Hey, I've got and 02 2500hd sierra with 180,000 on the dash. The truck has a flashing check engine light with p0300 and lean codes as well as suposedly a bad up stream o2 sensor that normally flashes around 60 mph. However,I can also make it flash while in park when it's rev'ed up to around 2500 rpm. I put all new coils plugs and wires. Ive had to drive it for a month or so the way it is. Doesnt seem to be running rough, cat doesnt seem to get any hotter than normal. Ive had two shops pretty much refuse to do a crankshaft postion relearn. I dont even know if its actually misfiring at all. Any help would be appriciated.
The flashing engine light means there are a significant amount of misfires occurring, but it will also flash if the ECU detects a severe problem that will cause damage to the engine. The P0300 code is for misfires. Take it to another mechanic shop to look at the ignition timing, camshaft positions, as well as the O2 sensor (faulty O2 sensor can cause misfires from inaccurate air-fuel mixture readings); clearly there is a problem.
@razmigb
Do you believe the o2 sensor could ever cause it to run lean enough to cause the cel to flash. Seems extreme. I know these gm trucks are notorious for intake gaskets for leaking, but I don't have a smoke machine at the moment to check, and I think it shows more symptoms of it needing a crank relearn. Changing the fuel filter now, doubt its the problem, but its definitely needs changing. Thanks for the response.
If your lucky, a new O2 will fix you up. However, I have seen this many times. When you have up O2 out, do a pressure check to insure cats are not overly restrictive. Do both sides. If cats good, replace up O2's and do smoke test per Scotty vidy. Should fix you up. Any other codes besides 300, 13x and 16x?
Yea im getting lean codes for both banks
Yea, expected as much. Pull those upstream O2's, check cat differential pressure (if good), new O2's should fix ya up. If not, replace cats and O2's.
I live in a non inspection state, so I'd probably strait pipe it too
Lucky you! It will throw codes but run better! Just bad cat code tho. And if there's a flow issue in cat causing the 300 code, this will clearly resolve it.
Oh, and gotta disclaimer, even if in non-inspection state, still federally illegal.