2004 GMC Yukon Denali XL 6.0 V8
#21
Senior Member
You need a scanner to do a few things. Your PCM may be having problems.
#23
Senior Member
What are the misfire counts on the scanner? If you don't have that PID you need a better scanner.
#24
Junior Member
Posts like a Ricer Type-R
Thread Starter
Yes. Cylinder 2 was max at 21. Cylinder 6 was max at 23. Cylinder 8 didn’t go over 5. All of the other cylinders were at 0. Keep in mind this was live action when car was idle. We changed the ignition coil but still had the same reading.
#25
Senior Member
Do a running compression test.
Also, if that is fine see if you can get the PCM flashed.
Also, if that is fine see if you can get the PCM flashed.
Last edited by carfixer007; 05-21-2022 at 11:06 PM.
#26
Senior Member
True Car Nut
I've seen P0300 on my Yukon (with no individual cylinder codes) when the fuel pump was getting weak and the pressure was marginally low.
What is the fuel pressure?
What is the fuel pressure?
Last edited by CathedralCub; 05-23-2022 at 12:42 AM. Reason: Added the part in parenthesis
#27
Senior Member
If fuel trims are high then yes to fuel pressure being low.
#28
Retired
I agree with CC, if fuel pressure is getting low, this will cause P0300 typically at higher engine load. You probably won't see/feel any misfire at idle. Get it out on the road into its highest gear at a low RPM with the TCC locked up. Gently ease into the gas without the TCC unlocking. If you feel bucking/sputtering etc, then you are misfiring probably due to insufficient fuel pressure.
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#29
Senior Member
I agree with CC, if fuel pressure is getting low, this will cause P0300 typically at higher engine load. You probably won't see/feel any misfire at idle. Get it out on the road into its highest gear at a low RPM with the TCC locked up. Gently ease into the gas without the TCC unlocking. If you feel bucking/sputtering etc, then you are misfiring probably due to insufficient fuel pressure.
#30
Retired
Knock sensors are sensitive enough to detect it, but the human butt dyno probably will not. Thus why I instructed the test as I did.
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