2001 GMC Yukon Repair Question
2001 GMC Yukon Code P0301 - Intermittent
2001 GMC Yukon 6 cyl All Wheel Drive Automatic 130K miles
I have an intermittent problem that has been driving me nuts. I can sometimes just start the engine and it starts rough ( misfires) or drive up to 50 plus miles with it running smooth, before I receive engine code P0301 - Cylinder #1 misfire. I have replaced the following over the course of 6 months ever since it did not pass emission testing from the service engine soon lamp.
1. Cylinder #1 coil pack.
2. Plug wires had only 15K miles on them, so I swapped out cylinder #1 wires with another cylinder, the trouble did not follow.
3. Replaced both O2 sensors, upstream and downstream on bank one side ( drivers side of engine).
4. Paid to have injector cleaner fed directly into the fuel rails along with a gas tank injector chemical.
Recapping, this is an intermittent problem, maybe 60-70% of the time the engine is driving rough. I have a decent error code scanner that provides lots of information. I can clear the error code and wait for it to come back.
Any ideas before I start going back and re checking / changing all the above again?
Check miss fire history see that cyl #1 is only miss. If the scanner can do a CKP System Variation Learning proceedure then do that. After monitor MAP voltage is it over 4 volts?
Let me know
Yes I checked the codes after driving 100 plus miles today and I had another code P0420 - Catalyst System Efficiency below Threshold - Bank 1 along with the same code I have had all along, Cylinder 1 misfire. My Actron scanner appears not to be able to do a CKP system variation. I see a MAP reading on the scanner but the units are in inches of Hg - 28.9, not in voltage units.
1 question asked
MAP reading good. Thinkcrank and cam are out of sink that was what relearn would have showed. Need to have truck put on a diagnostic scan tool such as MODIS.
420 maybe setting because of 301.
With the MODIS diagnostic scanner, are you stating the scanner will show a loss of signal with a time stamp from either the crank or cam position sensor?
I don't know how GMC designs it on the '01 Denali, but on my other car a '98 Linc Mark Vlll, the cam position sensor can actually fail and still run OK, but not at peak performance (still smooth, not rough) just using the crank position sensor. With the cam sensor not working, the car would never start on the first attempt. It needed more exact timing for fuel injection I believe.
1 question asked
MODIS can preform relearn which is step 1 in diagnostic. will be able to tell if missfire is incremenating which will tell if injector is at fault Also pull vacuum line off pressure regulator see if fuel is present