E46 325 Throttle Valve Error?

[CypherP]

Hi all,

Im getting an intermitent fault on my E46 325ci. Last time i had it diagnosed at an indy, they got fault code P1632 (Throttle Valve Adaptation) but weren't able to tell exactly what is causing it.

Wondered if anyone had any ideas of areas to check or if anyone has had similar faults? I can be driving along and suddenly get engine check light and dsc light come on, but when stopping and turning ignition off and back on again, it seems to resolve the error as the lights disappear and it drives normally again.

Any help would be appreciated as considering the financial times, i could do without getting it re-diagnosed at the dealer and it costing alot more to fix? I havent been able to find much info, but a few people have mentioned it could be to do with the battery being old, or possibly the wiring?

[TheEnd]

There is 4 potentiometers in the throttle system. 2 at the pedal, where one runs roughly 0-2.5v, and the other runs 0-5v at positions from 0-100%

It keeps an eye on these, and makes sure one is always double the smaller one, so if one starts to fail, it'll be spotted quickly, and it'll use the more plausible signal as an emergency mode. At the throttle itself, there is a similar system, but 0-100% throttle gives signals from 0-5v on one potentiometer, and 5-0v on the other (reversed), ie at closed throttle, it'll have one 5v signal and a 0, at 50% they'll both read about 2.5v, and full throttle is one 0v and one 5v.

During the throttle adaptation, it'll measure all these signals very accurately and store the exact figures from the potentiometers. I'd imagine in this case, one potentiometer is giving poor signals, hence the error.

[CypherP]

Thanks for this. Thats probably the most detailed answer i've had on this since i started posting about it, so i appreciate it. I'll probably have another word with the indy and see if their answers relate to this.

[TheEnd]

It could possibly be the motor that moves the throttle binding/sticking, so when you say 50%, it tells the motor to move to the 50% position, but it reads 40% on the potentiometers, so it'll re-adapt to move the motor more to give 50% on the pots, only to find the next time, it's 10% over.
The code you have is a basic OBD2 one, so it's not as helpful as a BMW based code reader, but those are the main components, and how they operate together, and i'd imagine it's something to do with these that is playing up.

STOP PRESS!
OBD Codes with a 1 at the start at manufacturer specific.
The full name on P1632 on a BMW is "P1632 Throttle Valve Adaptation; Adaptation Condition Not Met "
http://www.aboutautomobile.com/DTC/P1632

That doesn't help too much, as i don't know what adaptation conditions are, but if a potentiometer is out of spec, or the motor can't move enough, then i'd guess the car can't record the adaptations.

[CypherP]

Makes sense, and having someone explain that certainly makes more sense than me trying to figure out which components might be playing up. It sounds more likely to be the latter, that the valve is sticking, as it only occurs once every couple of months, normally when the engine is reasonably cold. Once its warm, its not affected.

I think ill mention this to the indy and see whether they can free it up, or at least take a look at the throttle valve. I did try to clean the valve and a few other bits with carb cleaner, but the valve itself was inaccesible at the time as i didnt have the right tools to remove the necessary parts.

[TheEnd]

Be careful with carb cleaner. It's amazing stuff, usually a mix of xylene and methanol (which is a handy octane booster) and it's a very good paint stripper too, but it can soften plastics, and make the top layer swell.

Maybe it is only certain types, or it needs quite a while sitting in it to do so damage, but bear that in mind. There isn't any specific warnings on the cans, so possibly all the plastics used in intakes are OK, but try spraying some on a polystyrene coffee cup, and it'll dissolve before your eyes!

If you can get someone with BMW based diagnostics, you'll probably get a better idea, Carsoft usually copied the help info from BMW, and it can have more details on the exact cause and often tips on what needs to be done (although BMW's main fix is usually replace that component and anything within a foot of it!)

[CypherP]

Thanks, i'll bear that in mind, thankfully i haven't used any of it yet, only attempted to strip down the neighbouring parts before realising i didnt have the right tools to remove the rest of them at the time, but i'll probably get someone to have another look before attempting to do that again.

Forgive me for sounding a little niave, but what is Carsoft? Is this separate software, or is this a diagnostic tool that i can access through an indy?

[TheEnd]

Carsoft is a BMW diagnostic system, very similar to BMW's own GT1 tester they the dealers had, but made by a different company. The kits are about 2-3 grand, but they've been copied and ebay is full of the leads, and download/share the software, so as a result, there are a lot of people about with this diagnostics for home / DIY use.

[CypherP]

TheEnd said:

Carsoft is a BMW diagnostic system, very similar to BMW's own GT1 tester they the dealers had, but made by a different company. The kits are about 2-3 grand, but they've been copied and ebay is full of the leads, and download/share the software, so as a result, there are a lot of people about with this diagnostics for home / DIY use.

Excellent, well ill see whether i can locate someone who has this, or possibly try and get hold of something that may give me better ideas. Failing that, based on the info youve given me, i may go back to the indy and mention a few points, and get them to check them out.