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Limp mode?

9.5K views 12 replies 4 participants last post by  SSB4  
#1 ·
Hey guys, any of you that did an engine swap to and X with X ECU and cluster have any problems going faster than 30-40mph? The car was running fine at first hitting 60-70mph but all of the sudden after a few hours of running it won't go faster than 30-40? Any ideas. Getting code P003 - O2 Heater Intermittent/open. I want to say that is only part of the problem but I'm not sure. Thought might be in limp mode but I don't get code 1000 or whatever. But it does act like it's only giving us half power. Any idea?
 
#2 ·
I would check the wiring harness for spots that may have rubbed if you still have your factory ecu and cluster they will work you will just miss out on a little bit of performance but maybe that will tell you if your having a issue with your new ecu hope this helps
 
#3 ·
I didnt have any issues. Certain codes cause limp mode. What is that code? Its not oxygen sensor is it? Flash for a 2015?
 
#4 ·
I will definitely check the harness and see if that caused it. Hopefully it's going to be a simple fix.

Based on the manual it says: O2 heater intermittent/open. Not sure what that means. Not really sure what they flashed it for. Both ECU and Cluster are new X model so I figured there should be any problem.
 
#5 ·
Assuming you have an O2 sensor on it and wired properly to an appropriate ECU, that code would suggest a bad connection somewhere, like a plug, or a defective O2 sensor. If you added an O2 sensor to a vehicle that did not already have it, exactly where you located the sensor could be critical. They need to reach a certain temperature to work, as I understand it, and if it's too far down the exhaust system it might not get hot enough to work under some conditions. That would piss the ECU off, and it might go to limp mode.
 
#6 ·
Sounds like you have wrong ECU. I read to quickly first time. You dont have a wiring harness for an O2 sensor. I would check part numbers on ECU. Sounds like you have 2015 ECU
 
#7 ·
"O2 heater intermittent/open"

I suppose the 02 sensor has an electric heater built into it to get it up to operating temp faster and keep it there when idling, etc.

If that (resistance) heater failed, or if there was a electrical plug problem (likely) or a wiring problem, you'd see the same code even if the sensor itself was OK. It's a 2 part device: The O2 sensor itself, and the auxilliary heat element. I'd carefully check the wiring and plugs, then try it again. If there's no change, you might try the battery disconnect/reconnect ritual. I'd guess it's sensor plugs or the sensor itself.

It might stay in limp mode by reason of having set the code even if the O2 sensor actually works some of the time.
 
#8 ·
"Sounds like you have wrong ECU. I read to quickly first time. You dont have a wiring harness for an O2 sensor..."

You'll have to get that straightened out, either by adding an O2 sensor in the correct location or getting the right ECU for the suite of sensors that your engine has.
 
#9 ·
Patrick, TXGOAT

Thanks a lot. That does make sense! We were ran out of time with our repairs for the Baja 500 that we just had to order an X ECU without even thinking what year WC. That mistake cost us big time too. Wish we had the time to send it to Evo but I guess you learn something new every time you DNF, just getting tire of it lol.

I'm assuming Evo reflash will fix that issue, right? Or do I need to send my old ECU?
 
#10 ·
I'm not sure on EVO flash for that. Best give them a call and see what they say
 
#11 ·
I'd guess the late ECU would have to have a working O2 sensor input to work at all except maybe in start/warmup mode. I don't know which setup is best for performance/driveability. I'm guessing the late ECU with O2 sensor would be wanting a catalytic converter, too. The late ECU/O2 outfit may be an emissions compliance setup more so than an improved performance setup, and it might be harder to do reflashes or other modifications with it. I'm beginning to think I'm glad my WCX is an old, outdated '14 model....
 
#12 ·
you can run your old ecu and gauge and that should tell you if its your ecu or not the only thing is when you hit the go petal you may hit the rev limiter do to stock redline is 7200 on your factory ecu and that is where most stock x clutches tend to run but you will not be in limp mode with your old electronics it would be a good way to tell before you drop some coin on a Evo reflash and I ran my x motor with stock ecu and gauge for months with no issues only reason I did a reflash is I wanted all the performance I could get