P0688 code, EPC light, no throttle response

[Cvetko]

Hey,

here we go, new problems with winter coming
Those problems (P0688, EPC light, no throttle) are happening, when is really cold outside like -5Celsius.
But other days when is not that cold, car is working like a charm, no problems. This happens time to time.
The car starts normal no issues, but you can hear going minimum up an down a bit(itself) and no throttle response.

Checked relay 428 and 219, both fine, fuse #29 is ok too
I think the coils are all fine.
Any ideas what to check, or where to focus?

thanks
cheers

 

[badger5]

17072/P0688/001672

Contents
[hide]

• 1 17072/P0688/001672 - ECM Power Relay Load Circuit: (J271): Open Circuit
  • 1.1 Possible Symptoms
  • 1.2 Possible Causes
  • 1.3 Possible Solutions

17072/P0688/001672 - ECM Power Relay Load Circuit: (J271): Open Circuit
Possible Symptoms

• Engine Coolant Fan running at full Speed while Ignition is OFF and Engine is COLD (could lead to discharged Battery)

Possible Causes

• Fuse(s) faulty
• Power Supply Relay for Engine Control Module (J271) faulty
  • Terminal 87 faulty/hanging
• Wiring between Engine Control Module (J220) and Power Supply Relay for Engine Control Module (J271) faulty

Possible Solutions

• Check/Replace Power Supply Relay for Engine Control Module (J271)
• Check Wiring between Engine Control Module (J220) and Power Supply Relay for Engine Control Module (J271)
• Check/Replace Engine Control Module (J220)

Category:

• Fault Codes

 

[vag-tech]

Can you check measuring blocks via VCDS?

 

[Retroman]

 

[vag-tech]

If main relay is defective you'd get a non-start on account of no power at ECM. If I've correctly interpreted you original post, this isn't the case?

 

[badger5]

no power to throttle body sounds like to me.. Fed off main control relay, but no doubt some dodgy join/wire on the way.

Had this on a CH car before Xmas.. Corroded terminals on the small ecu plug.

 

[Cvetko]

Car/engine starts with no problem, just strange idle at 1100rpm and no response. (Just in cold weather, no issue when is a bit warmer outside).
Tried without relay and wont even start engine.
Than I just wired +/- where the relay supposed to be, and is working the same as with relay, must be something else.

Strange...

thanks cheers

 

[Stuart B]

things shrink in the cold, so may wiring moved a tiny bit?

not something crazy like ice in the coolant blocking something to a sensor?

my original stage 1 map refused boost after first start in cold weather after running for a minute or two a restart sorted it out - have you tried "rebooting"

 

[<tuffty/>]

my original stage 1 map refused boost after first start in cold weather after running for a minute or two a restart sorted it out

That would be a 17705 fault code... It's a software fault that is coded out by tuners that know what they are doing.. Can also be symptomatic of a MAF issue but generally the software issue

<tuffty/>

 

[badger5]

Car/engine starts with no problem, just strange idle at 1100rpm and no response. (Just in cold weather, no issue when is a bit warmer outside).
Tried without relay and wont even start engine.
Than I just wired +/- where the relay supposed to be, and is working the same as with relay, must be something else.

Strange...

thanks cheers

I dont understand fully what you describe probably.. When you say no response, no throttle I read that as literally no throttle function at all. OR do you mean just little boost and it drives ok..

Fault codes 17705 being expected if you have the cold temp limp mode issue

Which is it?

 

[Cvetko]

Amm, yes, no throttle, cant drive the car. Is just idling, as I push throttle nothing happens, rpm stays the same at 1100(very high, should be 600-700).
I discovered that if I let the car idling for 10-15mins to warm up, then next startup is normal and will drive, no problems.
I saw when is cold that I cannot hear throttle plate movement (like "click" sound), engine is DBW, and when is warmed I can hear it and is moving "plate".


thanks
cheers

 

[badger5]

check your wiring at this point. at throttle body and at ecu.. I suspect you may have some corroded pins in the smaller of the two ecu plugs.. Green furry corrosion.

 

[Cvetko]

Huh, finally solved. Dry joints on PCB where connectors goes.
I heated (used hair dryer) ecu plugs small and large one, to see if that was the case, but still have problems, so it was ECU for sure, heated it and worked normal. Just disassembled and looked for strange joints, and found two pins near connectors, added some solder and now works like new!

Thanks everyone for help
cheers