# Bad Crank Sensor, does it ALWAYS throw a code?



## stratocaster (Jul 13, 2004)

I have another post in this forum about my GLI not starting. I've checked everything I can think of to find the culprit, but everything seems to check out fine somehow.

My question is, has anyone ever had a crank sensor go bad on them and not throw a CEL or just a code in general? From what I understand so far, they almost always throw a code when they go out. I'm just trying to rule it out as a possible culprit.


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## veedub-less (Dec 18, 2007)

can't answer your question because i don't know for sure. but have you tried hooking up a scanner to it yet? reason i ask is because i had a problem where suddenly my car wouldn't start. it would crank but not start. i hooked up vag-com and it couldn't detect the ECU either. my problem turned out to be the ECU relay. it went bad and the ECU wasn't getting power. replaced it and all was good.


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## bootymac (Apr 19, 2005)

Mine didn't trigger the CEL, but a fault code was stored


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## stratocaster (Jul 13, 2004)

veedub-less said:


> can't answer your question because i don't know for sure. but have you tried hooking up a scanner to it yet? reason i ask is because i had a problem where suddenly my car wouldn't start. it would crank but not start. i hooked up vag-com and it couldn't detect the ECU either. my problem turned out to be the ECU relay. it went bad and the ECU wasn't getting power. replaced it and all was good.


I've hooked up a little generic OBDII scanner, but the only code was "IAT sensor high input". I pulled the sensor and cleaned it with electrical cleaner and put it back in. The code didn't come back, but it didn't fix my problem at all. I've checked just about EVERYTHING other than the ECU relay, so I'm very glad that you mentioned that. 

I know that the ECU fuse is ok, but that of course doesn't necessarily mean that the relay is fine as well, especially if it is wired after the fuse in the circuit. Unfortunately I don't have the scanner anymore and I'm not sure if it detected the ECU or not. Did it have any additional codes stored that were related to the bad relay? And did you test the relay a certain way to determine if it was bad, or did you just replace it and it worked?


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## salz2135 (Sep 18, 2006)

On friday, I had an S6 that wasn't starting. Fuel pump would not run when the engine was cranking. Fuel pump relay was ok and the pump would start when jumped from the relay panel. Traced the problem back to a damaged wiring harness for the crank position sensor where it had rubbed against the Bank2 combi valve. 

There was no CEL and no stored fault. 

Hope that helps.:beer:


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## Space9888 (Mar 18, 2002)

in my experience, usually believe it or not the crank sensor fault gets triggered when the fuel pump fails. you can determine if its the fuel pump by disconnecting a vaccum line and spraying a small puff of starting fluid into the vaccum line with the straw that comes with the starting fluid (usually). if its the fuel pump the car will fire run and stall out.


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## Space9888 (Mar 18, 2002)

if its the a relay or ecu issue usually you will have multiple power supply related faults


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## Space9888 (Mar 18, 2002)

you will need vag software in order to determine the root cause if it is a crank sensor issue, generic code readers usually dont cross over to the actual vag related faults. if the crank sensor is the fualt you should get a correlating fault.


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## veedub-less (Dec 18, 2007)

Space9888 said:


> if its the a relay or ecu issue usually you will have multiple power supply related faults


when my relay went, i couldn't even connect to the ecu, thus not giving any faults.


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## afullquiver (Apr 22, 2009)

I can't remember what codes I had, I think I actually had a code that was related to the Cam Position Sensor or some correlation fault between Crank and Cam like Space9888 posted above. Basically I understood it as the ECU saying I can't figure out timing between the Crank and the Cam so you are going to have to sit here a while. Perhaps someone on here can provide more info.

When mine was acting up my symptoms where as follows:

Intermittent starting, stalling and then warm start problems.

I noticed watching the tach while cranking, some times the tach didn't move. When the car was about ready to start, the tach would bounce up to about 500 then if I cranked it a time or two it would usually start. I am not a VW guru, just reporting my symptoms and observations. It is a PITA to change, but I have not had a single problem with starting since I change my 1.5 years ago.


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## stratocaster (Jul 13, 2004)

I don't think it's the fuel pump at all. I've tested for power at the pump connector and I had 12v with the key on and while it was cranking. I also have plenty of fuel in the fuel rail after the pump primes. Also, this problem happened with one turn of the key. It never showed ANY sign of problems, then I shut it off and tried to start it again and it hasn't started since. 

I'm suspecting a bad ground at this point. It has to be something electrical for it to just stop working with one turn of the key. I've never heard of a fuel pump just quitting and never working again when it was working perfectly 60 seconds prior. I mean, if it was going out, it should at least try to start and die a few times, or work intermittently for a while before it goes out completely. Also, I should mention that when I shut it off that time, the battery was suddenly completely dead when I tried to start it again. The battery was old so i assumed it had a dead cell. One new battery later, car has plenty of power but still won't start. That's what makes me pretty sure that it's something electrical.

Maybe something shorted out, or a ground got some crap on it, or maybe a sensor just took a dump. I've checked just about everything. I'm a mechanic by trade, so I know about and have already checked all of the obvious things like fuses, battery voltage, gas level, spark from the plugs, etc. I just don't have enough time to put into it right now to really dig in and figure this out. Everything checks out so far, that's whats so annoying about it. I have a feeling I'm gonna end up chasing down a bad wire or something like that. I HATE electrical problems! :thumbdown:


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## Andaloons (Apr 16, 2004)

afullquiver said:


> I can't remember what codes I had, I think I actually had a code that was related to the Cam Position Sensor or some correlation fault between Crank and Cam like Space9888 posted above. Basically I understood it as the ECU saying I can't figure out timing between the Crank and the Cam so you are going to have to sit here a while. Perhaps someone on here can provide more info.
> 
> When mine was acting up my symptoms where as follows:
> 
> ...


I had almost the same exact experience when mine started to fail. :thumbup:


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## Space9888 (Mar 18, 2002)

did you figure it out yet?


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## stratocaster (Jul 13, 2004)

Unfortunately no. I fix cars out of my garage right now while I'm in between jobs and I had to leave my car alone for a bit and get some other cars done. Gotta get some cash comin in just in case my car ends up costing me a little more than I'm hoping it will. 

I'm really to the point where I'm not going to be able to figure out the problem unless I get a VAG-COM rather than the cheap OBDII scan tool I've been limited to. The other option is to just start guessing and throwing new parts at it, which is something I refuse to do for many obvious reasons. Im fairly confident that I could easily solve the problem with a VAG, or at least some kind of high end scanner, like a Snap-On Solus or something similar.

I've checked just about everything that I can think of to check in a situation like this, and everything seems to be in working order (except the whole starting problem....). Not to sound like a broken record, but it pretty much has to be something electrical. Its rare that a car works perfectly fine, without showing a single sign of failure on any front, and then suddenly stops working after one turn of the key as far as mechanical failure goes. Most of the common causes of a no start problem like I've got will almost always start out as an intermittent problem before they completely die. That, and the fact that the battery had instantly gone dead when the problem started also points to something electrical. 

The main question here is what kind of problem would cause a battery to go completely dead in 2 minutes, and cause a no-start issue along with it. Keep in mind that the battery was getting to the point of needing to be replaced, but it still started every time without fail before the problem started, even in cold weather. The alternator is the first thing that came to my mind, but the alternator tested ok.


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## Jmhockey1920 (Aug 12, 2010)

I'm currently having the same problem with my 2002 Jetta. I changed the fuel filter, and new spark plugs. It has to be something electrical to just cause this problems. I found a website yesterday that has over 90 posts of people having the same problem. If you find out the problem, please let me know.


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## xXGti2006Xx (Feb 14, 2006)

bump this same issue im having!! I have a walboro 255 inline but i dont think it would randomly not work? I think its my CPS but got no codes?


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## All_Euro (Jul 20, 2008)

I've been getting the odd crank position sensor code and starting issues too but today I was driving home and my car just died... started pretty quick so I drove home with the EPC light on 

Like you guys, I'd really like to know what's going on before replacing anything... BUMP!


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## saps (Jul 10, 2009)

always is a dirty word when figuring out automotive problems. The crank sensor is a very important input sensor and will not run without it.


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## Andaloons (Apr 16, 2004)

saps said:


> always is a dirty word when figuring out automotive problems. The crank sensor is a very important input sensor and will not run without it.


^^^This ^^^

Crank position sensor. Change it!!


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