV listed above is an LT model, which started running rough a few days ago. Check engine light flashing, dash reading service traction control and service stabilitrak. Computer gave code P0304, misfire in cylinder four. So, we changed the spark plugs which seemed to fix the issue, but very briefly. Again, running rough, engine light flashing and service stabilitrak. Again, gave the same code. So, we replaced the ignition coil in cylinder four. Did not fix issue, computer still throwing code P0304, and now also giving code P0521- Engine Oil Pressure Sensor/Switch Range/Performance. Any ideas as to what could be causing these issues?

2 Replies

ALFOWL

MEMBER
4 POSTS

I should add, we changed the plugs and wires.

Was this

answer

helpful?

Yes

No

Friday, June 10th, 2022 AT 12:21 PM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

I'm not sure how the oil pressure sensor and a cylinder 4 misfire are related. However, if the fuel injector is stuck and flooding that cylinder, it could allow fuel to mix into the engine oil, thinning it and causing low pressure. Do you hear any ticking or knocking when it's running?

Do me a favor. Check to see if the engine oil is full. Also, see if it has a fuel smell to it.

Let me know the engine size. Is it a 5.3 or 6.0L?

The thing is this. If we have fuel and the cylinder 4 is getting spark, then we may need to check compression on that cylinder to see if it is low. However, since the check engine light was flashing, I don't think that is the issue.

One last thing. Let me know if you have a scanner that can provide live data.

Let me know.

Take care,

Joe