P0638

[breacher]

Hello Folks, I've done some searches for P0638 and didn't come up with much. at least not for Diesels. the ones I've come across were Mimi Cooper S and E90 M3's that have seen this issue around 60K.
They said that P0638 is rare, it's a non wear item and that it should last the life of the car...

I have a 2011 X5 Diesel in the US. I just got the code today. Is this something to drive safely with? It's not in Limp mode or antyhing. I cleared the code with AutoEnginuity. Hasn't come back yet.
I didn't even think the Diesels had a tradition type Throttle-Body, etc?
Still learning. Thanks.
I've only test drove it for roughly 5 miles without the Check-Engine-Light coming back on. Wonder if it takes 100+ miles or what?

Thanks all.

[Ron07x5]

Originally Posted by breacher

Hello Folks, I've done some searches for P0638 and didn't come up with much. at least not for Diesels. the ones I've come across were Mimi Cooper S and E90 M3's that have seen this issue around 60K.
They said that P0638 is rare, it's a non wear item and that it should last the life of the car...

I have a 2011 X5 Diesel in the US. I just got the code today. Is this something to drive safely with? It's not in Limp mode or antyhing. I cleared the code with AutoEnginuity. Hasn't come back yet.
I didn't even think the Diesels had a tradition type Throttle-Body, etc?
Still learning. Thanks.
I've only test drove it for roughly 5 miles without the Check-Engine-Light coming back on. Wonder if it takes 100+ miles or what?

Thanks all.

Doing a google and reading a bit sounds like this is an error saying your fly by wire throttle control is out of the spec range. In isn't a throttle body error. I believe what is going is when you press the throttle say 25 percent the computer tells some actuator to move 25 percent but it moves significantly less or more than that according to a sensor and you then get the check engine p0638.

[Ron07x5]

I do know but since it isn't in limp mode I would think it safe to drive. However it might mean your throttle cable is failing and may totally fail.which could be big.problem if in heavy traffic.
If mechanically inclined you might inspect the throttle stuff under the hood to see if.you can see a.problem. might be cured with some lubricant but probably not.
The problem should continue and likely happen more and more ... you should have it fixed. Seems to me any independent bmw repair should be able to fix this easily provided they can easily find what.is wrong.

[Doug Huffman]

Originally Posted by Ron07x5

[ ... ] However it might mean your throttle cable is failing [ ... ]

Uh oh!

[ZetaTre]

Throttle cable?!?!?!

There's no throttle cable and the throttle the car has is not for the purpose of regulating engine load. There is a throttle butterfly but it's there to have a smooth shutdown of the motor; it is also used during the DPF regeneration.

It does get shorted by soot & oil getting into the circuitry. So perhaps that's what is going on.

Once it totally fails the code will stick and you'll notice the engine shuts off like an old diesel tractor.

Until then you're fine.

Take a look here at what happens to the throttle: P2621 Throttle position , output signal - circuit low - Bimmerfest - BMW Forums

[ninja_zx11]

This fault points that there is high temperature detected inside the DDE(diesel engine computer) in the circuit that controls the throttle valve.There are couple of things that can cause this issue.It could be your bad throttle valve that is putting strain on the DDE and its raising the temperature or bad wiring.Or E-box fan is not cooling the DDE properly.And it could be more serious issue with DDE itself according to the rheingold(bmw diagnostic software).
Screenshot attached.

[ZetaTre]

Very interesting stuff ninja!!!

Interesting how it says that's something blocking DPF regen -> add to the list of things the ECU checks before moving it from requested to active.

But back to the topic: you mention wiring and DDE fan but could this excessive temperature again be the result of dirt in the throttle circuitry similar to this



That results in a excessive current being absorbed the the throttle to maintain a certain position?

While bad wiring is possible (often rodents or clumsy mechanics), the DDE fan is monitored directly by the DDE so it would be odd that is not directly detected.

[ninja_zx11]

Originally Posted by ZetaTre

could this excessive temperature again be the result of dirt in the throttle circuitry similar to this



That results in a excessive current being absorbed the the throttle to maintain a certain position?

Quite possible ZetaTre as we already know that throttle valve gets filled with CCV and egr junk.

[Doug Huffman]

On an ALH TDI it is called, more descriptively, the anti-shudder valve. It's operation is checked as the only installed defence against a runaway engine fuelled by lube oil through failed turbo seals.

[ninja_zx11]

Originally Posted by Doug Huffman

On an ALH TDI it is called, more descriptively, the anti-shudder valve. It's operation is checked as the only installed defence against a runaway engine fuelled by lube oil through failed turbo seals.

Plus on ALH engine it helps to stop the engine smoothly and quickly (same use on our M57)by blocking the air but its operated by vacuum on ALH TDI.