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HELP! replaced fuel tank vent valve, now have 4 throttle position codes

5K views 33 replies 10 participants last post by  thekurgan 
#1 ·
Replaced the fuel tank vent valve today because I was getting the recurring CEL for it. Pulled the intake plenum, installed the new part (genuine BMW), then put everything back together, double checking that every bolt and nut was snugged down properly with 10nm on the lower plenum and about hand tight on the horns.

On the road after the install, once it got up to operating temp, I floored it in 6th at about 65mph to see if the new vent valve added any pep. Slowly accelerated to 80mph, then all of the sudden went into Engine Failsafe Mode and cut power and RPMs limited to about 2000. Limped it off the freeway and down the feeder a bit to a parking lot.

Pulled the following codes:
P1637 - Throttle valve position control, control deviation
Stored codes:
P0221 - Throttle/pedal position, Sensor/Switch B Circuit, Range/Performance
P0121 - Throttle/pedal position, Sensor/Switch A Circuit, Range/Performance
P1639 - Throttle valve position control, Throttle stuck permanently

I cleared them, then fired the car up, still sounded like it was running on 4 cylinders and the following two codes immediately came back up as well as Engine Failsafe Mode - P1639 and P1637.

I didn't touch the throttle or linkages. I gave them all a quick squirt of carb cleaner but never manually operated the blades or linkages. I did move a vacuum hose, could it be rubbing the throttle linkage and throwing all of these codes?

Thanks for any help, need to get back on the road
 
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#3 · (Edited)
Thanks for the idea! I'm usually pretty anal about my tools, they all have a place so I probably would have noticed BUT fingers crossed its a tool or other obstruction in the linkage.

If it isn't evident what the problem is when I get in there, how can I rule things out, like the throttle actuators, TPS being bad, bad signal from the pedal, etc?
 
#5 ·
Hey TX Tahoe, you and I bought our cars at about the same time and I am also having similar issues with throttle position, although mine does seem like it's a bad throttle sensor.

Any way, would be good to get together once we have our cars road worthy. Maybe we could do an all call for cars and coffee for beasts in the Houston area. I live in Missouri city.
 
#6 ·
Sounds good, I'm planning on going to the one at Cedar Creek on June 11.

I'll post up once I tear into it and hopefully resolve my issue(s)
 
#8 ·
9-12pm on June 11th at Cedar Creek in the Heights. Mix of old (80s and 90s) and new, very friendly crowd. Going to try to make it, but got a baby at home so nothing is guaranteed. PM me if you plan on going.
 
#9 · (Edited)
So pulled the plenum off yesterday and found one of blue shop paper towels I had plugged into one of the maf tubes to keep debris out stuck in one of the throttle bodies. I know, I'm an idiot. Pulled the lower plenum and popped the arm off of the throttle actuator, opened the throttle and pulled the paper towel out. Fired it up, sounded good, drove it about 100ft and parked it. All good, or so I thought.

Went to drive it later that day and didn't get 200 yards before I get the engine failsafe again. Pending code P0121, throttle/pedal position, sensor/ switch Circuit A, range/performance.

I'll admit I didn't turn the key two clicks forward and have someone work the throttle pedal to validate the throttles opened and closed properly before buttoning it up. I didn't have an extra person for it, but in hindsight, should have asked a stranger.

What could the P0121 be? It's only Circuit A, not Circuit B. Does that help narrow it down? Did I not snap the throttle linkage back together well enough?
 
#12 ·
I've read about them and the Carly iphone scanner. Do they provide additional or more detailed information than just the handheld scanner? My scanner will pull manufacturer specific codes, which is what a few of the initial codes were. I'm all for having the right tools and don't have a problem spending the money, but I want to make sure it's an upgrade first.

Circuit A is the primary read, when a failure in A is suspect the DME switches and uses B. But you are not getting the crosscheck code so I would try somethings first.
What I would do is disconnect the battery and see if you can get it to reset. It is possible the TPS got damaged but I doubt it. Something is likely out of sync. Truth is we are still in the dark on how to reset throttle adaptions but we know they exist. If the battery does not work then just keep driving the car around the block and resetting the key each time failsafe intrudes. It will re-adapt and likely that is what the problem is now, bad adaption. You may have to replace the TPS which means pulling the plenum again. To move the throttles you don't need to disconnect the actuator arm.
Ok, thanks for the explanation, I will try disconnecting the battery for a bit then reconnecting as well as clearing the codes. It sounds like the car is punishing me for not taking better care of it... which is warranted.
 
#11 ·
Circuit A is the primary read, when a failure in A is suspect the DME switches and uses B. But you are not getting the crosscheck code so I would try somethings first.
What I would do is disconnect the battery and see if you can get it to reset. It is possible the TPS got damaged but I doubt it. Something is likely out of sync. Truth is we are still in the dark on how to reset throttle adaptions but we know they exist. If the battery does not work then just keep driving the car around the block and resetting the key each time failsafe intrudes. It will re-adapt and likely that is what the problem is now, bad adaption. You may have to replace the TPS which means pulling the plenum again. To move the throttles you don't need to disconnect the actuator arm.
 
#13 ·
On my E90 the throttle reset procedure is to turn ignition on, engine off. Push the gas pedal to the floor and hold it for 30 sec.
Some say they hear sounds as things are being reset.

Not sure if this applies to the E39 but easy enough to try it. Supposedly all drive by wire bimmers have an adaptation program.
 
#15 · (Edited)
No dice. Tried two clicks forward and holding the throttle to the floor for 30 seconds. Tried clearing the codes five times then driving it, and finally disconnected the battery for an hour, but within 100 yards, or when revving it sitting still, the car goes into engine failsafe and P0121 circuit A is in pending codes. Sometimes it feels like the engine is misfiring above 3,000 rpm when slowly revving it while sitting still.

Do I have a deeper issue? Had zero of these symptoms before this repair. Is the misfire tied to the throttle problem? Am I just being impatient and need to keep resetting the code and driving it?

If I pull the plenum again to see how the throttles are reacting at two clicks forward, will that get me anywhere in identifying the problem? Do I need to bite the bullet and take it to the stealership for a proper diagnosis or throttle relearn?
 
#27 ·
This makes sense since tbs don't open until around 2500 rpm. I assume one or both sides are not opening so you're going rich and misfiring. Do you have INPA? You could look at fuel trims specifically STFT to see if it's both banks or just one that is affected.
 
#16 ·
Just my bad experiences with TPS, replace it. Not an easy job, but not hard. Get the right bit though it is not a standard PH2 or north america #2 phillips. It is a euro #2 which here we call a #2 reduced, it is the same as a drywall screw bit. If you use a PH 2 you will strip it. The angle of the tip is wrong.
Don't know why this works but replacing the TPS will reset the system, and I would bet big bucks if after you replaced it then put the old back in the car would still be fine. Don't waste your time though, but save it in case you run into this problem again.

I am guessing it only resets when it notices a change in the electrical makeup IE new part. It is the only way I know to reset the system. Even in the programs (DIS INPA) I can find no way to reset the system.
 
#17 ·
Thanks. I guess I'll replace both while I'm back there, I believe they're original.

Is the misfiring tied to the throttle issue? It revs fine to 3,000 in neutral, then starts missing past that, even before engine failsafe.
 
#18 ·
Tx, for starters have the hood open , turn the key to position two and hang out under the hood you should hear the throttle motor do a self test or relearn in two min of the key being on. If not have someone turn the key off and listen for the throttle bodies there will be like a double clack noise. As far as your misfires go im thinking you cracked the plastic elbow that feeds vacuum to the purge valve.

If you do not hear the above maybe someone in your area has a gt1 you can see values and run an edk test.

I would start from basics and take the plenum off and check all your connections, keep in mind the car will run with the upper plenum removed so leave it off till you find our issue Im sure its something basic and over looked since the car was fine before purge valve replacement
 
#19 ·
Agree, it had to be something that happened during EVAP valve replacement, that is a job from hell. Did you try disconnecting and reconnecting your TPS connectors yet? Perhaps you stretched the harness to the TPS. You might try backprobing the TPS with car running and giving it some throttle, see if one side is showing weird voltages.
 
#20 · (Edited)
Based on your description, it does not sound like there are any installation errors, bad connections, etc... The fact that the car was driving around just fine until the rag got sucked into the throttle body area; whereas now the car does not drive fine without throwing throttle body related codes clearly shows that your problem lies with whatever effect that rag had on your throttle bodies or TB actuator. It may be very possible that the actuator has been damaged from the butterflies jamming against an obstruction.

Step 1: Pull the plenum upper and trumpets. Check for proper operation of the throttle bodies. Make sure nothing got bent or broken from your shop rag getting crammed in there and fighting the throttle motor. Check for more rags! :)

*Note: With the lower plenum off, you can actuate the throttle bodies manually by turning the linkage on the actuator by hand....no need to remove linkage. Also a good time to check connectors and plastic elbows and such.

* I see no reason why you cant run the engine with the entire plenum removed....I wouldn't recommend driving it this way, but if you can duplicate the fault with a couple quick stabs of the throttle in the garage....go for it. Make sure no rags are nearby. :)
 
#21 · (Edited)
Previous post has some good advise in it.
I ran into a similar problem and others with ESS kit did as well.
Let me ask you this, when replacing the vent valve, did you mess with the fuel rails/injectors at all? did you remove them to make room for your valve replacement?

If you did, I'd remove the intake manifold completely and manually actuate the throttle linkage and make sure the throttle body flaps open completely to 100%. More than likely you have an object obstructing the throttle linkage from opening all the way.

In my case, I had to cut the washers on the bolts that hold down the fuel rails to make room for the throttle linkage.

Good luck!
 
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#22 ·
Huge thanks guys! I'm going to start by pulling the cover and horns, then turning the key to 2 to listen for the actuators, then will start her up and have my wife modulate the gas to see if the throttles are moving smoothly and in parallel. I'll then pull the lower plenum to check for interference or anything loose. I'll also try disconnecting and reconnecting the TPS units. Do I need to turn the key to 2 in between so the computer notices they are disconnected?

If that doesn't work, I'll find a local shop with a gt1 or scanner that can log values. My scanner didn't have a value for tp% when looking at real time data.

I didn't touch the injectors or fuel rail, but I'll check clearance while I'm in there.
 
#23 ·
You won't likely see the throttles move if it is running. If it is running the ICV will control the air completely until a certain power level that you can't reach sitting still. If you leave the key in 2 and don't start the car you will see the throttle plates move.
 
#24 ·
Ok thanks. Will unplugging one or both of the TPS prompt a throttle relearn?

If the throttle plates don't move with the key in 2 (they didn't when the paper towel was stuck in there, hence why I had to disconnect the linkage), what does that tell me? Likely bad throttle actuator?
 
#26 ·
If they do not move in pos 2, maybe try removing the butterfly linkages from the actuator to isolate stuck butterfly/linkage vs bad actuator.

There is currently a used actuator in the FS forum BTW.
 
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#28 ·
So if my throttles aren't moving, which it sounds like is the case, could that be caused by a bad throttle adaptation? Don't want to start throwing parts at it if it's a software problem. Unless of course that's the only way to fix a software problem.
 
#29 ·
I doubt it...regardless, why would you suddenly have a bad throttle adaptation?
 
#30 ·
See what is going on. Get it apart. After re reading and looking up your code in AllData you may still have something interfering with bank one. You may still be missing a tool, towel or moved a hose, wire where you should not have.
I read through the causes for that code and the cause is when the position reached is not as suspected. That sounds like something interfering. The actuator has it's own codes and would throw one if it finds fault.
 
#31 ·
I would have taken the intake manifold apart a long time ago and manually actuate the throttle bodies...yes manually with your hands...chances are you did something when you replaced the fuel vent valve or even you may have left something unplugged under the plenum....


Sent from my SAMSUNG-SM-G935A using Tapatalk
 
#32 · (Edited)
I hear you, but I have a wife and 4 month old so wrenching is limited to the weekend, family first during the week.
 
#33 ·
Good news, issue has been resolved. Another case of user error. The throttle arm that I popped off to open the throttle and remove the paper towel had popped off. I was too ginger when popping it back on and it clearly didn't seat. With the key at 2, my wife modulated the gas and the throttles opened and closed as expected.

This has been quite the adventure that could have easily been avoided. Thanks for all of the help and apologies for being an idiot.

I did notice that I have a bunch of carbon buildup on the back side of the throttle plates, but no trace of oil in the oil separator or plenum. What do you do to clean this, if anything?
 

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#34 ·
I noticed a buildup on the back side of the throttle plates as well. It could be cleaned with throttle body cleaner, but there isn't much point. I only cleaned the edges of the plate and the throttle body itself.
 
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