207 Electrical issues from ecu/throttle, high voltages on accel pedal

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Eniallan
Posts: 3
Joined: 24 Jun 2020, 22:55

207 Electrical issues from ecu/throttle, high voltages on accel pedal

Post by Eniallan »

Hopefully someone can lend some help to diagnose this fairly large issue I'm having.

I've swapped a 1.6 Nfu into a 1.4, rewired the ecu with the Bosch ME 7.4.5 and 3 wires of one fusebox plug, had it running with a surge on startup but would settle to 1000rpm (perhaps the start of the trouble?), but then one day just went wrong. It idled rough and couldn't rev above 1400. Had the ecu tested but came back okay.

Accelerator pedal was working, even after everything else was failing, now it has gone, initially track 2 yesterday, now track 1 also showing fault.
Im reading 9v on pin 1, 2 & 3 but pin 3 goes from 9.60 to 9.77 erratically. Pin 4 is 0v pin 5 5v.

The throttle body reads correctly on the potentiometer pins 3 to 6, however 3.28v on the throttle motor + and -.
The ecu is earthed, as is the fusebox, wiring replaced even. New and much better earth strap.
I've now also got a p0341 when I ran the engine to get data reading through diagbox. Maybe it's just as a result of the throttle issue, though its the first time I've seen it when the engine has run.

The ecu can see the throttle, when I open the throttle by hand, the voltage and angle values in the measurements show up correctly.

I'm not sure where I should be looking now, but I assume that the pedal and throttle should be 5v?
Can all this be from just one + feed going to the wrong place or in a bad state?

Any ideas on what to look for and check be great. I'll add or provide more info as needed.
Im familiar enough with everything and diagbox so can test anything needed.k


Removed a wire from the ecu today from fusebox, feeds battery voltage, no voltage on pedal, MAP, throttle etc. Connected its normal and high voltages again. Not sure if this means there is a short or ecu issue.

Another edit, I pulled two connectors, a 48 and 28 pin, from the ecu, pretty much all the engine components disconnected from any power, before I just pulled from sensors. Got 5.38v on the pedal again pins 1 & 2, pin 3 still fluctuates with 9.18v up to 9.28v. 5.38 still seems high, maybe its acceptable though.
Not sure if this somewhat normal behaviour, but seems to be isolating the issue further.

Eniallan
Posts: 3
Joined: 24 Jun 2020, 22:55

Re: 207 Electrical issues from ecu/throttle, high voltages on accel pedal

Post by Eniallan »

Just wanted to seek more help, as I haven't resolved it yet.

Ecu has a high resistance between the motor earth and ecu earths to chassis. Both ecu's read the same though. Effectively, it can't be earthing properly, since on my older ecu there's no resistance. I'll have to get the ohm measurement but recall it being fairly high.
It's the same on two ecu's I have though.

Would like to know if all 207 nfu based cars used only the me 7.4.5 or if they used me 7.4.4 or even 7.4.9 like the 206.

wheeler
Posts: 4307
Joined: 21 Sep 2002, 19:07
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Re: 207 Electrical issues from ecu/throttle, high voltages on accel pedal

Post by wheeler »

have you tried directly earthing the ECU casing straight to the battery negative?
What was the issue with the original engine?

Eniallan
Posts: 3
Joined: 24 Jun 2020, 22:55

Re: 207 Electrical issues from ecu/throttle, high voltages on accel pedal

Post by Eniallan »

wheeler wrote:
12 Aug 2020, 17:20
have you tried directly earthing the ECU casing straight to the battery negative?
What was the issue with the original engine?
No, I have considered it and seen mention people do it with other cars ecu's. I'll try it though on your suggestion.

Original engine was a tu3a, crankshaft oil seal leak, I think the block needed a skim or replacing, since no head gasket replacement ever worked or head was worse than the engineer could skim but never mentioned it. It just always lost coolant and oil, may have even been piston rings or unseated wet liner. I'll find out sometime when I strip it down.
Instead of using another tu3a, picked up the jp4, rebuild and fit, basically a new engine now. When it ran, it was great. Bodywork is modified and such, so didn't want to lose the car/chassis for a already fitted jp4 version.

Any help will be great. Starting to get stressful. Help elsewhere had unfortunately been not so great.