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

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Eniallan
Posts: 9
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: 9
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: 5275
Joined: 21 Sep 2002, 19:07
x 318

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: 9
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.
Eniallan
Posts: 9
Joined: 24 Jun 2020, 22:55

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

Post by Eniallan »

Back again with this issue, was kept busy with tiding the engine bay and fixing exhaust and bodywork.

What I have found is when the fuel pump main feed is disconnected from the fusebox, voltage on the pedal connector (pin 3), with ignition on, fluctuates up and down from 9.7v to 9.98v.
Connected it goes no higher generally than 9.6.

What I also notice is when no ignition on, turn on hazards, get a minor bit of voltage on the affected pedal connection (pin 3, ECU pin E1), up to 0.03v each time it flashes. I'd have thought this is not important since its minimal, but I thought the ECU was effectively isolated (bar earths) till ignition is on to liven the relays to it.

There is no other issues on the engine sensors, all read correct voltages and otherwise function correctly. Only faults that exist are on the ECU for the pedal and throttle. Nothing else plays up.
Fault_diagram.jpg
Really how someone can help, I'm a bit lost now with where to go with it.
wheeler
Posts: 5275
Joined: 21 Sep 2002, 19:07
x 318

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

Post by wheeler »

wheeler wrote:
12 Aug 2020, 17:20
have you tried directly earthing the ECU casing straight to the battery negative?
Did you try this?

When you say your removing the fuel pump feed are you just removing the single wire or unplugging the full 28 way Grey connector? If you are removing the full connector i would expect to see some of the voltages going haywire.
As for turning the hazards on, this can wake ECU's up. On some cars (particularly keyless models) when you cant get comms with diagnostics turning the hazards on can wake up the system & allow comms.
Eniallan
Posts: 9
Joined: 24 Jun 2020, 22:55

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

Post by Eniallan »

wheeler wrote:
11 Nov 2020, 15:51
wheeler wrote:
12 Aug 2020, 17:20
have you tried directly earthing the ECU casing straight to the battery negative?
Did you try this?

When you say your removing the fuel pump feed are you just removing the single wire or unplugging the full 28 way Grey connector? If you are removing the full connector i would expect to see some of the voltages going haywire.
As for turning the hazards on, this can wake ECU's up. On some cars (particularly keyless models) when you cant get comms with diagnostics turning the hazards on can wake up the system & allow comms.
Yeah, it did reduce voltage a little. Roughly .5-.8v.

Just the single terminal (pin 5) for the fuel pump motor removed. What it seems to be happening, anything that connects from that connector seems to reduce the pedal voltage or on the throttle motor earth when connected/operated . The reverse light switch for example, if I work the switch for the lights, voltage will reduce a little. Assuming, completing any circuit like the pump, reverse etc is 'earthing' it, probably windscreen wipers too would affect it if I turned them on.


Tested the pedal, with everything where it should be and nothing disconnected, getting .87v reading on the pedal pin 1, .48v on pin 2. Pin 3 is still 9v+, pins 4 & 5 at 5.48v.

Added in a new earth from the BSI, theres an unused earth out on one of the 10 pin connectors, it again reduced voltage by a small amount.

I just can't see where the issue is coming from, wether its an obscure earth fault, or something drawing too much current, which was a problem of the throttle from damaged wiring.
Any tips or suggestions to trace down the fault.
Eniallan
Posts: 9
Joined: 24 Jun 2020, 22:55

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

Post by Eniallan »

No luck still, noticed the two locking buttons on the centre dash were lit up but dim with ignition on and remained dim after the ignition off, till I disconnect the battery, found that the central locking switch is getting strange voltage issues.
Two videos below shows basically whats happening.