Electrical gremlins in my car ONLY at track days?!
 

Help, my car has a Gremlin and it is driving me mad!

Apologies for the big post, but I'd really appreciate any ideas.

I'm not sure what is going on but only at track days I am getting the following problems:

• Speedo gets a mind of its own. It will read numbers at random and today it even stuck on 0 for a large part of the day, even when doing 130mph+
• Petrol gauge has a mind of its own. I had a quarter of a tank and in one instant it went to empty! I went and filled up and only 45l went in. On the drive home I watched it go from one quarter of a tank to just over half full one notch at a time moving up one notch per second and then stopping and then going back down in the same way. It also kept moving erratically the whole drive home.
• Check Engine Light is coming on sometimes and wont clear. Pulled the code, P0720, 'Output Speed sensor unit' is the fault. I'm not convinced the sensor is at fault and causing the speedo errors, as you'll see later on.
• Steering wheel light and '!' next to it is coming on some times.
• Car won't rev past 6 or 7k approx occasionally. Normally 4 laps or so in the car won't rev past 6 or 7k, tends to be on the main straight and not just after the corner. It doesn't bounce off a limiter, it just won't rev past it. I leave it a few corners and all is back. No engine fault codes present on ECU.

Until today only the speedo has played up before and has caused the engine and other light mentioned above.

I have a Hondata Flashpro fitted to the car and also a yellow box from having a 4.44 rear gearset fitted.

I got the flashpro and yellow box at the same time and the problem has only been since they were fitted.

With just the speedo problem I was thinking it was a yellow box problem. However with the fuel gauge and power cut starting today I am thinking it could be flashpro related.

I tried clearing the code (P0720) at the track via the Torque app but it wouldn't go. At lunch after about a five minute rest it wouldn't clear. The speedo mucked up the whole way home including after stopping the car and switching off for petrol. I also switched off after each run throughout the day and that didn't help.

Here is the interesting bit. I get home, leave the car turned off for 20mins whilst washing the wheels. Turn it back on and I can clear the code and CEL light! Speedo now works fine again. It as always F'ing does this when I get home! :banghead:

Given this only happens at the track and does seem to sort itself out when home I have come up with some crack pot theories:

• The extreme cornering only seen on the track is causing a loose connection or earth, perhaps as a result of the flashpro install or yellow box.
• Heat, the car and perhaps ECU (?) are working at much higher temps causing some sort of issue.
• Speed, the car is never driven above 100 normally, perhaps there is something up with the flashpro or yellow box that doesn't like the higher speeds.
• Power cut could be down to the mapping?
  

Any ideas?!! I'm thinking the car needs to go back in for the Flashpro to be looked at.

I've all this on video so I'll have to work on an edit to post up here.

Thanks a lot if you made it this far :thumbup:

PS I only drive the car a handful of times a month so perhaps not long enough/hard enough on road for it to rear its head but perhaps all these problems are always there, it just takes a days solid days driving to clock enough time up on the car for them to show themselves?

I go with the Gremlin idear :ponder: .

mmm, people getting this code with HOndata Kpro before

https://www.s2ki.com/s2000/topic/821...o-on-a-my2006/


Also looks like there is more than one way the yellow box could be wired up.
https://www.s2ki.com/s2000/topic/815...elerates-slow/
https://www.s2ki.com/s2000/index.php...&f=22&t=119078

It has to be down to all this I reckon :ponder:

lol, thanks for giving it a read :)

Check your battery stays and connections for a starter.

Check all your earths in the engine bay too.

That does sound weird, hope you still had a good day today though, its not much fun being at a trackday with a car that doesn't want to play :(

From reading the other threads, it seemed the errors were more common when the yellowbox was wired up close to the ECU rather than taking the feed wire off the speed sensor on the transmission housing.

If i was guessing, i'd say that if you wired it close to the ECU you were somehow changing the resistance in the circuit by shortening the length of the cable and the ECU picks this up as a fault hence the limp mode situation either that or something in the yellowbox itself sends an incorrect signal when it's cable run to the ECU is decreased.

Cheers, but I checked the battery before today as that sounded like a probable cause. :(

It has been wired up right next to the ECU, perhaps that is why then... I feel this all has to be something simple like that. My car is goingt o Dixon for a service, I'll ask him to give that a go and cross those fingers. I don't get why only track days bring out the problem though :suspect:

It was the best track day ever, once I knew the CEL wasn't anything serious and the rev issue didn't happen too much. All I can say is Stoptech rule :rockon:

I've just read your other topic, sounds like a great day! My last one was the same, lots of people talking and after instruction I got a 3:01 best lap :D

Makes me feel good knowing I'm not all that slow!

That sounds like a quality time given the extra work my car has had done :thumbup:
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The speed sensor wiring explains the speedo, the EPS fault (it goes into the EPS too), the CEL, and the 7k limit on the revs because it's gone into limp home mode. And usually, switching on and off again will clear it - until it happens the next time.

I had all the same thanks to a well known specialist doing a bit of a half-arsed job on the wiring, and left a connector partly exposed so it could short against the chassis. A bit of electrical tape, and I've never had a problem since.

And the ! next to the EPS will be the brake fluid low indicator, which you might expect on a trackday with heavy braking and pads that are getting low.

As for the fuel gauge, well it's an S2000. None of them work properly. :D

Thanks, it really does sound like something asnt been done correctly with the wiring doesn't it.

The '!' was only coming on and staying on with the steering wheel light. Brake pads all new that day and brake fluid just below max and still was at the end of the day and my brake pads wore 1mm max (new bbk with endurance race pads)

As for fuel gauge, they are pants but counting up and then down over about ten seconds whilst sat at lights it was like watching a fruit machine! It was going crazy.

I'll look to get the wiring checked over and hopefully tha twill sort it.

Thanks again

The instruction easily wiped 15 seconds off my laps, and I was already a lot quicker than last time in April when I had my squeaky brakes and shabby 6yr old bridgestones. :)

What tyres have you got on the enkeis now?

I've got 215 and 245 ad08s on the car. May go a bit wider next time but with an 8inch 50mm wheel up front it may rub and don't want any hassle like that to deal with.

Got the rear brake sorted then, it was sounding ghetto that day :LOL:

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Does the stock ECU have a memory/data function?

I still think this a bad earth reference...

:shrug: Sorry, haven't a clue, it is the standard ECU reflashed with the Flashpro.

No.

Sounds like the yellow box speedo fudge is not done properly, all the issues you are reporting are due to the speed sensor.

•Speedo gets a mind of its own. It will read numbers at random and today it even stuck on 0 for a large part of the day, even when doing 130mph+
•Petrol gauge has a mind of its own.
•Check Engine Light is coming on sometimes and wont clear. Pulled the code, P0720, 'Output Speed sensor unit' is the fault.
•Steering wheel light and '!' next to it is coming on some times.
Car won't rev past 6 or 7k approx occasionally.

- Speedo sensor signal messing up
- What's new - petrol guage doesnt help
- CEL confirms speedo signal
- EPS relies on speedo signal
- ECU thinks the car is stationary, it wont allow VTEC and limits revs when the car isnt moving.

It sounds like the yellowbox is the cause of your problems, probably a lose connection or something.

Has your fuel pump ever been out? The senders can get knocked off their mounts pretty easily putting them back in, this results in the readings being all over the place

Yep, going to try a new yellow box and get the wiring looked at. Hopefully its just that.

The fuel gauge was an odd one though, I've never seen it be so erratic. The fuel pumps never been out.

Thanks for all the suggestions, I'll report back after I've had the yellow box looked at :thumbup: