Also to help diagnose... upon start up. Assuming the only problem was the TB and everything was functioning. Prior to relearn procedure and right after installing. Would it even go into limp mode... or just not be "correct" idle and air fuel.. if anyone actually knows the answer this will help diagnose.
If no relearn was done on the tb then both actually, iirc it will go into limp mode after due to the tb not being synced and creating improper readings which will cause or should cause an unstable idle... it's been a while since I dealt with tb issues as I do relearns as needed.
Ok im having difficulty getting the relearn to go through .. the check engine doesn't blink? I had codes prior to clearing with reader. ( p0037,p2138,p2122. (See pics)) then after I cleared codes the car started up and reved fone no check engine. Then after two restarts went back into limp mode. Then only one code read, p2138. Hitachi tb. New aftermarket pedal not Dorman but another brand the parts guy said makes good electronics. New alternator. Re did and dialectric greased ground cables from bat to engine block and fender. ... re hooked up pcv pipe to intake.
Ok @Sus Spec gonna need some help now. My brother thinks its a bad ecu. Heres why.. when in limp mode it wants to start in limp mode every time.. remember this has gotten progressively worse /more frequent since it first occurred. .. every time I do a relearn process key on 2 sec off 10 on 2 sec off 10, on off, 10 sec on 3 sec 5 pedal pumps wait 7 sec and hold down till light stops blinking.... when i do that it will start up and rev like normal. Ive been able to drive it for 20 min or 20 feet but it eventually goes back into limp mode. His thinking is that it might be a bad ecu somehow? He is ruling out wiring because when I do the relearn and drive it I can go slow or really romp on it and slam the gears through and its fine and strong.. we figure if it was just wiring that should jolt something and cause limp mode?... when i can only drive it short distances it does seem to happen when shifting more often than random? So I'm wondering if I should do a check of all the wiring to ecu.. if so I would need some help with that. Or does it sound like a bad ecu? If so I'd like to replace with a different year if possible because I'm hearing allot of these issues are with 2002 cars. Im almost considering re wiring everything with slightly thicker/high quality wiring as a winter project I liked the car too much to give up on it.... give me some ideas guys. Thanks. Oh as a side not when I dont get the final pedal pump part of the relearn to work properly. Meaning the light does not blink.. it still seems to "take" and revs right up upon restart....
In my exp I have only done the relearn through the scanner. I used an Autel and it took the first try. I have never even attempted the manual way because I hear its a bitch to work, and it also has to be EXACT timing. If you have any kind of access to a scanner that can relearn, do this first. Make sure you doo any and all relearn procedures for the tb and app. If you have to go to Nissan to get it done do it. If it doesnt work otherwise, you will have to check voltages and go thru the procedures as mentioned. It can be at times difficult to condemn an ecu. Its also hard because Im not there to look at it with my own eyes. Try and prove the problem. I still think you should be looking at the pedal rather than the tb. The last bit sounds like it doesnt take.
Do not waste your time upgrading the wire harness. A thicker wire will not do anything except cause you headaches and has a massive chance of connections not being right or crossed. Thats a bigass job that is extremely time consuming. Its just not needed. Also I dont think you can use any other ecu besides an 02-03 unless you convert to 04-06. Also a $1000 upgrade that is not needed.
The way to check for a broken wire is to check resistance between pin out of the ecu, to the pin of whatever sensor you are testing witha good multimeter. Straight wire, no power. Unplug the ecu and really take a look for any corrosion or obviously loose pins. Check any big connectors under engine bay. Burnt connector pins do happen, but should be obvious.
Unfortunately this job sounds like its in depth. Still a possible ecu. Hope this helps.
Thank you... my brother is in agreeable that its hard to condemn an ecu especially when its communicating with scanner and giving voltage readouts for pedals and stuff... i might consult a dealer. I just feel like it's strange that the car randomly goes into limp mode and when it started it got worse over time i can't understand how that would have to do with a relearn? Especially since it runs great after a successfull manual relearn. I may be mistaken but I would assume the relearn is for "fine tuning" and a factory car would run with a baseline... thanks for all your thoughts inreally appreciate it.. id almost rather check all the wires for continuity before replacing ecu.. because there are so many stories of this limp mode thing and all the parts being discussed working for a while till it goes into limp mode eventually.. sounds like faulty wiring to me since its so common of a problem and so hard to track cause almost has to be a manufacture default in wirirng design or quality in my thought process.
Just out of curiocity if I was to change to an 04-06 ecu... it needs a different pedalcorrect? Is that because the plug in is different? Also isn't the throttle body different that it has two plugs instead of one?
You have to find exact specs for voltages. It can still swing thru voltage but may be skewed in some way out of spec. It may cut out randomly. Must check all values and its the best way to diag whats going on by direct evidence and/or intuition, but I know its hard to find these specs if you dont have access to it. Identifix is a great tool if ur bro has an account. A scanner will show you a value of 0 or something way out of spec if theres a problem
A relearn is not a fine tuning. Its a process that many parts require nowadays. Its more of an awakening and and quick adaption to the car. You would think that all specs are the same by factory for whetever car, but a relearn is best when paired to a specific car with its specific specs. Its stupid sometimes really.
02 to 04 conversion involves alot more. Look at 2j's conversion kit.