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Old 04-05-2012, 10:35 PM
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Question Coolant Temperature Sensor? 1999 1.8T, AEB

For a year or so now, I've had a crank but no start problem. If I run the car for a short trip of 5 - 10 minutes, when I try to re-start it cranks but doesn't start. It will start after letting it sit for about 20 minutes. I read the forums and checked the basics - spark, fuel, air/vacuum, etc. VAG-COM showed no codes. Then I read something about the crank position sensor and the coolant temperature sensor. So the next time it happened, I didn't have my VAG-COM so I just unplugged the coolant temperature sensor and it started up after gurgling for a second or two. Is there any way to check the coolant temperature sensor itself? I know a new one with the clip and gasket is pretty cheap, but I don't like taking random guesses and throwing parts at a problem until I get lucky and fix it. Thanks for any help!

Pete
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Old 04-06-2012, 08:51 AM
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I've never tried it, but I would think you'd be able to do an output test with Vag-Com. I'm not terribly familiar with it, maybe one of the guys who uses it more often can confirm.
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Old 04-06-2012, 10:40 AM
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In VAG-COM you can read out the temperature the CTS is sending to the ECU. There are 2 ways to do it: when in VAG-COM, first select Engine to access the ECU, then either click Measuring Blocks or Advanced Measuring Values. Either way you'll be able to find out the status of the CTS.

When the car is at operating temperature, if the value reported by VAG-COM isn't about 80-90 deg. C then there's definitely an issue with the CTS.
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Old 04-06-2012, 01:21 PM
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^Exactly who I was hoping would chime in
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Old 04-06-2012, 01:57 PM
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Thumbs up Thanks!

Thanks Metal Man and CCA4! It may take a few days to get to this, but I'll give it a try and post how it goes. I know the basics of VAG-COM, but I'm glad there are people to help with the finer details.

Pete
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  #6  
Old 04-09-2012, 10:47 AM
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Question Not the CTS. May be a battery / parasitic draw issue.

I had a chance to test the CTS this weekend, and it looked to be in good working order. I also had a crank but no start condition this weekend when I drove about 5 minutes to the gas station. No luck this time when removing the CTS. The car did start when jump started, which was surprising to me.

The starter was cranking fine without any hesitation or dying, so it didn't seem that the batter was in bad shape. I actually tested the battery a few days before and it looked fine. This time, however, when I got home I tested the battery again and the battery analyzer showed that the battery was weak/needed a charge. I charged it overnight, and the battery was reading fine again. The gentlemen who helped with the jump start said that a lot of times there's enough power in the battery to run the starter, but not enough power to ignite the spark plugs. He had seen it a lot.

I'm going to check for a parasitic draw just in case since the alternator appeared to be working fine and the battery is only a year and a half old. I saw a good how-to on checking for parasitic draws on Eric the Car Guy's Youtube site. There also may be a contact problem somewhere along the electrical path. It may take a while, but this type of thing is fun for me since I can learn more about this A4 and autos in general as I eventually figure out what the problem is.

I'll probably post a new thread since this doesn't look like a coolant temperature sensor issue anymore.

Thanks again guys.
Pete
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Old 04-09-2012, 10:57 AM
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One additional fail-prone part is the ignition switch. Mine was internally shorted and causing a drain as well. New switch fixed it. It's inexpensive ($25ish) and easy to install if you're comfortable messing with your airbag.
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  #8  
Old 04-10-2012, 12:44 PM
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Pete!
I had the same symptoms in my car exact same!
And it ended up being the cts! I under stand you don't want to throw parts at your car but for the price of the temp sensor if wouldn't hurt.( i paid 9-12 bucks for it ) I got mine from my local vw dealer much cheaper than Audi for the same part!

Imthedevil could be right to. Take a meter to your battery while in the car and check it every hour or so to see if there's a drain.

And when you do start your car watch the battery gauge with the ignition on sould be around 12 when starting shouldn't drop below 9

Just my thoughts
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Old 04-10-2012, 12:49 PM
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And how the heck did you put up with that for a year!!?
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Old 04-10-2012, 07:08 PM
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Thumbs up Thanks!

Thanks guys. I'll have a chance this weekend to continue the investigation. My multimeter just went on the fritz, and I won't have time to get a new one for a few days.

Actually, my wife asked me the same question - why do I put up with it? Since I don't drive this car that often, it didn't really bother me. Usually I drive it for a short trip, it sits for more than an hour, and then I drive back home, so it never turned into a big issue. We've got a minivan that we use most of the time. The main reason I put up with it is that I love working on this car! It's almost like therapy whenever something needs to be fixed, and I just bide my time until I have a chance to get to it!

I'll keep you posted. Thanks again!!!

Pete
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Old 04-12-2012, 01:13 PM
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Question 75 milli-amp draw

I had a chance to get a multimeter, and it looks like there is about a 75 milliAmp draw on the battery. I think that is a little high or right on the borderline of being normal, from what I've read. It was too cold and dark for me to pull fuses to find out which circuit is causing the draw, but I'll try to get at it this weekend. Hopefully, it's one of the inexpensive parts that you mentioned...

Pete
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  #12  
Old 04-22-2012, 11:40 AM
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Question Update

I had a little time to work on this and found a couple interesting things. First, it looks like there is minimal to no parasitic draw when the car is off. Also, I am able to recreate the no-start just by driving a few blocks and then shutting down. When I run VAG-COM during the no-start condition, there is at least one fault code - Power Supply Terminal 30: Voltage too Low / P1602 - 35-10 - - - Intermittent. When I check the battery, it's at about 12 volts. When I disconnect the battery, it slowly works its way back up to 12.5 - 12.6. When I re-connect, it drops back down to about 12. So it looks like something is drawing about .5 volts when the no-start happens. I didn't check amperage.

After I jump start it, the battery goes back to normal and the voltage draw disappears too. I'm not sure what's causing the draw, but I'll have a chance to look at this again and try pulling fuses in another few days.

Also, I checked the temperatures sensor readouts again in VAG-COM, and Audiltr may be right because the sensors showed that temp was around -60C to -180C and kept jumping around all over the place. There are 2 temp readings and they were both really low and bouncing around. I'm not certain which is the CTS and which is the MAF, etc., but either way I think the readings are wrong. I'll probably change the CTS since it looks like it's faulty and Audiltr says his symptoms were exactly how I previously described.

I'll update again if and when I get closer to figuring this out...

Pete
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Old 04-22-2012, 11:53 AM
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Interesting - the low voltage at terminal 30 indicates a low voltage at one of the output pins of your ignition switch. It can happen for many reasons. The ignition switches in this generation of Audis are notorious for screwy failures and internal shorting. It might be worthwhile to just replace it. They're $25 from FCP Groton and pretty easy to change out.
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Old 04-22-2012, 05:25 PM
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Thumbs up Ignition Switch

I'll give it a shot! Thanks!
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Old 04-23-2012, 11:43 AM
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ECS Tuning has an "Genuine" OEM ignition switch for $25 as well
Audi B5 A4 Quattro 1.8T > Interior > Switches > ES#1896875 Ignition Switch - 4B0905849

I'm thinking about getting this, cheap enough that in my mind I think "why not".
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  #16  
Old 04-24-2012, 07:36 PM
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Smile CTS Replaced

I received the new CTS today and switched out the old one. Surprisingly, it took less than 5 minutes. The old one looked a little cruddy - I'm attaching a photo. There was also some white gunk floating in the CTS chamber. I cleaned it all out before inserting the new sensor. I'm not sure if either of these had anything to do with the no-start.

I went on a couple of test rides, and things appear fine. The temperatures still look a little screwy though, and it may take a while before the no-start occurs again. I'm still going to change the ignition switch just in case since it's pretty cheap and doesn't look too hard to do. I actually found one on Ebay for about $8 including shipping, so I might as well give it a shot. Either way, I'll post another update once complete.

Thanks again all!

Pete
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  #17  
Old 04-26-2012, 04:25 PM
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Any body have any ideas what else could cause this problem? I recently replaces my ICM for a cyl 3 mis-fire, the ICM fixed that problem but Now I'm having the same crancking but no start issue. Driving me nuts. I don't see how anybody stands it not to mention, its embarrassing...car cranking for 30 seconds or so. I read down some other post in this forum so I just replaced the coolant sensor and still having the same problem
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  #18  
Old 04-28-2012, 06:17 PM
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Thumbs up Ignition Switch Complete

Another update - I changed the ignition switch, and everything is still fine. I'll post if the problem comes back, but I'm hoping that these two fixes did the trick. Also, I made a write-up of the ignition switch replacement because I couldn't find one that matched my vehicle 100%. However, it's over 1Meg with the photos, and I can't post it here. Does anyone have any suggestions?

Thanks again!
Pete
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  #19  
Old 04-29-2012, 12:13 PM
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Thumbs down Bad news.

The no-start returned. At least we ruled out the CTS and ignition switch. I'll keep working on it. There is something definitely pulling some power out of the battery when the no-start occurs, so I'll continue where I left off and pull fuses/disconnect wires until I find out what is causing the draw.

I'll start a new thread since we know it's not the CTS now...

Thanks again everyone!

Pete
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  #20  
Old 05-03-2012, 04:13 PM
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Thumbs up Fixed

I had a chance to pull wires, etc. and it looks like the alternator/voltage regulator could have been the culprit somehow. I removed it, cleaned contacts and the housing itself, re-installed it, and everything is running fine. Even the CTS readings have stabilized. I don't know how or why. But I'm glad I don't have to spend any more time on this, for now...
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18t, 99, a4, aeb, audi, b5, coolant, cps, crank, cts, gauge, location, sensor, start, temperature


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