Blown ecu via lambda short (anyone know the ground pedal wire trick?)

[Gregor170590]

hi everyone this is my first post/thread on the forum I usually just search and read until I find what I need but wasn't so lucky this time.

i'll start off with what happened and then go from there. I have a leon 1.8 20vt and noticed the wires for the rear lambda had been hanging low and were broken so I got a new lambda sensor but as I moved the car to where it could be lifted to gain access to the underside, it suddenly jumped to 5k revs and the epc light came on so I immediately switched the car off.
anyfurther tests resulted in the car revving up to 5000 revs unless the brake pedal is pressed then it idles as it should haha

even after changing the lambda and checking all the wiring (with no issues) it was still the same.
I had even tried another throttle body and accelerator pedal to be sure it wasn't them but after finding a few posts on here I quickly realised the lambda wires must have shorted and blown my ecu.

Now I know that the common practice for this situation is either buy a new ecu and get it coded or have the current ecu repaired .........However i have read on two separate threads a method of running a direct ground from one of the pedal wires. it does say its not great but it does get the car going again.

it wont let me post url for these threads as im still noob

There is a way to get the pedal working by running a direct ground from one of the pins on the pedal switch, Its not ideal and doesn't fix the ECU,
I'm sure the Lambda wont be working correctly either as the Grounds are fried.

All sorted, Well in a way!!! the o2 sensors had shorted out the ecu by the previous owner, so instead of them replacing the ecu they wired the pedal to run off one of the two sensors, the mechanic found a split in the connector where they did the bodge wiring, he replaced it but told me the pedal is working again BUT the ECU is the problem """"part of the ecu controls the tpc and when the o2 sensors shorts for any reason, it burns one of the resisters that talk to the tb, this is why the car had no throttle response and was idling at 1200, as the ecu is partly minced when you press the brake pedal it revs high and this is because the brake pedal is controlled by a much higher voltage and the ecu confuses it with the sensors from the tps resulting in 5000 rpm"""".
The wiring has been bodged to run off one sensor atm, he told me to grab another ecu soon, i'm paying him next week and he's told me he will write up a full report on all faults and codes, so if anyone else is having this problem, this may help Thanks Lee69

At this point I've had my head buried in wiring diagrams for the last couple of days trying to work out what wire to ground. i think it may be the G185 that i want to ground but i aint brave enough to try it.

can anyone who know about this or has done it help please.

cheers Gregor

 

[Gregor170590]

cracked it

here is the answer for anyone else that manages to short out their ecu due to a lambda short(lambda wires got pulled/broken and caused epc light and very high revs).

run a direct ground wire to pin 5 on your pedal connector

that's all

it put my epc light off and returned my idle back to normal

the ecu still needs replaced but this should work until such time


cheers Gregor

 

[mty12345]

Good work mate, glad you got it sorted and that's useful info for anyone else that has a similar issue.

 

[DaveLeoncuprawolfe]

I'm having similar issues epc,changed tb,crank case pipes ,my original accelerator pedal now does nothing ,1st used idle was 2300k second used is climbing right up ,when brake pedal is pushed idle drops to normal like ur car .....
Can u tell me what wire is number 5 furthest away (firewall ) when pedal fitted ?,can u remember colour ,also can u remember where u ground it ?,having a nightmare tbh ! So any help much appreciated