Car is a 99 civic running a chipped OBDI p72 with a conversion harness, problem is when my car's CEL comes on, i'll turn the car off and turn it back on and the CEL will be gone, before i even get a chance to jump the plug and pull the code. I don't think its the ECU cuz i've ran three different ECU's and same thing.

 

you know i am expeirencing quite the same problem. i posted an earlier post in the all motor (didnt know, notice NOOB), anyways when i am getting it on and vtec pops, 3rd to 4th is fine and when i let off the check engine light comes on. when i shut the car off and start it back up its gone. car runs fine though, idles great, running a P28 OBD-1 with jumper with hondata s100. Im thinking the back pressure in the stock is throughing the o2. not for sure. but anyone can kill 2 birds with one stone for these problems? thanks

 

Go thru the motions of reading the error code anyway. It should be stored in the ECU, even tho the CEL has turned off.

 

or when the cel comes on jump the connector without shutting the car off

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">or when the cel comes on jump the connector without shutting the car off</TD></TR></TABLE>

And will the CEL blink?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">or when the cel comes on jump the connector without shutting the car off</TD></TR></TABLE>

Yes it will blink normally, this is what I had to do to find my cel code.

It will work.

 

Ok this is so simple. Run the car. Get th CEL light on. DO NOT TURN OFF THE CAR!!! DO NOT. Now check the code. Willing to bet its Oxygen sensor / fuel related. The reason why it goes off when you turn the car off is because the O2 is reading a good level at idle and does not notice a problem. The reason it turns on at high rpm is because the mixture is wrong then since you are putting in more air and more fuel. Now if you rewired your Oxygen sensor, check for shorts. Dont just replace the O2. Check first if O2 is operating. On older cars that are single wire O2, be sure that the ground wire that sleeves the actual O2 wire are not touching each other as this will short the circuit.

 

when my uberdata did this it ws the o2 snesor even though it was shut off.

Never made the car run lean or anthing so i didnt care

 

as far as i know and believe me i dont know if the o2 sensor has been rewired. when my mechanic did my exhaust he never said anything and we tuned it with hondata s100 and it seemed to be fine. even though it is tuned greatly this can still happen at hi rpms? now if i do a high flow cat will the CEL stay. will i have to retune or get a new o2 sensor? thanks for your reply.

 

Doesnt matter how its tunned. Check for the code. Check wiring to the O2 sensor.