Help with Electrical fault

[VAG-Abound]

There are some interesting ideas in here for tracking down what is affecting the 5V lines: Skoda Octavia 2,0 TDI CR 2011 CFHC P0641 - Fixed - Pico Technology

Ones that caught my eye:
1) Pull the ECU and find (via multimeter) which pins seem to share the same internal track as a component known to be fed with 5V (so find that out on the Hall sender assuming it gets 5V)
2) Clamp ammeter on the wires to look for current spike indicating internal shorts in components. But I think you have the opposite - open circuit would lead to loss of current draw I guess.

[Dieseljuice]

Thanks for that...busy building a patio so car will have to wait....having to use the wife's car!
Still googling....I think I read somewhere the sensors take to 5V and send back a voltage based on sensor value.....if true and open circuit fault then should I not expect the faulty sensor to be reported alongside 5V open circuit generic fault?

Or is the ECU so clever that it measures current drawn from 5V pin supplied by ecu and if no current drawn then it just reports open circuit ....though again I'd expect it to report all sensors that take that 5V as none are giving a signal back...or am I assuming too much?

Thinking of taking it to another auto elect or even dealer to get a second opinion....or bite the bullet and change EGR and hope its that else its a ECU. But found on another forum an audi I think it was with a similar fault...but I think it also flagged an egr fault.....then another forum a 2010 jetta with 5V open circuit...guy eventually took it to a garage and they managed to get it to report another fault...egr...and new EGR fixed it.

Normally I'd buy VW egr but I'm thinking of buying a new car. I would like to sell the car without faults. Any comments on after market egr's.....a decent make like Valeo or ? Dealer egr is almost £500.

Is there a way I can check 5V rail and egr with Vagcom?

Thanks again for the help and advice.

[Dieseljuice]

So had a play with VAGcom. Cannot see how to view 5v rail but maybe a breakthrough...or clue?

OK car had normal fault on turning ignition on but not started car.....Voltage open circuit fault. So cleared it and started car.

Was looking at egr values and did not notice any 99% or 100% values but then as car heated up then suddenly engine revs higher and flashing coil...scan showed open circuit and G28 speed sensor and the values below was the screen shot when the fault happened.



Screenshot 2022-07-16 160338.jpg





So cleared the faults and flashing coil, engine speed dropped

Viewed below and noticed


Address 01: Engine (03L 906 018 )

16:17:17
IDE00405 Crankshaft speed (RPM) 781.0 /min
IDE00473 EGR Vacuum Regulator Solen.val.: activation 65.88 %
IDE00581 EGR specified value 34.5 %
IDE01259 EGR Solen.val.: actual value 65.44 %
IDE01361 exh.gas recirc. (EGR) cooler pump: specified value 95.00 %
IDE01363-ENG57549 exh.gas recirc.: shut-off conditions-Bits 0-7 255
IDE01363-ENG57549 exh.gas recirc.: shut-off conditions-Bits 0-7 7
IDE01363-ENG57549 exh.gas recirc.: shut-off conditions-Bits 0-7 0
IDE01363-ENG57549 exh.gas recirc.: shut-off conditions-Bits 0-7 0
IDE01373 EGR valve: offset closed 3.71 %
IDE01374 EGR valve: offset open -3.71 %

So now no 99% or 100% egr values......so is the egr going to 99%/100% causing the problem.....is a faulty egr?

Hoping it is and not the ecu.

[Crasher]

Aftermarket EGR valves can be terrible, the last one we fitted to replace one under warranty was an upgrade from the supplier, it failed before we could get it off the lift. No if an EGR valve takes say half an hour to fit then it is not a huge inconvenience but on a CAYC engine it is a days work. From what you have posted I see no indication that the EGR unit is faulty.

[Dieseljuice]

Thanks for that Crasher. Not sure what to do now...... I think its going to the VW dealer for checking......then VW dealer ECU fitted. Killer £££££££
Thing is I do not want dealer emissions software upgrade.....maybe part ex and take the hit!

[Crasher]

I hate blaming the ECU, it stems from my experiences during the mid eighties where people would pull the full system from a type 3 TE and swap it for the TL system blaming the “black box” only for me to find it was just the cylinder head temp sender at fault.

[Dieseljuice]

New clue? On switching on ignition (not started car yet) I hear clicking and tach twitches to about 500rpm and dash lights flick off then on....all in a moment....then normal eng fauly message and eng light on and flashing coil. Engine sometimes hard to start, I only try a second or so. Then turn off, pull key, key in....sometimes no faults and car starts ok without fault. Hardly have to drive far and flashing coil and sometimes eng light on too. This is now a daily event.

Does this prove ecu?

still on with patio......will decide next week. might just sell it and declare fault.....great car in as new condition bar this electrical fault.

[Dieseljuice]

Update. Pulled all sensor connectors under bonnet i could find and cleaned with contact cleaner. Fault has gone.

[Dieseljuice]

Just an update. Fault came back in March, then gone again, then back.

Crasher was correct - its the ecu.

Trying to get it repaired, if still no good then a new one.

[Crasher]

If it can't be repaired (highly likely) don't hang about as that ECU may go obsolete very soon, what is the VIN?