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Author Topic: ED35 CDL sudden poor starting, misfires, general poor running, no boost  (Read 414 times)

Offline john_o

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no recent changes
car running great
54k miles

just went out to the car after work on Thurs, it started but misfired, i turned it off then it was ok and i drove home...
then went to use it again an hr later and it barely started, and i get EPC/EML lights on, and its barely driveable , just bogs down

VCDS scan shows me at least 4 things that now appear to have no power (which implies an upstream relay, fuse or cable issue , hopefuly not the ECU!)

Quote
4 Faults Found:
008852 - Fuel Pressure Regulator Valve (N276)
               P2294 - 004 - Open Circuit
             Freeze Frame:
                    Fault Status: 01100100
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 88207 km
                    Time Indication: 0
                    Date: 2050.14.20
                    Time: 21:43:24

             Freeze Frame:
                    RPM: 756 /min
                    Load: 20.0 %
                    Speed: 0.0 km/h
                    Temperature: 66.0°C
                    Temperature: 41.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.224 V

001112 - Evap System Purge Control Valve (N80)
               P0458 - 002 - Short to Ground
             Freeze Frame:
                    Fault Status: 01100010
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 88207 km
                    Time Indication: 0
                    Date: 2050.14.20
                    Time: 21:43:25

             Freeze Frame:
                    RPM: 765 /min
                    Load: 20.0 %
                    Speed: 0.0 km/h
                    Temperature: 66.0°C
                    Temperature: 41.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.097 V

000052 - Turbocharger Bypass Valve Control Circuit
               P0034 - 002 - Low
             Freeze Frame:
                    Fault Status: 01100010
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 88207 km
                    Time Indication: 0
                    Date: 2050.14.20
                    Time: 21:43:25

             Freeze Frame:
                    RPM: 765 /min
                    Load: 20.0 %
                    Speed: 0.0 km/h
                    Temperature: 66.0°C
                    Temperature: 41.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.097 V

000581 - Solenoid Valve  for Boost Pressure Control (N75)
               P0245 - 002 - Short to Ground
             Freeze Frame:
                    Fault Status: 01100010
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 88207 km
                    Time Indication: 0
                    Date: 2050.14.20
                    Time: 21:43:25

             Freeze Frame:
                    RPM: 765 /min
                    Load: 20.0 %
                    Speed: 0.0 km/h
                    Temperature: 66.0°C
                    Temperature: 41.0°C
                    Absolute Pres.: 1010.0 mbar
                    Voltage: 14.097 V

Battery voltage is good (see above)
i have checked some fuses but not found any issues (so far), am i missing an obvious fuse thats just blown here ?
i have replaced the '100' relay to prove its not that (same behaviour),

Anyone on here had similar issues / fixed them ?  cant see 3 seperate components going at the same time so in my head it should tie to a single central issue.
which at this point looks like a fuse/relay ive missed , ecu or broken wire



Red ED35 5dr DSG
DEFI boost guage / RTech Stg1 Engine/DSG / PPMk7 front brakes
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Offline Pudding

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Have a look at the main harness under the vacuum pump.  It rubs on the pump housing and a wire might have worn through and shorting on the metal housing.  Two of your faults are short to ground, so that's where I'd be looking in the first instance.


2007 ED30 | 2009 TDI 140

Offline john_o

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cheers for the reply @Pudding  , sounds plausable, Ive now handed it to a trusted local garage (who generally look after it) , lets see how it goes.
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Offline john_o

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Wiring all checks out
Fuse box replaced
Issue now permanent not intermittent
alas its looking very ecu related  :sad1:
Next up is an ecu swap with immob removed just to prove it.
Then its decision time on swap for 2nd hand and/ or get original repaired
I have an rtech remap , can get it redone but a pain tbh
No mention  of water damage
Car bang on 10yrs old this month
Let's see....
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Offline Pudding

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Bummer.  Not a common occurrence for an ECU to pop but as so many sensors share the same voltage reference line, the fault codes are pointing in that direction.

What I would be investigating before getting a new ECU is what caused the reference line to blow in the first place?  Short circuit? Bad mapping/tampering? etc etc.

It is possible to copy your old ECU to a used one, but obviously both will need sending off to a specialist.



2007 ED30 | 2009 TDI 140

Offline john_o

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totally agree
nothing has changed on my car for years! i just run it and service it myself.
only thing Ive done (around this time) was charge the battery (which Ive done many times before) and its a ctek charger, so maybe it was that ....

Red ED35 5dr DSG
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Offline john_o

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the car is back and fixed.

symptomes were reduced voltage (3V) against the circuits indicated as faulty on the fusebox
garage tried an ecu swap and it made no difference, so they went back through the continuity loom check and they then found a short under the fusebox as it bends and passes through metal
(anyone got a picture of the loom routing under the fusebox by any chance?)
at that point they also worked out the relay had been taken out by the problem.

So in all
new relay
a few new fusebars (precaution)
new fusebox engine bay  (changed but not convinced it was actually needed)
repair loom short
4 hrs labour

final bill was just short of £700, of which 50% is parts and 50% labour.     

Garage have been brill in progressing this work, I left it with them indicating they had as much time as needed to resolve and no rush
that way they could work on it as and when around other jobs (they did way more than the 4hrs they charged for)
in hindsight Im not convinced on the fusebox replacement, but they also sourced a replacement unlocked ecu (temp) which i couldnt have done, nor was I charged for it.

moral of the story , its usually something simple.
Anyway the cars back and Ive missed it

thanks @Pudding as ever for the interaction



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Offline Pudding

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And thanks to you also for following up  :happy2:  I wish everyone did, and then we'd have a more complete knowledgebase!  :smiley:

The knowledge we've gained here is: with so many electrical faults flagged by the ECU, check for short circuits and/or wiring defects, missing/blown relays etc.

Problems like that are a complete nightmare but kudos to the garage for being so thorough.  I'm glad it wasn't the ECU in the end as they almost never fail, so that's saved you some grief and aggro sourcing one and coding it etc.

I forgot to mention that whilst compression testing my engine, I couldn't find a way to disable the fuel pump, so I pulled relay 167 in the engine bay fuse box.  I then got exactly the same fault code list as yours, so I was meant to reply to this to get your garage to check the power feed to that relay......but you got there in the end anyway :happy2:

And for the record, pulling relay 100 takes the ECU out, so no fuel or spark during cranking for compression testing  :happy2:


2007 ED30 | 2009 TDI 140

Offline john_o

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too many learnings for one day  :laugh:
lots of information gold
Red ED35 5dr DSG
DEFI boost guage / RTech Stg1 Engine/DSG / PPMk7 front brakes
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