stc876

Hey my 97 prelude went in to limp mode last month so i pulled my ecu codes it came up with knock sensor, primary o2 and secoundary o2, I replaced all these sensors the car was still in limp mode so i pulled the cel again it came up code 0 or bad ecu. so i ordered a obd 1 ecu with a conversion harness. i plugged in my obd 1 ecu and the car was still in limp mode so i pulled the code again it came up as code 9 or cyp sensor. so i did some digging and my cyp was fine but my ckp had been frayed by the alternator belt so i bought an obd1 distributor which has the cyp, ckp and tdc sensor inside of it vs the stock set up with the ckp and tdc behind the oil pump. so i put the new dizzy on again the car was still in limp mode i pulled the cel for the four the time and it says code 0 again or bad ecu.......

basicly what im wondering is could the frayed wire to my ckp/tdc ruined my new ecu if so how can i check. and if not thouse sensors what are reason a car could repeatedly burn threw ecus thank you for any help i can get i was thinking of buying a third ecu but would like to perform some test to know for sure that the ckp burned the ecu and not something else

holmesnmanny

Do you know how uncommon and rare it is for a 97 prelude ecu to go bad ?

Put everything back the way it was before you started creating problems, replace the ckp sensor harness and see if it's fixed.

motoxxxman

actually holmes, it should be worded; "do you know how uncommon and rare it is for any Honda ecu to go bad as long as it does not have water damage?"
but yeah, prelude ecu's are the most rare to go bad.

how do you know it has a code zero?
97 prelude is obd2. did you connect a code reader to actually scan the codes?
put the 97 prelude ecu back in. drive it. get it scanned with an actual code reader and retrieve the actual obd2 code sequences.

stc876

I'm assuming pretty rare but I don't belive anything I've done thus far has created a. Problem I never got a code for ckp I just noticed it was frayed... I tapped it up and checked the countinuty on it and it had the proper amount. The obd1 distributor runs with the obd2 ecu with out a cel or code. And if it was a fault ckp/tdc sensor wouldn't my obd2 ecu with my obd 2. Dizzy have picked up a code?

stc876

The only way I know it has a code zero is because when I jump my ecu it comes up solid with no flashes I have yet to connect a code reader because when I asked my mechanic he said they didn't have a specific enough code reader to pull codes beyond what I could see with my jumper cable... Where can I take it that can pull more specific codes?... Honda?

holmesnmanny

If he doesn't have an obd2 scanner...i mean seriously he doesn't have one ? ...just go elsewhere. Most auto stores will pull for free. You can also use the paperclip method if you want to pull it yourself. But if it's solid then that means there are none, but there really should be a code in there for an obd2 car to be in limp mode.

stc876

Yes exactly what I was thinking doesn't make sense to have no codes but he said that he has a obd2 scanner he told me I would need a dealer specific code puller to pull a code that hasn't set off the cel I will call around a few places and get the car in for a scan with the. Obd 2 ecu. See if they can pull something... Also my head is missing two manifold bolts casuing a huge leak prior to the o2 could that be causing a head preassure issue making it not rev past 3500k rpm? Also I'm getting no code saying the o2 is getting a bad reading

stc876

I just got back from talking to him I misunderstood what he said he said there is no reason to. Scan it if there is no check engine light on there will be no code I drove the car a lot more then I would of liked to to try and get it to throw a code using obd 2 ecu and obd 2 dizzy not a thing

holmesnmanny

That exhaust leak is going to kill your oxygen sensor in no time. It will also do damage to your cat. Fix the exhaust leak, then replace the oxygen sensor and see if your car is still in limp mode.

However, you should put everything back to obd2. It's not just plug and play when you go down to obd1 you have to change a few things and get a distributor conversion harness or rewire the distributor.

If you go back to obd2 like you should have stayed you can avoid all that. Then after fixing the exhaust leak and oxygen sensor you can try to find the problem.

A solid check engine light after jumping the connector means you have no codes.

stc876

Okay thanks for the help so far but the o2 sensors have less then 1000km on them I put them in after limp mode started(it had. None before)... Also I don't have a cat so the o2 sensors should pick that up.... They are o2 sensors from a honda that are identical to prelude ones but not from a prelude could they not be reading anything but not getting a cel because they are plugged in????

Also I have put the obd2 ecu back in for diagnostics

I have a obd2 - obd1 conversion harness for my distributor running from my obd1 dizzy to obd2 dizzy plug and another wire running to ckp/tdc and its not causing any problem with the obd2 ecu

Tonight I am planning on stopping by honda to get egr gasket and ports. I am going to take of injectors and clean them with fresh gas then clean out the egr valve and port.

I do plan on fixing exhaust leak I just can't get the. Two bolts out of the head

stc876

Okay so I figured out what's wrong with the car and posted incase any one has the same problem and stumbles apon this thread...... It was the timing I finally broke down and checked my crank shaft was off four teeth but both cams were on so it never set off a cel made the exact same situation as limp mode but it wasn't so before spending money on diagnostics make sure you know your timings on