Need assistance /help in Virginia

[johnnybravo]

Hello all,

Hopefully someone on this forum is willing and can help me with this. I dont know if you are familiar with the dreaded P0300 mistery at 70mph, if not, there is plenty to read on this GM forum as well as many others sites, i say a mistery because like others i coukd not figure it out even after test after test and replacing parts left and right. i muself have done tons of research on this. In a 12 month period i have had this code a total of 8 times, 6 of those times where deliberately done to assure it was only happening on or over 70mph mark and the first 2 times i was taken by surprise but soon realized it happened only at or beyond 70mph so of corse i made sure by purposely hitting that speed once every few month but besides those speeds and times it has never coded any other time in 15 years of owning her. No lose of pressure, no problems at all with power or start ups or idle, does not hesitate, hick up, smoke, or burn to much fuel (other then normal) So this is what i need help with, from my understanding some of you have experienced the same issue and had a crank relearn and it fixed the problem, i need to have this done but the local dealership is giving me attitude and questioning me like i was steeling something, basically they wont do a crank relearn and he (service manager ) looked puzzked as to what it was and why i needes it, he said i neede to get all kids of test done on the computer and would cost big bucks so thats a no go for me.

Is there anybody here that lives in or near VIRGINIA that has a scanner or knows somebody in my area that can do the crank relearn for me, i really need your help with this if you can. This driving like an old lady stuff is killing me, dont get me wrong, i dont race it or anything like that but i have to get on highway everyday and have to stay in slow lane and cant think of trying to pass someone or that light (SES) starts blinking. I have replaced every part you can shake a stick at, everything is new, everything under the hood has new OEM parts with under 5,000 miles on them to include fuel pump, smoke test was negitive, fuel pressure was as should be, oil pressure was fine and has new coolant so thats good to. Truck runs flawlessly, no lack of anything, gets up and goes, ive towed and hauled and light never comes on, i can poud her from light to light with no issues, its only at 70mph and over but even when it comes on and blinks nothing is wrong, i dont lose any speed, dont lose pressure and as soon as i take my foot off the gas and let it go down to 69 it stops blinking , im thinking it has to be a crank relearn needed since it has worked for so many others that had same issure at 70mph and if not , well; it wont hurt anything. Please help, i live in northern va (woodbridge), i need someone that has the proper scan tool and the experience of doing a relearn to take care of this issue for me. If there in maryland or W.V or even within driving distance of a few hours away, i really need this done.

Thanking everyone in advance for your help. If i have pisted this on the wrong place i am sorry, im new and still trying to navigate my way around.

[Jsdirt]

Do you have misfires on cylinders 1 & 6? If not, a relearn probably isn't going to help you.

 

If you want a relearn done, the dealer is the LAST place on earth I'd go, unless you're still under warranty - not likely on a '02. Find ANY local garage - any high end scan tool has this capability.

[johnnybravo]

Hey,

Thanks for reading/repling, wasnt even sure my post made it thru.

As for the misfire....yes,they showed up on scanner but not in terms of lose of pressure or poor idling or anything yhat would sudgest a ptoblem, least nothing found.

Think i found someone that is going to do the relearn for me and if it dosnt work i dont know what else to do from there so im hopeing it takes care of the problem. Its just really weird because theres nothing wrong and all ignition parts are new, all fuel components/parts are new, new updated intake gasket (teal/green), open the hood and anything you can see with your eyes in terms of sensors/parts are all new oem replaced including the fuelpump. I can't figure this out. There are no compression leaks anywhere,have goid compression, all ground wires are fine, fuses/relays all working, real mistery Anyway, thanks for taking intrest.

[Jsdirt]

Some other things that can cause misfires are leaky valves (can be confirmed with a leak-down test), bad lifters or cam lobes, valve springs, extremely worn valve guides, blown head gasket, or worn piston rings. Usually most of these will be cylinder specific, and not random ... unless the vehicle has alot of hard miles on her - in that case anything is possible. Some of these may not show on a regular compression test, and some will only show during running tests.

 

Make sure you don't have any fuel contamination (water, diesel, dirt), and double check fuel pressure (even though you recently changed the pump).

 

If the misfire is happening at 70 mph at LIGHT throttle CRUISE, that suggests there is a vacuum leak somewhere. Full or heavy throttle is a different story - that would point more to spark or fuel delivery (filter, pump).

[johnnybravo]

Motor is spotless, no leaks if any kind, im really not investigateing the cause as im sure its crank related, i just need to gind someone with a scanner or maybe somebody with knowledge of what kind of scanner will work to do a relearn, stealership wants to keep the truck and run all kind of ecu test costing me big money i dont have, service manager said he never heard of crank relearn for the 70mph p0300 even after i showed him over 100 documented fixes from it and also showed him on my laptop people with the same mistery problems with that 70mph flashing ses light that takes most people months if not years to figure out but even with that he wanted me to leave my truck and that just wont happen. I do basic mechanic work, im not a mechanic but have been working on vehicals for over 25 years, i understand misfire and possible causes but this is a computer thing im sure. If you could only see my motor and the xar ive put into it. The engin on my truck is spotless, aside from aging it looks new still, not even dust showing anyplace on the motor. Done fuel pressure test and all fine, oil pressure test and all fine ground wires all intact, clean surface for ground, new coils, new plugs, new wires, new fuel injectors, new fuel pressure regulator/vacuum hose, new pvc/hose, new mass sensor, newidel air control valve, newfuel pump, new map sensor, newknock sensors/harness, new map sensor,new cam sensor, new egr, new intake gasket (green), everything new, OEM and has under 5000 miles on them. Nope this happened after replacing knock sensorsand map sensor, i think by disconnecting these items something triggered and now a crank relearn has to be done, hopefully i will find someobe with a scanner that will do it and if it dont fix it then i got bigger problems, but if it does the trick and im 99.9 percent sure it will i willl let everybody know because this is so common with GM, also, FYI: GM crank sensors had a lot of issue with going bad and not setting off the code but will trigger the p0300 code. Ive done so much researchnon this subject over the last 8 months. Dosnt mean i know for a fact that this is the problem, it just means i did a lot if research and discovered GM motors are prone to these nyster p0300 codes that are not related to leaks of any kind, or bad fuel ir fuelnpump or fuel rail and so on and so on. So for now if anyone coild please let me know what kindsnof scanners will work, inknow HPTunner, EFIlive and tech11 will but will snap-on ir any others do it? Thanks for reading and taking intrest. Sorry for any miss spellings

[Jsdirt]

Like I said before, any high end scan tool has that capability. Autel Maxisys, Snap-On Verus, Tech II, etc..

 

Without a scope on the crank sensor, it's just guessing. No harm in trying a relearn if you can find a garage that will do it cheap. Shouldn't charge more than a half hour labor for that, I would think. It doesn't take long, as long as all the parameters are met (engine temp., mainly).

[johnnybravo]

Yea,

I agree, i havent been driving the truck anyway so theres no rush to get it done but im hopeing to find someone that knows the process, im just really not wanting to leave it with the dealership, so yea, no rush but eventually i will have the relearn done and i will post the results as im sure many will want to know. Again, this isn't a typical p0300 random misfire, typical as in problems with idling or hesitates, loosing power, wont start or anything like that, this is only ses flashing at 70mph and i dont lose power, dont hesitated etc, i believe because i have a bad / slightly bad crank sensor that isnt bad enough to give the correct code therefor not communicating/in sink with tha cam sensor and ecu...hense the flashing light at 70mph only with absolutely no faults in performance, and need calibrating if you will, only a hunch.....we'l see if im on the right track soon enough. These electronics on these vehicles are very sensitive and can get out of calibration very easily. I found a bulletin (GM) that shared someting along those lines and when a read it i thought to myself, ok; wow, so im not crazy and way off track like most have suggested, they hear random misfire and of course start talking basic information regarding possible causes but this is actually misfiring even though thats the code, kind of difficult to explain but im sure your understanding this as you seem knowledgeable.

I really appreciate your interest and folliwing up with me on this and thanks for getting that scanner info to me, this helps me in finding someone now with one and not having to use the dealership. I hope to post an update very soon.

Ttyl

[johnnybravo]

Hey jsdirt,

Forgot to ask, you mentioned "engine temp", so are you saying the trucks motor has to be at a specific temp for the relearn? Can you tell me more.

Thanks.

[Jsdirt]

I remember seeing 158° once - tried to do a relearn, and it said "Procedure aborted - engine temp below 158°", or something to that effect. Not a big deal - just let her run a bit until the temp comes up, and try again.

 

Anything is possible, but normally if there's any kind of fault with the crank sensor, the engine becomes a "crank, no start" problem. Very rarely will you have a running vehicle with any kind of crank sensor fault. Without the crank sensor, the computer will not trigger spark or fuel, since it either doesn't see, or can't make sense of the data its receiving as to where the crankshaft is in it's rotation.

 

EDIT just to clarify, a sensor with glitches (as seen on an oscilloscope) will cause a misfire, but normally it will be at any RPM or speed.

[johnnybravo]

Thanks for that info, so i did find someone that has the snap-on scanner, told me to bring it by sometime next week but after reading what you sent it woukd be best to either A) drop it off the night before so that correct temp can be reached or B) get there really early to give time to cool down.

Also, you mentioned about crank problem/no start; funny you mention this because that is probably the ONLY thing ive noticed with my truck not normal. It would always start on first turn of key on very first start of that day but last few weeks it dosnt anymore, 2nd turn starts right up like normal and every first turn of key throughout the day after that first non start it works fine. Fuel pressure is fine, fuel pump is new as is the fuel filter and relay switch. IDK but come next week i will have the relearn done ($75.00) and we'l see. I can tell you this, if it dosnt fix the problem im really stumpt and out if ideas, there is nothing left, everything has been replaced over the last 12 months (not related to current issue) as ive been home and decieded to do a serious preventive on her and i get all oem parts at cost (no mark up) from the dealership here in my area. Basically its a brand new 2002 at this point. I guess if it dont work i have to start testing everything out from scratch, maybe i missed something but i really dont have any missfires, in fact one time when the light flashes at the 70 mark i punched it hard, it had great excelertion, like new! Strong, strong, strong, not what you would expext from a misfire at all, in fact just the opposite. So wish me luck man, ive spent enough time and money on this thing already and really not looking forward to finding out that there is something behind this mistery 70mph flashing SES light after all. Because with no symptoms to go on iL have to test everything until i figure it out....not fun.

Well, imma go kick back and get ready for the game tonight so guess iL be reaching out next week with the folliw up.

Have a good one, enjoy the weekend.

[johnnybravo]

Oh and another thing i forgot to mention that may be a clue, i took the orginal (123K + miles on it) crank sensor off earlier today and installed a new one (oem) and when i started it up the ses started flashing like crazy, i turn the truck off and tred again and when i started it up same thing so i took it iut put the original one back in and it stopped. So its either the original sensor that flashes as soon as i hit 70 or a new sensor that sets it off as soon as i crank it over.

I wanted the new one in for the relearn so i would have to do it later when its really jot outside, suppose to be near 100 next week here in the north east.

Have any idea on what was going on with what i just explained, again my hunch is it out of calibration but that dosent really explain why a new crank sensor would do that unless thats normal behavior for a new crank sensor installation until it gets relearned.

P.s

Sorry that i have to keep replying to myself trying to connect to you but for some reason im not able to do it any other way, im on my cell and that could be the reason.

[Jsdirt]

Don't worry about the engine temp - they will have to let it cool down, then warm up past 158° anyway. With a good scan tool it literally takes less than a minute to do. The command tells you to peg the throttle to the rev limiter, then the relearn is done.

 

Anytime that sensor is touched, a relearn is normally required, otherwise misfire data will be out of whack. That could be your issue, like you've said. I'd definitely throw that new sensor in first, since you already have it, then go get the relearn done.

 

If that doesn't fix the issue, there's probably a wiring problem somewhere, most likely to the crank sensor. Usually if there's any issues related to the sensor enough to cause a code, you can't perform the relearn procedure. Best way to troubleshoot that is with a scope - you'd probably have to pay extra diagnostic time for that separately from the relearn, depending on the shop.

[johnnybravo]

I agree with what your saying about putting it on first (crank sensor) and as i mentioned in last reply i did actually installed it yesterday but SES started flashing directly after so i put the old one back on because (and maybe you could clear this up for me) i was not sure if having the new one in would hurt anything with that flashing SES and i have to drive maybe 15 miles to that shop this upcoming week. If its ok to drive it like that then imma putting it back on, other wise imma leave the old one in until i dtive it to the shop, let it cool down and install it there....what do you think? Think il hurt anything with the new sensor on causeing the instant SES light to flash and still driving it like that for the 15 miles or so? I dont think it will the more i think of it, just the ECU freaking out right? So yea, im excited to finally get this fixed, its been over a year but inly around 8 flashes of that SES but its been driving me crazy not being able to find the issue even after going through every part of the ignition system, fuel system, electrical system, you namenit and ive more then likely checked and/or replaced it and got nowhere so i started hitting the books, blogs, forums and talking to folks and thats how i came to the assumption that i narrowedbit down to the relearn being needed, you would be surprised how many people with similar trucks and cars to for that matter that have gone a year or more and spent countless hours and dollars trying to get to the bottom of the fake out p0300/random misfire, they had the excact issue where everything was fine and yet at 70mph (all of them same speed) would get the flashing SES so thank god for forums or internet i guess for that matter, without that information posted on several different locations with some posting dated back to 2001, i would be still trying to figure this out. ...well havent fixed anything yet but you get what im saying i hope.

Well enjoy the rest of the weekend jsdirt, appreciate the following up with this , really do. And like i said, soon as i get it done i will let you know if it worked or not.

[Jsdirt]

Not a problem - you enjoy the weekend too.

 

If the truck is actually misfiring, there is a chance of melting the catalytic converter down. Raw fuel and converters don't play well - they get EXTREMELY hot. Glowing.

 

If it's just a little "fishbite" misfire that's tough to feel, then I wouldn't worry about it for a 15 mile trip. If one or 2 cylinders were totally dead & missing constantly, it would be a different story. If the problem is just that it needs a relearn, it might not be missing at all, and just throwing a false light. In that case it will be fine.