Newbie needs code help P0684

[myselfnjit]

Hi
I am new to the car and it comes up with a check engine light and code P0684. I have searched for this code and found a little info but would like more if anyone has any.

Where should I start and what should I be testing?

The car is a 2003 Jetta Wagon TDI

Also, is there a recommended book or CD for this car?
thanks

 

[Louis_TDI]

If I'm not mistaken Glow plug and the haynes book is good not the greatest but it's cheap and easy to find.

 

[Curious Chris]

SAE VAG Description P0684 17068 Glow Plug Control Module to PCM Communication Circuit Range/Performance

Check Automatic Glow Time Control Module -J179- Electrical Wiring Diagrams, Troubleshooting &Component Locations

Bentley Manual is the best. Of course I also have the Bentley Factory Service Cd.

 

[jcrews]

Glow plug communication with ECM error. More on that later.

Bentley publishers makes the definitive service manual. There is a book, and a DVD.

I prefer the DVD because it's searchable, can be printed and those pages dirtied up if necessary, etc. The downside is the licensing is not multi-computer friendly and the updates are only good for a limited time now, but that beats no updates at all.

 

[myselfnjit]

I have seen this Glow plug to ECM error in other posts, just dont really know where to start looking. I am brand new to this car and even though I nursed a diesel Volvo back to health, the learning curve it a tad steep. It took me 5 minutes to figure out how to get the battery cover off. Humpf, why is ther a battery cover anyway?

 

[Louis_TDI]

http://pics.tdiclub.com/video/cincitdi/index.html

Look at the 6th video.

 

[myselfnjit]

http://pics.tdiclub.com/video/cincitdi/index.html

Look at the 6th video.

thanks
Seems just like checking on the volvo but much easier access. Since checking the plugs seems easy I will do that 1st.
Any other suggestions are very welcome.

 

[jcrews]

My compiler is busy, but the communication with the module is the problem, not the glow plugs (at least we don't know yet).

When it finishes, I'll pull up the wire diagram to see where you should look. It might be a broken fuse marked 'diesel engine.'

 

[myselfnjit]

My compiler is busy, but the communication with the module is the problem, not the glow plugs (at least we don't know yet).

When it finishes, I'll pull up the wire diagram to see where you should look. It might be a broken fuse marked 'diesel engine.'

OK great
I wont be able to check tonight anyway, so dont rush yourself. I will check tomorrow though.
Thanks

 

[Louis_TDI]

I got one suggestion if you got to change the G.P. get good one's I got bad one's tHis summer and by winter I had to get 4 new ones and change my gp harness

 

[jcrews]

The glow plug relay is in the plenum. Pin 10, marked ST, should be the ECM communication line. It goes to ECM pin 33. The other ECM line goes to pin 9 on both ends and is marked D1.

Start by clearing the code. If it has the intermittent flag, it might have been a one-time thing.

If it returns, check the connection to the glow plug relay. You might have to spray the relay and plug with contact cleaner.

The glow plug relay is located in the plenum, under the rain tray.

Good luck.

 

[myselfnjit]

The glow plug relay is in the plenum. Pin 10, marked ST, should be the ECM communication line. It goes to ECM pin 33. The other ECM line goes to pin 9 on both ends and is marked D1.

Start by clearing the code. If it has the intermittent flag, it might have been a one-time thing.

If it returns, check the connection to the glow plug relay. You might have to spray the relay and plug with contact cleaner.

The glow plug relay is located in the plenum, under the rain tray.

Good luck.

I already tried clearing it. Came back.
I will try to figure out how to get in there tonight.
I will stop at an electronics store for some contact cleaner, any recommendations?
Thanks
By the way, is there another way to clear the codes w/o having a Vag or going to Autozone?

 

[Louis_TDI]

Don't get contact cliner with silicon(all I had) I tried it made it worse

I tried unplugging the bat. for a bit didn't work so I got OBD II for 150$ works great and since it cost my 90$+tax at the dealership it paid it self in less then 2 check engine lights.

 

[myselfnjit]

Can anyone describe how to get into the plenum area to check this relay?

I had a manual coming from ebay and it turns out it is a scan and pdf file. not very user friendly for me.

 

[jcrews]

Remove the star drive screws for the cabin air cleaner, and the air cleaner cover. Remove the wiper arms by removing the nuts, folding the arms to the service position and applying slight downward pressure to the hinge. Then, the arm should lift up off the shaft. The rain tray is press fit on a groove under the windshield and it carefully gets popped off by hand.

 

[myselfnjit]

I have the rain tray off and dont see anything resembling a relay or panel of relays.
I know I sound dumb but I am lost.

 

[Dimitri16V]

Remove the star drive screws for the cabin air cleaner, and the air cleaner cover. Remove the wiper arms by removing the nuts, folding the arms to the service position and applying slight downward pressure to the hinge. Then, the arm should lift up off the shaft. The rain tray is press fit on a groove under the windshield and it carefully gets popped off by hand.

relay in the plenum ? isn't it under that dash in the ALHs ? My PD has it in the plenum

 

[myselfnjit]

I found one relay in the plenum, cleaned it and its socket for the heck of it. its # is 0 281 003 023 on front o38 907 281 A on side

is this the right one?

 

[nocebl]

do a google search for both part numbers and you will know

 

[jcrews]

Yes, it's the correct one. If you can't resolve the problem and the wiring for pins 9/10 checks out, you might have to try replacing it. The current version is 038907281A.

 

[myselfnjit]

tried cleaning the relay and harness, no change
tested all pin sockets in harness for voltage with key on. I dont really know what I am looking for but here is what I found

pin socket labeled ST had no voltage, also pin socket labeled 31 had no voltage. pin socket that matches with D1 had 13volts or so as did 87.

also, the rubber sealing boot inside the harness at the relay end is all bunched up and tearing, making it very hard to reseat the relay to the point of locking with the tab.

does all of this tell me new harness?

also, tested resistance of plugs, all at 1.5 except 1, at 3

 

[Louis_TDI]

No it's vary rare you have to change the relay or the harness you can try closing the pins of the harness with some pliers. Most of the time when the MIL goes on it's just a bit of corrosion between the gp and the harness.

If you really want to check your really hire is how to:

take the ohms option on you multimeter and find the bobbin of you relay this should give you like like 10 to 200 ohms not sure never check this one but at least you fond the bobbin. Now you can tes the relay with the batterie (just make sure there is resistance between the two pins if it's less then like 2 ohms those 2 pins are one of the contacts and if you plug that to the bat you will blow your relay). When you plug the relay to the battery you should hire a click then you can take the beep on your multimiter and check the contacts.

have fun

 

[myselfnjit]

OK here are all of the symptoms/test I have so far

Turn key to on and glow plug light only lights for 1 sec, it is 27F in my garage right now.
MIL reads code P0684
Glow plugs all read 1.5ohms except 1st one, reads about 3
pulled harness to read plugs and it is in pretty sad shape, crumbly and such
cleaned relay in plenum and harness socket, no change
with key in on position, no voltage at glow plugs, fuse on top of battery fine
no voltage (with key at start) at harness D1 or 31 but there is at ST and 87, no idea what this means or if I was supposed to check for this

Where do I go now? I will try pinching down glow plug connections (no voltage anyway though)and harness socket connections but any other help would be great.

 

[jcrews]

31 is ground. Unfortunately the service manual does not explain what the two lines for the ECM are for.

D in the manual refers to the ignition switch, but on the relay could mean something else, like a 1wb for communication.

ST could be a key-at-start signal.

You can get a new seal if you just buy the plug from the dealer, and swap the seals between the plugs.

At this point, a set of glow plugs, glow plug 4 wire harness, and glow plug controller seem to be in order.

I meant to have you disconnect the battery and ECM, and check the wire resistance between the ECM pin and GP box pin. What voltage was at ST?

 

[myselfnjit]

when you say glow plug controller, do you mean the relay that I have in the plenum?

 

[jcrews]

Yup. <

 

[myselfnjit]

ok looks like it is time to spend some money.
I was hoping to only replace one of those things but the harness looks beat and the relay may have gotten wet with that bad seal.

how would I get a part number for that plug?

 

[jcrews]

I can look it up later, or you can call a dealership. Usually the plug part is listed with the relay, but it could be hit-or-miss.

The relay is about $135.

 

[myselfnjit]

Is it ok to use one of the older relay numbers if I can find one cheaper like say ebay? Or should I use the newest number?

 

[jcrews]

It has to be the same type, at least the original part number, but I wouldn't mess with ebay.

1stvwparts, tdiparts, boraparts, bbbb, worldimpex, etc. are your best bet.