TomCat39

I started my car up yesterday and the car threw a CEL and started idling funny from cold start. Pulled the code and got the P2101. Looked it up and learned that it's title of this thread (Electronic Throttle Control System Malfunction).

Is there anything else that can cause this code other than a problematic throttle body?

I would like to be aware of all the ways this code can come about instead of just assuming it's the throttle body.

This is on a relatively stock K20Z3.

TomCat39

Bump....

I cleared the code and it hasn't come back yet and I am on the 3rd revision from the Steve from e-tunez. Not sure if tuning can cause the code, Steve is highly experienced and I doubt it is a product of his tuning.

I suspect the gears in the throttle body are worn and the code will return at some point. Ten years isn't that long but so goes drive by wire.

Still wanting to know if there is any other possible causes that can throw that code.

DCFIVER

Vehicle information would be nice......

TomCat39

Sorry, I figured stating that it was a stock K20Z3 would be indicative.

2007 Civic Si Coupe with common bolt on mods, S2 70mm full exhaust, cat delete and Injen Cold Air Intake.

Stock ECU is being tuned w/ Flashpro.

I also assumed the systems would be pretty similar for drive by wire and the P2101 malfunction code.

My research has come up with worn teeth on the actuator gear(s) and also broken tabs on the stepper motor. Either way, this is still strictly in the throttle body and I have not seen anything else that can account for the code.

DCFIVER

Guy ,I stopped trying to remember which engine came in what car in the B18c5, H22a4 days. There are simply too many variations out now.
Naw, while the P code itself might be universal,the code set criteria will vary between make and model.
Interesting. Ive never come across one with stripped gears..

The issue is almost always carbon build up on the blade. Many DIYers(and professional "mechanics" and "tuners") erroneously believe that you cannot clean an electronic throttle body. Not only can you clean them, you have to periodically.

Make sure the key is out of the ignition. Push on the plate and see if it moves freely(there should be some resistance). Liberally spray a rag with brake cleaner or if youre **** about details. throttle body cleaner, and wipe down the inside of the plate,top to bottom until it is shiny again. You can push the plate open as wide as you need to,as many times as you need to,you are not going to damage it.

I cant recall off hand the specific idle relearn, but a generic procedure is to cycle the key after you've cleaned it, then leave the key in the ON position for a few minutes, then start the car and let it idle for a few minutes.

The second most common issue with ETC is failure of the electronics in the throttle body itself. In that case you will need a new TB

TomCat39

Thank you!

I picked up another throttle body from a 2008 Si that I was going to clean up and slap on with a new gasket.

The teeth seemed to be other cars challenges. But Hondata tech stated on 8th gen site that the tabs on the motor break as being fairly common.

I did find how to clean it like you mentioned as well as it's in the FSM to do the same thing if the DTC doesn't return in the HDS when testing.

My thoughts is if it's sticking bad enough the plastic gear teeth won't handle the extra force being applied for long before breaking down. But I think you end up with a near permanent P2101 code.

The used part only cost me 150 bucks and has a 3 month warranty so I might as well slap it on after cleaning it up and then clean up mine for back up and maybe pop open the cover to be sure the gears are solid.

The FSM did mention avoid cleaning wiping the sides by the bearings to avoid removing the molybdenum coating there, that was the only precaution I saw besides make sure key is off to protect the fingers.

The idle relearn I found for this car is turn key to on for 2 seconds, start car and bring to 3000 rpm until fan kicks on, then drop to idle and let idle for 5 minutes. And do not count any time the fan is on against that 5 minutes.

Tuner has my fan low temp at 191 F so the fans stay on solid when idling once warm. And I think even if I adjust that, flash the ECU and then put it back for his tuning, each reflash undoes whatever idle learning the car has done....

Anyways, got the car to go work on and flash revision #4. Tuner mentioned a rich state in mid range power so that also might be part of some of the funk I heard this morning with the sticky throttle plate.

Thank you again for the added feedback. I feel much better about the situation unlike Saturday when the code popped up.

Cheers.

Edit Addendum: Cleaned up the used throttle body and noted only a very small amount of play when I pushed on the plate before the gears in the actuator could be heard turning, was rather difficult to get just the right pressure to find that play.

Cleaned my throttle body with it on the car and noted significantly more play and way easier to find the play in the plate before the gears could be noticed. The play isn't much but my TB with 355,000 Kilometers is a bit sloppier than the lower KM used on I picked up today.

Will definitely be throwing the lower KM TB on sometime this weekend. Just need to finish prepping it for the swap.

Also noted there is around a .5 mm gap top and bottom on the plate to TB body on these when fully closed. Definitely part of the idle air pass through design and why the carbon build up most likely messes them up. I believe the carbon tends to fully seal the plate to TB body and there is no air passing through after awhile forcing the ECU to crack the plate to get the necessary air.

DCFIVER

This is why you will almost never see a TB with stripped gears. The design is such ,that the ECU can forcibly shut the blade close if it detects a "run away" situation. The gears are pretty stout. Perhaps that gen Civic had a manufacturing issue with their TBs. That would explain Hondatas findings.

TomCat39

Well, the code returned yesterday. I shut the car off and restarted and the idle surge went away and the car drove okay to home with the CEL on. Pull the code, 1 active code only, P2101. Cleared the code and turned my car into the body shop.

So when I get the car back from Craftsman Collision, I will swap in the lower mileage throttle body with new gasket. I'm hoping the clears up the issue.

I did not see any issues with the harness plug into the throttle body. I will pull the negative from the battery and pull the ECU plugs for inspection.

I really am not sure what pins of the ECU go to the throttle body but I honestly do not expect to see any issues in the ECU plugs.

TomCat39

I forgot to provide an update so I will do this now.

I did not replace the throttle body even though I have one on hand.

Turns out the hole I had in the CAI was the culprit.
https://honda-tech.com/forums/honda-...atman-3310378/

I am suspecting the difference in air pressures was enough to throw a sensor or two out enough the ECU thought the throttle plate position sensor was inaccurate.

Ever since I patched the hole in the CAI and made sure it can't return, the code has never come back.

DCFIVER

Ehhhhhhhh, I dont think so.


The code set criteria isn't about pressure differential,its about position. or more correctly, and incorrect position. A hole in the pipe wont change the position of the throttle blade (which is being monitored by no less than 4 sensors)

Seems to be a coincidence to me,but Ive been in the biz long enough to not dismiss anything out of hand.


Engineering anomiles are alive and well with todays vehicles.....

TomCat39

I will keep that in mind as well as keep my backup throttle body.

It's just weird that the code and the hole in the CAI coincide. And the code has never returned after I patched the hole. Yet while the whole was there, I got the code 3 or 4 times, including once or twice after cleaning the throttle body without removal.

Thank you for the added info. Now I know it's even more important to have the spare throttle body as insurance.

Jeff S

FYI: I resolved the P2101 issue by simply cleaning (electrical contact cleaner) and reseating the throttle body electrical connector.

DCFIVER

Funny that this thread came up.

TomCat- You still here?

I wonder, did you experience any drivability issues, either when the code was set or before any lights came on?
Im specifically wondering if you had any hesitation during initial throttle tip in(light acceraltion from a stop) or tip in into 2nd gear.

Im the proud owner of a 9th gen, as of last year, and have been experiencing the above scenario lately. It has been so intermittent that Ive been unable to narrow my focus onto any particular system at this point.

Ryanthegreat1

I have a 9th gen Si and also notice hesitation and what I would call jerky throttle plate response. No codes, stock PCM.

Throttle body was cleaned up with some brake clean on a rag. Same issues even after many relearns and code clears.

Very noticeable on transitions either opening or closing. I find it very annoying. My two other TSX engines don't do this. One is completely stock and the other is running Hondata. Hondata made a HUGE improvement over stock for throttle feel. Nearing the point of going Hondata on the 9th gen Si just to fix the crap throttle feeling. And the part throttle rev hang is unbearable!

I have an Autel that will graph throttle plate request and throttle plate actual. With the two graphs overlaying each other they line up perfectly. No jitter or lagging. Maybe it is an emissions thing and the byproduct is a poor throttle feeling.

Jeff S

First symptom was the car went into limp mode and the check engine light came on. I shut the car off and waited a bit and turned it back on. I was able to drive home at regular speeds, no stumbling. Then I drove the car the next day and it stumbled when I came to a stop and went into limp mode again. It also stumbled right at initial throttle tip and shifting to second. The research I did brought me to this thread and some others, none of which seemed to have a solution. I spoke with some friends, one of which recommended cleaning the connector. That did the trick.