No rpm on speedo and car idles high??
 

Hi guys,

Searched through all the forums and can't find where to go next....

Basically car hasn't been used much for a year then I started it got mot done, serviced it and everything seemed fine.

Couple of days later the engine rpm on the speedo stopped working and the idle speed went high, about 1500-2000 I'd say, and seems to climb as the car gets warm..

Sweeping gauges work fine at key on.... and everything else on the dash works.

I figured a speed sensor issue but can't seem to find in the manual exactly which sensor is responsible for the tacho.

Have no light on the dash for CEL...

Any ideas lads and lassies?

Thanks! :wonder:

When you say Sweeping gauges, is this a JDM dash ?

Ive not got the answer you need but trying to get more inform that someone may get a better idea.

Hi Chris,

Yes a 03 JDM sti, with a simtek ecu fitted...

In the ye olde days vehicle speed was transmitted by a cable from the gearbox to the dash dials, then it changed to an electrical sensor usually mounted in place of the cable. Abs came along and now speed is calculated from the wheel sensors, but there were some cars that had abs and a seperate sensor in the t/m as well.

Might be worth checking if there is one on your car?

Cheers, I bet ye old days it was easy fixs stupid issues like this, lol!

Speed sensor is on the trans, but the speedo works fine also.

It's the engine rpm I've an issue with... could be either of the two cam sensors or the crank or all three combined, or could be the signal from the ecu to the dash.....im going to check the sensors with an oscilloscope later see if I can find anything.

Keep the suggestions coming tho thanks!

Well while it was parked up the battery was out and on a smart charger to keep it healthy...

When reattached it started straight away, then drove for about 5days starting and stopping fine, just out of the blue the rpm stopped showing

Ok a bit further on this issue....

Checked signal from sensors, all fine.
Checked signal from ecu to dash, nothing.

Put my old original ecu in to try that and my rev gauge works fine and car idles correctly..


So looks like I have a controller issue.....what do I do with an old simtek?? Anybody know what could be wrong or more importantly anyone able to fix a broken one?

https://cimg1.ibsrv.net/gimg/www.sco...93c94331ad.jpg

This I guess is the issue....

So that's burned out, Not sure if those would be repairable, Back in the day I done specialist repairs on computer motherboards where I could remove and replace smt chips including pads and tracks however it was all specialist equipment.

I bet those ECU's ain't cheep hopefully It can be repaired and what ever caused the issue resolved.

From my investigating, I think the chip is a voltage controll gate... so hopefully not configurable and can be swapped out....anybody know anyone capable of swapping this chip?

Or is there anyone with experience on fixing alcatek/simtek ecus?