XC70 rough idle and poor throttle control Topic is solved

bradm612 · Post by **bradm612** » 12 Jul 2025, 12:26

Have a new to me 2006 XC70 that is giving me problems. Started with a burst coolant line that is mated to the PCV system. I removed the intake manifold and replaced that line along with the entire PCV system (bought the kit from FCP Euro) and any vacuum lines that were under there. I also cleaned the throttle body while I was at it, wasn't too dirty but figured why not. Now that it's back together it idles rough and when pressing the pedal it doesn't respond at first then jumps to 2k rpm. If I hold it around there the rpms jump up and down. I pulled the throttle body back off and checked operation with key on, engine off. It operates smoothly and in sync with pressing the pedal. I checked vacuum lines and electrical connections but can't find anything wrong. It is throwing some codes, P2112 and 0507. That's pointing me towards the throttle body but I don't understand why cleaning it would cause any issues. I've seen older volvos require reprogramming of the TB but these Bosch units are different and shouldn't need that. I've also seen some people say they still require an adaptation to be run in VIDA which I don't have access to without taking it somewhere. I also see people saying you don't need to do anything to these TB units, just throw em in and go. I've tried leaving the key in on position and letting the TB do its little start up calibration, tried driving around a bit to see if it'd relearn but so far no good. Any help would be appreciated I'm at a loss here and my wife is without a car to drive until I fix this.

Post by **jonesg** » 12 Jul 2025, 23:56

Did you unplug the throttle body from its harness?
Its a known problem , the contacts can become damaged when disturbed.
Some dealerships pigtail a new connector on to prevent comebacks.

bradm612 · Post by **bradm612** » 13 Jul 2025, 07:20

jonesg wrote: ↑12 Jul 2025, 23:56 Did you unplug the throttle body from its harness?
Its a known problem , the contacts can become damaged when disturbed.
Some dealerships pigtail a new connector on to prevent comebacks.

I did unplug it when I removed the intake manifold. I would think that if there were an issue with that plug that it wouldn't function smoothly or at all when I press the pedal with key in the II position?

Post by **chrism** » 13 Jul 2025, 09:41

While testing you may have bent the harness around in a way that it temporarily made full contact. You might even try the test again with an assistant operating the pedal while you bend the harness every which way - maybe not TOO violently.

bradm612 · Post by **bradm612** » 13 Jul 2025, 10:41

chrism wrote: ↑13 Jul 2025, 09:41 While testing you may have bent the harness around in a way that it temporarily made full contact. You might even try the test again with an assistant operating the pedal while you bend the harness every which way - maybe not TOO violently.

Good idea. I will try that today. Do you know if these throttle bodies require any kind of relearning via the VIDA software?

bradm612 · Post by **bradm612** » 13 Jul 2025, 12:19

Tested it again. With key on you can hear the hear the throttle body go through some sort of start up sequence. Moved the wire all around and nothing changed this. Had my wife press the pedal as I listened to the throttle body while moving the cable around. Still no change, sounds like it operates perfectly when the engine is off, but as soon as the engine is running it seems to act up.

Post by **chrism** » 13 Jul 2025, 13:15

I (needlessly) replaced the Bosch throttle body in the 2005 S80 2.5T that we used to own. It was absolutely plug-n-play.
In our case the problem boiled down to the ECM connection. Once it was removed and re-seated the car ran fine.

bradm612 · Post by **bradm612** » 13 Jul 2025, 13:18

chrism wrote: ↑13 Jul 2025, 13:15 I (needlessly) replaced the Bosch throttle body in the 2005 S80 2.5T that we used to own. It was absolutely plug-n-play.
In our case the problem boiled down to the ECM connection. Once it was removed and re-seated the car ran fine.

Interesting. Yeah I'd hate to replace a $250 part if it's not the issue. From what I've seen these Bosch units don't really go out. I'm thinking it's gotta be something stupid. I wonder if VIDA would allow more insight to tell if it's the wiring and not the throttle body. I think I'm gonna have to bite the bullet and take it somewhere

bradm612 · Post by **bradm612** » 13 Jul 2025, 13:22

chrism wrote: ↑13 Jul 2025, 13:15 I (needlessly) replaced the Bosch throttle body in the 2005 S80 2.5T that we used to own. It was absolutely plug-n-play.
In our case the problem boiled down to the ECM connection. Once it was removed and re-seated the car ran fine.

What were your symptoms that led to you replacing the throttle body? Similar to what I'm seeing? Or did the throttle body not respond at all

Post by **jonesg** » 13 Jul 2025, 15:30

the code is indicating the ecm isn't recieving throttle information.
I wonder if a throttle sweep test can be performed in vida whilst the engine is running.

You could try a drag test on the throttle plug contacts, or just cut it off and install a new plug.
Its a lot cheaper than a new thottle body.