Cruise control sometimes not available after cold starts

[cheba]

I have a problem with my 6R WRC which occurs intermittently. I first noticed it about two months ago and thought it was a one-time glitch, but for the last two weeks I have been monitoring the issue.

The problem is that sometimes when I flick the switch on the blinker stalk to turn on cruise control, nothing happens. No cruise control light in the instrument cluster, no symbol in the MFA, nothing. Just as if the car wasn't equipped with cruise control. Whenever the problem occurs, turning of the ignition and restarting the engine is enough to make cruise control come alive, at least until the next cold start.

It doesn't happen every time. At first I thought it was related to colder weather (like -10°C one morning which caused a lot of warning lights and a fault code on the throttle position sensor), but it seems I can also get the cruise control issue when the weather is "warmer" (and by that I mean "just above freezing" this time of the year). Sometimes I get the issue and sometimes I don't, and I can't see a clear pattern.

It also seems that when I lose the cruise control, it is during the engine start. If I turn on ignition and flick the cruise control switch the first thing I do, cruise control will always be on. After I turn the key to start the engine, cruise control will either be OK, or it will be completely gone.

I don't have VCDS, though if needed I can visit a friend who has it. I don't know what to investigate though...

I thought this would be a good place to ask since I know there are people here who know a thing or two about electronics on these cars

[iichel]

you could have a look at fuse number 10, maybe you can see some corrosion or whatever. I don't expect you can see anything there, but you never know...
Otherwise, you could have a look with a VCDS, just to see if the engine or BCM are complaining about a cruise control issue.

Otherwise, it's likely a broken or corroded switch. Happens from time to time. But I can't reason a logical connection with the cold starts.

[cheba]

you could have a look at fuse number 10, maybe you can see some corrosion or whatever. I don't expect you can see anything there, but you never know...
Otherwise, you could have a look with a VCDS, just to see if the engine or BCM are complaining about a cruise control issue.

Otherwise, it's likely a broken or corroded switch. Happens from time to time. But I can't reason a logical connection with the cold starts.

Ok, so I should hook it up to VCDS and read BCM codes?

What I have done so far is to use Torque for Android with and an OBD dongle to read ECU codes. I can see that there is a code for the throttle position sensor from that cold morning 2 weeks back. I know cruise control won't work if there is an issue with the throttle position sensor. However on that cold day, the warning lights disappeared and everything went back to normal after a couple of restarts. The only thing still pointing to an issue is the error code for the position sensor. When I checked last week the code was still in the memory but there is no warning light and the car runs as normal so I don't think there is an issue anymore (although in Torque it is shown as "Current fault" for some reason, I don't know if the error code will clear itself eventually or not). I think it's strange if there was a problem serious enough to shut down cruise control, without triggering a warning light or message.

I've read that the switches tend to fail but I am almost 100% sure it is not the switch or a bad connection elsewhere (since CC will always turn on if I flick the switch before engine start, but not necessarily if I do it after engine start).

On another forum we discussed the possibility of it being a bad battery, which could have a connection to cold starts (voltage dips too low which causes some functions to be disabled). However I haven't had problems actually starting the engine, the battery check during the inspection service last August showed the battery was still good, and the indicator on top of the battery shows it's OK. This makes me think it is not the battery.

[cheba]

I really doubt If it could be due to a bad battery, but I'm also getting confused about the battery... I measured the resting voltage yesterday evening with ignition off and everything else off, and it was juust above 12.0V. Measured a while later and it showed 11.8V, and then I thought it was indeed a bad battery.

This morning it was colder, (-6°C) and I thought that now when I start the car it would become apparent if the battery was bad. However the car started just fine, and I didn't even get the issue with the cruise control. I really can't see a clear pattern to figure out what's going on here...

[ciclo]

Hmm...

Thus:
- Everything is fine if you set the CCS before starting.
- But it works intermittently (undefined) if you set the CCS after starting, and one or the two accelerator position sensors provide the fault when the CCS not works.

A difference between 1st action and the second one is that the motor moves/vibrates.... and what is attached to the engine and related with this is the throttle valve module.
Maybe you should check and clean (if necessary) the connector and terminals of throttle valve module.

[ciclo]

Cheba, I recommend you read this SSP: (and all those who have a minimun of interest )

http://www.volkspage.net/technik/ssp/ssp/SSP_210.pdf

On pages 15,19, it will warn you about what is happening.

[cheba]

Cheba, I recommend you read this SSP: (and all those who have a minimun of interest )

http://www.volkspage.net/technik/ssp/ssp/SSP_210.pdf

On pages 15,19, it will warn you about what is happening.

Thanks a lot ciclo, good piece of info!

At least something sounds familiar:

Page 21, left column (one faulty angle sensor). This was what happened to me two weeks ago on the coldest morning of the winter so far. After starting the engine, EPC light was on, check engine light was on, there was a "!" in the MFA, cruise control was gone, but it did respond to the throttle pedal as normal and I could drive the car. After driving it back home, then started and stopped the engine a couple of times (I was trying to trigger a throttle valve adaptation but I don't think I succeeded) the EPC and engine warning lights were gone.

But the strange thing is that while I still have the error code "P2101 - Powertrain: Throttle Actuator Control Motor Circuit Range/Performance" when I do a OBD scan, and sometimes the cruise control gives up, but I don't get the EPC and engine warning lights. Does this mean that there is still an active problem or not? Shouldn't the warning lights be on if that was the case?

I would think that the left column on page 21 is the situation I am still having, if it wasn't for the fact that I don't get the warning lights any more.

Also on page 22, it says that the EPC light should go out in 3 seconds after turning ignition on if all is OK. Is this info incorrect/outdated? (after all, the document is from 1999 ) After turning ignition on, my EPC light and engine light stay on until the engine is started. After checking out some Youtube vids showing gauge sweep on the Polo 6R, it seems that this is the normal behavior on the 6R.

(Actually I also recognize the right column on page 21. Happened two years ago on a cold morning while on a trip up to Finland. It was a real Finnish cold that morning The car didn't respond to the throttle but I could drive the car in first gear. But after stopping and restarting the engine, everything was perfectly normal)

[ciclo]

Ok, ok, nice stories... hehe (driving your WRC in first gear had to be exasperating or fun ... haha)... yes, yes, is an old SSP, but it helps us to communicate more clearly.

I suppose you've already checked this https://www.obd-codes.com/p2101

The fault should be cleared with the VCDS (for example) until it happens again.

Maybe it's time to do a little cleaning of the valve with one of those magic sprays and perform the basic adjustment of the valve with the VCDS.
The process is explained in the Ross-tech Wiki, it must be done meticulously, maybe it helps or maybe not but it does not hurt to do it.

[cheba]

Ok, ok, nice stories... hehe (driving your WRC in first gear had to be exasperating or fun ... haha)... yes, yes, is an old SSP, but it helps us to communicate more clearly.

I suppose you've already checked this https://www.obd-codes.com/p2101

The fault should be cleared with the VCDS (for example) until it happens again.

Maybe it's time to do a little cleaning of the valve with one of those magic sprays and perform the basic adjustment of the valve with the VCDS.
The process is explained in the Ross-tech Wiki, it must be done meticulously, maybe it helps or maybe not but it does not hurt to do it.

I checked the obd-codes.com link now, but the info is kind of generic...

It is tempting to try to clear the fault code using the OBD dongle and the Torque app, but is okay to do this unless I know the problem is solved? Or does clearing the fault code now make it harder for a professional to troubleshoot it, in case that would be needed?

I am thinking of asking someone with VCDS help me do a Throttle Body Alignment according to this: http://wiki.ross-tech.com/wiki/index.ph ... ment_(TBA). Probably it doesn't hurt to clean the valve, but removing the throttle body from the intake seems to be a real pain on the 2.0 TFSI, so I'd prefer to leave it unless I absolutely have to. At least for now, because of the weather and I don't have a garage space at the moment...

[ciclo]

For that reason I told you to start with the easiest and simplest thing, such as checking the connector of the valve. Honestly, I already thought about the possible conditions in which you could be (wheather, workplace/tools)

Well, to carry out the basic adjustment of the valve or to erase the faults, I recommend the VCDS. It is better not to risk.
I have done this process two or three times in my TSI (for research reasons ) and the process was carried out correctly.

As you can see I have overlooked the cold temperatures you mention and their influence on this problem. It should NOT affect, but the reality is that everything is so perfectly adjusted that a minimum variation in materials (due to extreme temperatures) can influence.

Bear in mind (only ) the possible purchase of a new valve, maybe it ends up being a totally reliable solution ...for the next winters.

[cheba]

I did a very quick check on the connector and made sure it was plugged in properly. I didn't try unplugging the connector to check the inside though (I hadn't disconnected the battery so maybe not the best idea to be unplugging sensors).

I guess I'll also try to get someone with VCDS help me do scan for all the codes, then clear them and do a throttle body adaptation, then see if the codes come back.

[cheba]

The last couple of days we have had colder weather again. It became quite apparent when starting the engine that the battery is quite weak. Also during this cold weather the cruise control has consistently been disabled after cold starts. Today I bought a new battery and installed it. The old battery was just under 12,0V when hooked up to the car, the new one is 12,6V which is what a healthy battery should be.

I did a scan for error codes with Torque before disconnecting the old battery, but nothing showed up. I tried it 3 times, turning off the ignition and unplugging the dongle in between. No codes. Perhaps I have driven the distance needed for the throttle actuator code to be erased from the memory.

[ciclo]

Hopefully the CCS will not be disconnected again with your new battery.

[cheba]

Hopefully the CCS will not be disconnected again with your new battery.

Unfortunately this was not the case. This morning the weather was even colder, so it was a perfect opportunity to put the new battery to the test. After the first start, CCS was gone, just as with the old battery.

I noticed during the start that even with a new battery there was quite a voltage dip when the starter kicks in, but since the battery is healthy, there should not be more of a voltage dip than the electronics system is able to handle without disabling comfort functions.

[ciclo]

Ok, so we continue with the research process to solve this problem.