hello my name is XXXXX XXXXX have a question was the vehicle warmed up when this happens
Customer: It usually starts flashing after we drive 2 miles. Anytime we keep the rpms at approx. 1500 at 45mph it will start. Usually takes 10 miles off this going off and on to set. Sometimes it may take a few days to set the code.
interesting that would explain the coolant temp
ok sorry i type slowly
ok how is your maintainance you said it was sludged so do you change the oil regularly?
Customer: Yes, in the past we waited for the oil change light to come on. Now we do it every 5k since the flush
well it is starting to sound like your EGR valve is sticking
Customer: So that would explain why this only happens at 1500rpm. Driving the car now and just set the code again. Do you need that freeze frame reading
Customer: New freeze:
Customer: fuel sys1 cl, using h02s
Customer: fuel sys2 n/a
Customer: calc load 48.2
Customer: coolant 90
Customer: st ftrm18.1
Customer: lt ftrm1 0.7
Customer: map (kpa) 65
Customer: engine rpm 1576
Customer: veh speed km/h 72
Customer: ign adv (deg) 31.0
the freeze frame narrows a little it could also be clogged injectors or a vacuum leak but being that it only happens at 1500 rpm i would tend to think its carbon deposits in the EGR system i would try cleaning the carbon out with a little carb cleaner and a toothbrush and put it back to see if it helps first
Customer: iat 17
Customer: maf 19.5
Customer: abslt GPS 29.8
Customer: Ok. I'm going try this tomorrow. If this doesn't work. Any other thoughts?
give me a min to think
if you had a oscilloscope you could test the secondary ignition system, the gap on the plugs could be off. causing it but it would be unusual in such a narrow rpm range i am really wanting to say its carbon buildup
Customer: Cool. Peobably do this tonight. Thanks again
my best advice is to perform an air induction cleaning, and clean or replace the EGR and see, past that
its going to take some research
glad to help if you need any further help dont be afraid to ask
Customer: Bad news. No egr on a hummer. System has a vvt.