99.5 stalling, ECM appears 'dead'

atomic777

Member
Joined
Aug 11, 2004
Location
Santa Monica, CA
TDI
Green 99.5
Hey everyone,

I have a rather troubling problem with my 99.5 jetta tdi.

While driving, for no apparent reason, something seems to short out and the car will die. When the short happens, often i will just get a bit of a hiccup, see the glowplug light for a split-second, and the car will keep going. Usually this is a warning that a bigger stall is coming. Today I was stuck on sunset blvd (not a fun place) for a good 2-3 minutes, trying in vain to start. When I turn the key to the start position, I won't see the glow plug light flash even for a second, and I know the car is not "ready" to start. After waiting a while it will come back and I can start the car again without a problem.

I was lucky to have the car in this 'dead' mode when I got home and hooked my vagcom. Much to my surprise, when the car is in this 'zombie' mode where I don't get the glowplug light indicating that I can start, my VAGCOM can't even get a connection to the ECM, it's as if it's not there. After a while when it comes back to life, I can connect without any issue, and I get no codes other than the cruise control switch problem and the charge pressure/control deviation 17958. (I'm having the symptons of a N75 issue on my car going into limp mode, which have been getting worse in the last week or two. Not sure if it's related though.)

I also checked the sticky on TDI 101 for the anti-shudder valve being stuck, and this is a different issue. My car will crank indefinitely when in this dead mode. Putting the anti-shudder valve into the stuck position still gives me the glowplug light when I put the key into the ignition position, so I know that's okay.

Anyone have any other ideas for things I can check, or is this something I need to take it into the shop for? (Any good mechanics on the LA Westside? :)
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
This is known as a failing 'relay 109' problem. A search will reveal lots of reading on this topic.
 

atomic777

Member
Joined
Aug 11, 2004
Location
Santa Monica, CA
TDI
Green 99.5
MOGOlf thanks so much... you've likely saved me 100's of dollars. With the scare i got today, i'd have gladly paid a lot of money to be certain the problem would go away.
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
:)

Couple of torx screws and the dash pannels come off. The relay pannell is right there.

The new gray relays have the 109 printed upside down compared to the old black ones.

-Jason
 

LNXGUY

Top Post Dawg
Joined
Jan 10, 2004
Location
Barrie, Ont, Canada
TDI
'05 Jetta TDI Wagon
Jason, have you had any probs with your relay 109? *crosses fingers* I got 218,000 miles and mine hasn't done a thing...
 

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
I changed mine at ~130K. I hadn't had any problems, and didn't want to have any :) I had to get an accessory belt from Impex anyway and added a 109 to the order. I took the old one apart and it still looked great inside. I should keep it in the trunk I guess... It's sitting on the table downstairs.

When I took it apart, it looked different inside then the one GeWilli took pictures of. The solder joints looked a little bigger, and the board was shaped different. His golf is a real early 99... mine is a real late 99, so I wonder if there was a partial update at some point?

-Jason
 

atomic777

Member
Joined
Aug 11, 2004
Location
Santa Monica, CA
TDI
Green 99.5
I'm amazed that such a trivial part could do so much damage and be of such poor quality. An inopportune stall could quite possibly get someone killed... for a $20 part. What if my engine died as I was making a left turn on a busy intersection?! This is Hyundai-level quality control, not what I expect from a German car. Not to mention the stupid faulty N75 I have which has reduced my car to a 45hp tractor, I'm basically driving a Lada right now. What good is a bullet-proof engine that will last 500k if I can't rely on a basic relay to keep the ECM powered?!

Sorry, these two stalls today have really soured my mood....
 

ofhs93

Veteran Member
Joined
Apr 4, 2004
Location
Scranton, PA
TDI
Jetta GL, 99.5, Silver
Welcome to the wonderful world of VW electronics....the engineering has always been great...the electrical execusion...well...let's not go there. N75 should not be too difficult to replace...why not just order it with the 109 and git r' done?
 

atomic777

Member
Joined
Aug 11, 2004
Location
Santa Monica, CA
TDI
Green 99.5
Glad to report that I replaced the black 109 relay with a shiny new grey '601' relay, and my car ran for a 30min test drive without any problem.

Not sure if it's my imagination, but the car seems to be running a bit smoother now; appeared to start easier and i wasn't getting as much smoke out the tailpipe going uphill as I used to. Also never went into limp mode and had full power the whole time. Could a nearly-dead 109 have a connection to such problems or is this all in my head? From this thread, http://forums.tdiclub.com/showthread.php?t=31070, it seems this relay is providing power to a lot of pretty critical things, including the N75.

In any case, thanks a bunch to everyone that helped!!
 

bcres978

New member
Joined
Nov 30, 2008
Location
lowell massachusetts
TDI
99.5 vw jetta tdi
Ok I just tried the 109 relay to fix a computer issue my car failed inspection because they said the computer cant read my cars diagnostics so I tried the local autozone ant the OBD-II wont connect either any ideas?
 

MOGolf

Top Post Dawg
Joined
Jun 27, 2001
Location
underneath something
TDI
2001 Golf GLS TDI Reflex silver, rough road suspension and steel skid plate, 2004 Passat Variant, Candy White, rough road suspension and geared balanced shaft module, and much, much more. 2016 LR RR HSE TD6, 2019 Jaguar I-PACE
Blown fuse 12?
 

atomic777

Member
Joined
Aug 11, 2004
Location
Santa Monica, CA
TDI
Green 99.5
Doesn't sound like the issue i had -- the VAGCOM couldn't connect when the relay was cutting out, which prevents the car from running entirely
 

Dave_D

Veteran Member
Joined
Jun 9, 2003
Location
Gaithersburg, MD, USA
TDI
2015 Passat Titanium Beige six speed manual & Jetta, 1999.5, Tornado Red
bcres978 said:
Ok I just tried the 109 relay to fix a computer issue my car failed inspection because they said the computer cant read my cars diagnostics so I tried the local autozone ant the OBD-II wont connect either any ideas?
Do you have an aftermarket radio/deck in the car? If so, you need to check the wiring. You can verify this is the problem by disconnecting the radio/deck and seeing if you can connect with VAG-COM/OBD-II then.

Dave
 
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