Limp mode when turning off cruse control.

Forcefed TDI

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Nov 19, 2017
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New Mexico
TDI
Jetta
When I drive to work I'm on the highway doing about 80mph. Twice this has happened now, that when I turn the cruse control off the car goes into limp mode. Both times it has happened when the car is accelerating. I checked vagcom for codes and nothing. I replace the air filter, fuel filter, and used diesel purge. I also cleaned the battery grounds under the battery box, checked the MAF, and went through all the vaccum lines. Any ideas on what could be causing this to happen? This has never happened before and now it's twice in 3 days. Nothing else is wrong with the car and I'm still averaging 48 mpg. This is in a 2002 Jetta TDI.
 
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Nevada_TDI

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Aug 17, 2008
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2001 Jetta TDI
Do you turn the cruise control off at the turn signal stem, or do you turn it off by using the clutch and/or brake pedal? I don't know if it might make a difference or not, the thought just crossed my mind to ask you this question.
 

Forcefed TDI

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New Mexico
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Jetta
Both times I used the brake to shut it off because of traffic. I did try using the switch on my drive to see if it would have the same result, but it didn't. It just turned off the curse control and the car was fine. It's really hit and miss. My drive to work is 122 miles and it has only done it in the morning. The drive home has no problem, so far. It's not a big deal, just wanting to know if anyone has had this problem.
 

UhOh

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Any codes when scanning? Sounds like the brake activation switch might be the source.
 

Nevada_TDI

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Reno, sort of...
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2001 Jetta TDI
If I read you right, the turn signal stem switch does not cause the problem but the brake switch does? Can you get access to VCDS?, it will tell you what the switch is actually doing. There may be some conflict that is caused by the interaction between the switch on the brake pedal and the clutch switch as well.
 

gearheadgrrrl

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'15 Golf DSG, '13 JSW DSG surrendered to VW, '03 Golf 2 door manual
Can you provoke limp mode with the cruise off, say with full throttle acceleration? Before I installed ID Parts limp mode fix kit and cleaned the intake manifold full throttle at over 2400 RPM would trigger limp mode. But it would never trigger limp mode with the cruise on, I suspect the cruise control overrides limp mode initiation.
 

wonneber

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Monroe, NY, USA
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2014 Jetta Sportwagon,2003 Jetta 261K Sold but not forgotten
Twice this has happened now, that when I turn the cruse control off the car goes into limp mode. Both times it has happened when the car is accelerating. I checked vagcom for codes and nothing.
Did you scan for codes when it happened and before shutting the car off?
Shutting the car will clear the codes.
I was getting good at going down the highway, putting the can in neutral, shutting it off (DO NOT REMOVE THE KEY), waiting 5 seconds, starting it again and then back in 5th.
Limp mode over. :)
 

Forcefed TDI

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New Mexico
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Jetta
I checked Vagcom and looked, no codes. It only seems to happen with the brake switch, and I looked at that and didn't find anything. I have noticed that when it does happen the car is accelerating kinda hard, like going up a hill. I have been using the the switch on the turn signal with no problems. I don't know why, but it seems to only happen in the early morning, I can't get it to do it in the afternoon. I think my next item to look at will be carbon build up in the intake and egr. I do have a bit of oil on the egr, nothing crazy but some. The car has 198,000 on it. Also, to answer a question, no I can't get it to go into limp mode by accelerating and cutting the throttle. I will be also looking at the wiring to the brake switch to see if anything is wrong. The only code I show is for my passenger door, the mico switch is not showing the door closed. I plan on fixing that soon, but I don't think that would cause a problem.
 

Nevada_TDI

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Reno, sort of...
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2001 Jetta TDI
There may not be codes in VCDS but there are readiness codes available; what I mean is with VCDS hooked up you can check the clutch switch and brake switch in VCDS. I don't remember which Group it is in, but the boxes contain only binary 0's and 1's, and when you move the brake or clutch the numbers change accordingly.
 

P2B

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Toronto & Muskoka, Canada
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2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
I checked Vagcom and looked, no codes. It only seems to happen with the brake switch, and I looked at that and didn't find anything.
Are you sure it's limp mode? - it really should set an overboost or underboost code if so.

Limp mode occurs when there is a significant discrepancy between requested and actual boost for an extended period of time - based on looking at logs, I think it's 300 mBar or more for 5 seconds. When the ECU sees this condition, it assumes something is wrong with the turbo control system and reduces fueling to prevent turbo damage. As far as I know, this is the only condition which will trigger limp mode.

Simon
 

UhOh

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2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
^^^ Um, yeah. OP, what is the actual behavior of the car when it encounters what you are calling "limp mode?"

My car's cruise/speed control started dropping out on me shortly after I got it. It would happen as I was going up slight inclines. No CEL (didn't have VCDS at the time, so no idea if any codes were set, though when I eventually got VCDS it didn't show any codes). This issue cleared up after I cleaned the intake and EGR valve.
 

Forcefed TDI

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New Mexico
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Jetta
So I messed around looking at the wiring and everything looked fine. I had it go into limp mode a couple times last week. I tried today to get it to do it again, and nothing. I will look at everything this weekend and get back to you guys. I will continue to try and get it to go into limp mode this week to try give you better information on when it happens. Right now it seems fine. This started after I did a air filter change, oil change, and fuel filter change with diesel purge. I wouldn't think this would cause a problem, but thought I would let everyone know.
 

UhOh

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2000 & 2003 Golf GLS (2005 Mercedes E320 CDI)
IS this really Limp Mode? (please, when someone asks a question answer it) When you get this condition does turning off the engine and restarting resolve it (until next occurrence)?

Did you disconnect the vacuum line to the air filter box? (I tend to pull the box out and clean when I refresh the filter; this requires disconnecting the vacuum line.) While a disconnected line in and of itself cause a problem, sucking in crap through it to the N75 CAN.
 

Forcefed TDI

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New Mexico
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Jetta
UhOh, I have noticed that I have not had the problem this week, and I think I know why. The week this started I had done a air filter change and other maintenance. When I had pulled the air filter out I took the top of the box off and disconnected the MAF. I put everything back and drove it to work. That is when the car would go into limp mode, and I would have to pull over and restart the car to get the power back. After that week I pulled it apart on the weekend, and didn't find anything wrong. But, I did unplug the MAF and put dielectric grease on it. Since I did that I have had no problems, and I have been trying to get it to do it again, and nothing. So, would a bad connection with the MAF not throw a code and do this? I think I'm on the right track with this, but just want to know. So far the car has been running great all week, and I use cruse control a lot. My trip to work is 122 miles highway. I still plan to pull the egr and intake apart just waiting on parts.
 

Vince Waldon

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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
If we're going to help, we really really really need to know what *you* mean when you say "limp mode", 'cause it seems to mean different things to different people. :)

Perhaps the easiest way is to describe your exact symptoms *without* using the phrase "limp mode". What does the engine do, what does the turbo do, any signs on the cluster, what do you do next when this happens, how does the car respond. Sorta like that? :) :)
 
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UhOh

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UhOh, I have noticed that I have not had the problem this week, and I think I know why. The week this started I had done a air filter change and other maintenance. When I had pulled the air filter out I took the top of the box off and disconnected the MAF. I put everything back and drove it to work. That is when the car would go into limp mode, and I would have to pull over and restart the car to get the power back. After that week I pulled it apart on the weekend, and didn't find anything wrong. But, I did unplug the MAF and put dielectric grease on it. Since I did that I have had no problems, and I have been trying to get it to do it again, and nothing. So, would a bad connection with the MAF not throw a code and do this? I think I'm on the right track with this, but just want to know. So far the car has been running great all week, and I use cruse control a lot. My trip to work is 122 miles highway. I still plan to pull the egr and intake apart just waiting on parts.
OK, so this does sound like Limp Mode (a restart clears it up).

MAF issues don't appear without some sort of code. It might be more of a coincidence that manipulating the MAF connection appeared to make a difference. Unless a MAF is really crapped out it won't trigger a code: car will just be lower in performance, though not limp mode low.

Son's Golf once hit limp mode, following a tune. It's been maybe 1 1/2 years now and, without having changed anything, there's been no further occurrence.

If it's an intermittent issue then one will have to keep track of several things that might contribute: driving situation, how the car is being commanded; weather (temps, humidity) etc...
 

Forcefed TDI

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Jetta
I know the MAF didn't crap out, because my last Jetta had a bad MAF and I know how the car responds when it goes out. Just thought a bad connection could be the problem.
Let me explain what happens when this problem occurs. I put the car on cruse control at about 82 mph. As I'm driving along the road a car may pull out in front of me and I will tap the brake to cut the cruise and slow down. Every now and then when I cut the cruse control the car will suddenly have no power. I have maybe 20% of my throttle. I can put it to the floor and just barely be accelerating. I can maintain a decent speed but the second I go up a hill it goes down to 40 mph. I then have to turn the car off and restart it, after that it's back to normal. This has happened at random times and in different places but all while on the highway above 65 mph. This has not happened in town, and only seems to happen when I have been driving for about an hour. No codes show up and the car runs great. Weather has been around the 30's when this has happened. This week I have been trying to get it to do it again, and finally I it did it this morning. I happened when I was accelerating up a hill and a car pulled out. I tapped the brake and went to apply more throttle to pace the car and noticed I had nothing. I didn't notice anything strange about the car when it happened it was just like someone hit a switch and cut my throttle. If I put down 15% throttle I could feel the motor trying to go. Anything after 20% I had nothing. So I just turned the car off and restarted it. Just like that the car was back to normal. I hope this helps you guys out. Just a strange thing to happen that I couldn't figure out.
 

BobnOH

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central Ohio
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New Beetle 2003 manual
Having spent too much time reading these forums, I have seen the cruise not working because of the MAF. But not the other way around. If it does the same with the MAF unplugged, MAF is O.K. (if it clears up without the MAF it could be the issue).
You're on the right track, connections, you might research w/wire diagrams anything that sends signal to the TPS. Could be something crazy like a brake light switch
So what you get is not so much limp as no power.
 
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Vince Waldon

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Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
Have you ever tried disabling the cruise by turning it off as opposed to tapping the brakes?

Would be good to know if it's specifically a brake switch-triggered situation.. in particular, a malfunctioning brake switch can cause the ECU to de-fuel.
 

P2B

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I know the MAF didn't crap out, because my last Jetta had a bad MAF and I know how the car responds when it goes out.
MAFs have several failure modes, which can produce a variety of symptoms. You can't really rule out the MAF based on past experience, better to log requested versus actual air flow to determine MAF health.

Simon
 

wonneber

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Have you ever tried disabling the cruise by turning it off as opposed to tapping the brakes?
Would be good to know if it's specifically a brake switch-triggered situation.. in particular, a malfunctioning brake switch can cause the ECU to de-fuel.
I wonder if taping the cruse switch to disable it instead of shutting it off would show the same result.
The resume speed would still be set.
:confused:
 

Forcefed TDI

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New Mexico
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Jetta
I have used the switch to turn it off and have not had it trip yet. I'm going to run some logs and see what I get. The only problem is that I have had times that it doesn't happen for 4 days, then out of no where it hits and I'm having to restart the car. This will be put on hold for a couple weeks since I have to go out of town for work. When I get back I should have some logs and the intake and egr cleaned. I will also check the turbo for shaft play just for the hell of it. I may even replace the brake switch just because it's only 12 bucks. I'll let you guys know how it goes when I get back.
 

Vince Waldon

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If the ECU thinks the accelerator and brakes are being applied at the same time it will defuel... which I suppose it might think if the brake light side of the brake switch was working but the "defeat the cruise control" side wasn't.

VCDS can show you the status of both sides of the switch independently, as you depress the pedal.

Long shot, admittedly, but this is a weird one. :)
 

Vince Waldon

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Yup.

If this is the case, pumping the accelerator pedal a couple times should bring it back to its senses as it's programmed to eventually pay attention to the pedal again.

Worth trying the next time just to rule out as a suspect if nothing else.
 

Forcefed TDI

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Jetta
I'm back! Okay so I did try the pumping accelerator a couple time and did not work. I got back Friday and Saturday took the car out. I was driving it home doing about 75mph, when I need to pass a car to take the exit. I rolled on the throttle, got passed them let off and boom, limp mode. I tried the accelerator pumping for a bit, and nothing. This was the first time I have got this thing to do this, so I guess the cruse control was not the problem, it was the sudden let off of power. I turned it off and on again, and back to normal. Sunday, I removed the intake and cleaned it. I also removed the EGR, and cooler. After that I took the car out for a drive and it runs better, but I noticed my brakes work wayyyy better. I am wondering if I had a small vacuum leak that had been causing this. When I removed the EGR I also remove the ASV and cooler. Plus, did a reroute of the vaccum lines, cleaning it up. I tried multiple times on my way to work today to get it to go into limp mode and the car just ran fine. I have a lot more power and I don't have the small hesitation like before. I did the EGR delete kit from Wolfsburg with the race pipe. I cleaned the intake manifold too, lots of carbon and gunk in it, but not too bad.
 

mrfiat

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Mar 24, 2008
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Los Ranchos, NM
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I really think you should do your turbo boost graph using the Vagcom. If you are over-boosting it would trigger limp mode. Usually there would be a CEL code though.

What part of NM are you in? I'm in Albuquerque.
 

Forcefed TDI

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Jetta
I'm in Los Lunas, really don't have time during the week since I work at Los Alamos Labs. The commute kills my free time. I'll graph it out this weekend. Just busy this week. Plus, didn't have time to run a log Sunday. I checked the turbo too when I did the work. Didn't have no play.
 

Forcefed TDI

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New Mexico
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Jetta
Just to give a update. I ended up finding a a crack on the vacuum pump to brake booster line. I didn't notice it had tape on it. Once I removed the tape I found the crack. I think this has been the problem the whole time, and why it was so random. So far I have had no problems.
 
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