01 Jetta starts & immediately stalls. - intermittent problem

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
Hey guys, I'm having an intermittent problem with my 2001 Jetta. (185K miles)

I'm pretty sure it's electrical, but not positive.

Sometimes it starts up and then immediately stalls. Just about as soon as it gets to full idle speed, (about 1 second) it just shuts back off, like i turned off the key. Sometimes the security light flashes (the little car with the key icon in the gauge cluster) when it stalls. Sometimes not.

It seems to happen more often when it's wet out. I tried different keys. One works better than the other, but they both have the problem.

Once it's running, no problems at all.

A guy at the VW parts counter seemed to think it might possibly be the gauge cluster. Says those are classic symptoms of gauge cluster problems. I thought it might be related to the anti-theft key coding, due to the anti-theft light flashing, but i don't know.

Anyone know what might be causing this?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
You will need to get the codes read so that we can help you more.

It does sound like it is the immobilizer, but codes will help us diagnose what is causing the problem.

Sometimes odd electrical issues can be resolved by taking the cables off the battery and touching the ends together for 10-15 seconds and then hooking the battery back up.

Also, you say some keys work "better" than others. Does one key not work? If the key is not correctly programmed for your car then that would trigger the immobilizer when you try to start it without disarming the lock.

It's all guesswork until we get the codes (and maybe even then :) )
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
The CEL is not on, so i didn't think there would be any codes. I'll check tonight when i get home.

shorting the battery leads together? that sounds a little risky.

No, they both still work. last week was the first time i noticed the immobilizer light flashing, so i thought it might be a bad key, so i decided to number the keys, and see if i could tell any difference between them. on saturday (a rainy day) key #1 caused the car to stall about 4 times in a row (with immobilizer light flashing) I gave up, and tried key #2. Key #2 stalled once (no immobilizer light), but then kept running the second try. But, I have used both keys succesfully since then, with no stalling on either one. I haven't been able to develop a consistent pattern with either key, so i'm not sure it's the key. Both keys are original to the car, and are not recently programmed.


How does the immobilizer work 'normally' on a TDI if someone uses an incorrectly programmed key? would it start then immediately stall, or does it not crank at all, or would it crank, but not start?

I'll check the codes tonight.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
mike944 said:
The CEL is not on, so i didn't think there would be any codes. I'll check tonight when i get home.
It is pretty much gaurenteed that there will be codes. There is absolutely no reason why the CEL has to be on for there to be codes.

mike944 said:
shorting the battery leads together? that sounds a little risky.
without having them connected to the battery, hopefully you saw that part. All you will be doing is discharging latent energy from the car, there is no powersource connected, so why would it be risky?

mike944 said:
How does the immobilizer work 'normally' on a TDI if someone uses an incorrectly programmed key? would it start then immediately stall, or does it not crank at all, or would it crank, but not start?
If someone tried to force the car to start without disengaging the alarm the immobilizer would kick in. You can also see the immobilizer kick in when you have electric charge issues, that goes back to my comment above telling you to touch the battery cables together.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
puter said:
....
without having them connected to the battery, hopefully you saw that part. All you will be doing is discharging latent energy from the car, there is no powersource connected, so why would it be risky?
I saw that part, don't worry. I guess that some of the modules might have capacitors in them specifically to maintain power when the battery gets disconnected, and shorting them together would force-discharge them, negating their entire purpose. That's why i thought it might be risky. shorting the cables together is just not something you're 'supposed' to do. it doesn't seem like the 'right way' to fix anything. And with a car full of a lot of expensive electronics, it seems like a big risk to my wallet.

I'd like to save that as a last-resort option.

I'll read the codes on the immobilizer and see what i find.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
That is a common option, and a common solution.

I would advise you to do it.

Also, capacitors have a limited amount of energy storage. If this were going to damage your car by having them discharge, then you would find that your car would be quickly damaged when your battery dies. You can argue with me on this if you want, but I have a degree in the area :)

At this point, if you are unwilling to try resetting the electronics as instructed, then I am not sure I can help you...I don't want to go down a long troubleshooting course when all you had to do was that.

If you do not believe me, then I suggest you use the search link at the top of the page and research for yourself whether or not it is a viable solution.
 

runonbeer

Maintenance EnthusiastVendor
Joined
Apr 15, 2002
Location
Austin, TX/Chapel Hill, NC
TDI
'00 Golf 02M, '10 Golf 02E, '02 UTE 02M
I had an immo issue on my car recently (disconnected battery, pulled ecu, took ecu to colorado, chipped it, brought it back, put it in).

All I ended up having to do was disconnect the battery again and cycle the key. then reconnect the battery and everything worked.

On my car I also had to recode the ecu to my cluster but since you haven't messed with yours, then you will most likely not have to do this.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
Well, there definitely were codes. Just as i suspected, it looks like it's got something to do with the immobilizer.

No codes from the immobilizer itself, but i got the following codes from the engine & instrument cluster.

Engine codes:
17978 - Engine Start Blocked By Immobilizer - P1570 - 35-10 - - - Intermittent


Instrument codes:
01039 - Coolant Temperature Sensor (G2) - 30-10 - Open or Short to Plus - Intermittent

01176 - Key - 07-10 - Signal too Low - Intermittent

-----------------------------------------------------------------------

I find it strange that the coolant temperature sensor code appears in the instruments, and not in the engine codes. Perhaps it's related, perhaps it's a fluke.

I did not reset the codes.

I guess i can try the cable shorting thing. I won't question your degree. I have a mechanical engineering degree, which means i know just enough about electronics to be dangerous, but not enough to actually know what i'm doing. All i can do is question things when they sound strange, or bad.

Should i try the cable shorting thing now, or should i do more testing first based on the codes i recieved?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
It won't hurt to try. I've done it numerous times with no harm and have heard of it fixing this sort of issue.

Either it'll fix it or things will stay the same. Good luck.

. o O (my degree doesn't make me think it will fix this...just that it won't hurt your car :) , your degree is much more helpful in terms of actually fixing a car =P )
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
I noticed something this morning, related. While i was waiting for the glow plugs this morning, i noticed the immobilizer light flashing, before i even tried to start the car. i removed the key, re-inserted the same key, and turned it on again, and no immobilizer light. (it was dry today)


ok, i'll try the cable shorting thing tonight.

Do those codes tell you anything about the issue?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
not me personally, there are others here who it may.

I would double check how tight your cables are on the battery. Anytime I see sensors going bad and strange behavior I suspect loose cables on the battery.

When you put them back on make sure you get a good connection.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
puter said:
I would double check how tight your cables are on the battery. Anytime I see sensors going bad and strange behavior I suspect loose cables on the battery.
When you put them back on make sure you get a good connection.
__. And grounds; they're important, too.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
ya, the only reason I didn't say grounds was because usually when there is a grounding issue I see short to negative, not short to positive. But it's definitely always a good idea to check the grounds when you are having electrical issues; especially the one under the battery, it seems to be problematic.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I agree that all 3 grounding points under the battery are often problematic.

This looks as if it could be a wiring issue in the ECM wiring harness. I would inspect the harness for chafed wires (bare wires) and the connectors for clean tight fits, if the problem persists.

The Coolant temperature sensor could be a totally separate failure, or it could be related. The CTS fail often enough that I would just replace the sensor, if it were my car.

Then if the code reappeared I would inspect the wiring harness for wires that have the insulation chafed off of them.
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
DanG144 said:
I agree that all 3 grounding points under the battery are often problematic.

This looks as if it could be a wiring issue in the ECM wiring harness. I would inspect the harness for chafed wires (bare wires) and the connectors for clean tight fits, if the problem persists.

The Coolant temperature sensor could be a totally separate failure, or it could be related. The CTS fail often enough that I would just replace the sensor, if it were my car.

Then if the code reappeared I would inspect the wiring harness for wires that have the insulation chafed off of them.
I still think he should try touching the bat. cables together before he goes into all that. It's easier and it could resolve the problem.

I have never heard of a single negative effect from doing that. If anyone has any to volunteer, feel free.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
puter said:
I still think he should try touching the bat. cables together before he goes into all that. It's easier and it could resolve the problem.
(Snip)
__. Yeah, I agree that that's the first thing to try. But it's starting to sound to me as if he has an intermittent connection and the immobilizer function in the "cluster" is having to boot up often -- when this happens he gets the "fault" symptom. But "clear with the two terminals" is def. the first place.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
I'll try it tonight. I'll take a look at ground connections, i know those can be problematic on any car, and cause a whole host of electrical problems.

Per DanG144's comment above, i'd like to inspect the "ECM wiring harness" can anyone tell me where it's located, or specific areas that typically get chaffed?

The coolant temperature sensor code is odd. Why would this code appear in the instruments, and not the engine? I do have a spare sensor, and can change it. I'm due for a coolant flush anyway. I'll do it at the same time as the coolant flush, but that probably won't be for a couple of months. I don't think it's related to the imobilizer problem, but it could be a warning sign of a bad ground.
 
Last edited:

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
you don't need to flush the coolant unless it has become contaminated for some reason. I don't think the temp switch would keep the car from running after it's started.

the 1st thing to try is touching the two primary battery wires
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
The CTS has two sensors in one unit. One feeds the ECU/ECM, the other feeds the instrument cluster.

The ECM/ECU is located in the plenum under the winshield wipers. The harness runs in the plenum to the left side of the car, where it exits to the engine compartment, and then goes to the engine and the cabin. The Immobilizer is inside the cabin in the instrument cluster.

I have not been able to learn much about how they communicate, or which wires they communicate on. I suspect this information may purposefully be a bit closeheld.

If anyone can shed more light, I am always willing to learn.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
Well, i'm officially screwed. it's stopped working completely. Fortunately....i was home when it decided to quit. I was able to do a temporary immobilizer bypass using VAG-com & the SKC to get it into the garage.

I tried shorting the cables together, and nothing. I cleaned ALL the grounds in the engine compartment, including the ones up by the ECM. No change. still dead.

I guess tommorow's task is to check the connection on the back of the instrument cluster.

Is there any way to determine if it's a faulty instrument cluster? how bad is that going to hurt? $$$ Can i even do it myself, or am i stuck at the dealer's mercy?

Any other suggestions?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
Have we had you check for coolant migration?

Also, make sure those grounds are _tight_.

It may be worth taking a multimeter and checking the resistance on all the cables to make sure there are no breaks, especially on the ground from the battery.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
I *think* i removed the coolant sensor seal a few years ago to prevent migration, but i'll check.

They are all tight, i torqued them all to spec.

I can try checking resistances. I'll also check the resistance of the antenna loop around the key cylinder for breaks.

If i have the 4-digit SKC, can i replace the cluster myself? anyone know how much one might cost?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
I don't think you should jump to replacing the cluster quite yet.

I've never heard or removing a seal to prevent migration, we always drill a hole in the bottom of the connector on the tank so that any coolant that seeps up just drains out.
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
I'm not jumping to that quite yet, but i'm trying to assess the situation and come up with the worst-case scenario.

Removing the seal accomplishes the same thing as the hole. It breaks the sealed cavity, and allows any leaked coolant in to the connector cavity to vent to the outside, and not get forced up through the wiring harness under pressure.

Just ran downstairs and checked it. (i'm telecommuting today) Looks like i didn't remove the seal, but i cut a small piece out of it to accomplish the same thing. regardless, the whole cavity is bone dry, so it's not coolant migration.

I've been reading about the immobilizer antenna in the lock housing. any way to check that? I was thinking of making up a coil of wire, holding it concentric with to the lock cylinder, and hooking it to an oscilloscope, and looking for signs of communication. Obviously, i can't read the communication, but i should at least be able to tell if any communication is going on. Sound like a plan?
 

puter

Top Post Dawg
Joined
Jun 19, 2007
Location
Tacoma, Washington
TDI
2002 Jetta GLS
How sensitive an o-scope do you have? I'm guessing it would be pretty small variations that you would see. Inductive power is not necessarily very strong :) Make sure you use lots of wraps.

I wish I had an O-scope :/
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
nothing out of the ordinary, but it picks up pretty small changes. it's worth a shot.

I only got this one about a month ago. never had one before that. picked it up from a surplus store for $30. couldn't pass it up.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Mike, If I was in your shoes, I would seriously consider mailing my ECU off to Jeff of Rocketchip, for an immobilizer delete. I would get an RC1+ tune while I was at it.

Do you have the Bentley CD repair manual? It has a little bit of immobilizer overview in it. I have never found out which wire the signal travels on, so I do not know the color or size or anything else about it.

Dan
 

mike944

Veteran Member
Joined
Aug 18, 2004
Location
Vernon, Ct
TDI
2004 Jetta
that's an interesting idea. i didn't know that was possible. If i do that, will the immobilizer light on the dash flash forever?

i've always wanted to add a remote start, but with the immobilizer, it was impractical. this might be the answer to both problems.

I did some research, and Jeff seems to be difficult to get ahold of. this is my primary car, and i would need it done fairly quickly. I can't really play email tag with somebody. Anyone know a reliable way to get ahold of him?
 
Top