Ironcross

Hello all, I have a buddy who is having a ton of problems with his vehicle. I myself know more about American made cars. Which why I'm seeking help from you guys.

His vehicle popped this code:
-P1568 - Throttle Control Unit Mechanical Fault.

With a pending code:
-P1113 HO2S 1 Bank 1 Heater Resistance Too High.

So we pulled the throttle body off and cleaned it up and I had my father clean up the computer part of it. Plugged it up without bolting it to the car and turn it to the On position. Every time he turned the key it would open a few millimeters and close. So I had him start pumping the gas pedal and I had opened it by hand over 50% and it started working to what it was receiving from his actions. Then about 30 or so seconds it stopped working.

If you read this report: 2000 Audi A6 4.2L Quadttro.pdf

It is showing Engine Coolant Temp 419.00 °F for running for about 5 minutes. Before we took the throttle body off the computer was scanned.

Now one of my questions is where can I find the radiator cap or how to check the coolant on this vehicle?

As I have read if the car gets too hot it goes in to "limp" mode. Which could cause the throttle body to act up and pop that code?

Any ideas on where to start or what to replace?

I was thinking on replacing the temp sensor. I know there is two of them one for the coolant and the computer. Should I replace those first to see if this remedies the problem or if you guys can come up with a list. That would be much appreciated.

Thanks.

SloopJohnB@mac.com

OK...your first error was forcing the throttle body open by hand...it generally ruins the throttle body. If it won't open with the ignition on and someone stepping on the gas pedal it's probably toast.

The coolant temp sensor is near/behind the radiator on I believe the upper or lower radiator hose. You might be able to see it from underneath...I saw mine with the front bumper in service position and changed out its O-ring at that time..it was already the good green one and I was only concerned about leaks.

I think the P1113 HO2S code is for your oxygen sensor on bank one...I think that's the passenger side and probably the sensor in front of the cat. Could be a bad connection to the sensor or you might just need a new sensor.

There is no radiator cap per se...it's a big blue cap on the expansion tank near the firewall in front of the driver. BTW, the hoses for the radiator are held on with a wire bail/clip. You pull out the U-shaped clip and the plastic disconnects with some effort. Do not try to remove the hose itself.

Ironcross

What about the "Limp" mode that I've read before. If the computer sees it is running too hot can it cause the throttle body to act up? As it was reading 419 degrees F from idling for about 3-5 minutes.

As I said, when they key is turn from OFF to ON the TB opens a few millimeters and closes.

So it would be a safe bet and replace the throttle body? Just making sure as a new one can range from $500-1500.

Thanks.

MP4.2+6.0

Don't know about engine limp mode. Term is usually used for the tranny--locks into 4th gear only if tranny acts up, or related control systems (MAF, and maybe the throttle). But it does not prevent motor from operating at any given RPM by itself. If motor has a separate function like that for overheating and such, I expect it might regulate higher rev'ing, but not basic operation--should at least allow car to be driven to the side of the road or off the freeway or bridge in an emergency or its a lawsuit and recall waiting to happen.

Meanwhile, I would be looking for the usual faulty cooling sensor on the 4.2 back behind the cylinder heads. It is in the water lines pretty well buried back there; fastened with a retaining clip into a metal tube as I recall. If you are fooling with the throttle body, you likely have the big rubber intake elbow off. Remove that and the other parts of the intake air tubing system back to the MAF sensor tube and you should be able to find it down below. Single multiwire connector into a sensor sticking upward. Very common fail part on virtually every Audi once the car gets older, 4.2's included.

jseklund

Did you run the throttle body adaptation after you disconnected it? This may be a help.

Before I knew better, I had forced the butterfly open a few times on my mom's 2.7T throttle body and it still works fine today. I was lucky, and certainly don't recommend this - I dodged a bullet. Don't touch the door anymore.

If it were me, I would spend $15-20 and get a new green coolant temperature sensor. It is definately NOT your throttle body causing that code, and this part is cheap and a common repair item. Just do it. It may fix your throttle body issue, but I don't have high hopes.

SloopJohnB@mac.com

I'm not saying/accepting liability for replacing throttle body..there should be a way to check the TB activation using vag-com. If vag-com tells you TB is bad then you'll have to try replacing it with a known good one, either used or new. Personally, I'd get a used one. TBs generally last the life of the car...unless some ham handed noob forces the throttle plate open by hand....nothing personal!!!

How to clean a TB:

http://writen4u.hubpages.com/hub/How...ody-VWAudi-DIY

Ironcross

We'll give a go. We want to replace stuff that might fix it before having to spend big bucks. Thanks.


Will do, thanks.

Oh, I know its bad to open the butterfly by hand. But the little motor wasn't "on" then at 50% open it kicked in.

Yup, I cleaned it. Its smoother now. But has about ~15 pounds of resistance on the butterfly.

We'll see if the temp sensors are the problem and get back to you all in the next few days.

If there is anything any of yous can think of, I'd appreciate it.

Thanks.

4Driver4

[QUOTE=SloopJohnB@mac.com;24254428]OK...your first error was forcing the throttle body open by hand...it generally ruins the throttle body. If it won't open with the ignition on and someone stepping on the gas pedal it's probably toast.[QUOTE]

I agree that he probably destroyed the throttle body.

I do not, however, agree with the rest of your comments.

4Driver4

There are about three different people suggesting that you do a TBA. This a good advice. Once the TB has been unplugged from the harness, a TBA must be preformed before it will work properly.

Why are you ignoring this excellent advice?

Ironcross

No, I'm not ignoring advice. I had no idea on how to do a TBA on a Drive-by-wire till two days of searching on how to do it without VAG-COM.

What I had him do was disconnect the battery over night. Reconnected it, turned it to the ON position and let it sit there for 5 minuets or so. He just texted me that its working 100% and the code went away.

Now if I can figure out if the computer was screwy, bad sensor or there is low to no coolant in the radiator. How would I go about checking the coolant on it besides just looking in the reservoir. If its got coolant then I'm replacing the coolant sensor(s). Any tips?

Thanks.