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Discussion Starter #1
2012 Giulietta Multiair 170hp.

I keep going into limp mode, especially at low speed/low revs. P1120 error code, which points to Throttle Position Sensor problem. Where is the sensor located? My car is right had drive.
 

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Throttle position sensor, not gear lever position sensor.

Throttle position sensor will be on the throttle body. Accelerator position sensor near the pedal.

It will look like a black box, square or round possibly with two screws holding it in place. An electrical plug attached. More than likely will need calibration after fitting.

In this diagram the whole inlet manifold is shown, 10255, the throttle body is on the right hand end.
https://alfa-romeo.7zap.com/en/giu/x7/191b53001000-099/102/47+10247-030+0-0/


Here is a previous thread, there's a photo of the throttle body. The tps will be under the large black cover.

https://www.alfaowner.com/Forum/alfa-giulietta/1147009-fail-code-p1120-giulietta-1-4-multiair-170bhp-year-2011-a.html
 

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Discussion Starter #4
Throttle position sensor, not gear lever position sensor.

Throttle position sensor will be on the throttle body. Accelerator position sensor near the pedal.

It will look like a black box, square or round possibly with two screws holding it in place. An electrical plug attached. More than likely will need calibration after fitting.

In this diagram the whole inlet manifold is shown, 10255, the throttle body is on the right hand end.
https://alfa-romeo.7zap.com/en/giu/x7/191b53001000-099/102/47+10247-030+0-0/


Here is a previous thread, there's a photo of the throttle body. The tps will be under the large black cover.

https://www.alfaowner.com/Forum/alfa-giulietta/1147009-fail-code-p1120-giulietta-1-4-multiair-170bhp-year-2011-a.html
This is a great help, can it be cleaned or will it need to be replaced?
 

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Quite probably the only cleaning possible is that of the external connectors. Basically inside the tps there is a potentiometer and one possible cause for failure could be the 'wiping' brush and 'track' have worn. Then again it could be more advanced. All very tentative but that's all I've got on that! I have seen programmes where the tips has been overhauled and modernised such as on Maseratis. Have a look online for the tips you could be lucky and I might not be that expensive, hopefully.

I've been looking online, as jomper says it is the whole unit. There are pre-owned bodies on eBay at reasonable prices but you'll need the part number from the side of the throttle body and will be a gamble. Wide range of prices for new from £120 to much more, and again non Bosch could be a gamble. Try what jomper says before shelling out.
 

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You have to replace it as a unit (and they are not cheap...), so make sure you try diagnosing the fault as much as possible before throwing parts on it. MitoNo3 posts a diagnostic chart in the thread armoore linked to. Replacing the TB is no 5 to do on that list, so start with checking the connector and if dirty etc clean it with electronics cleaner. Always disconnect battery first.

The throttle body itself can be DIYed, but is a very tight fit of a job (unless you remove more tubing to get more room). Takes a while to do mainly due to the cramped conditions and "blind" insertion of bolts.

Edit: I guess you could also try running the relearn diagnostic procedure in AlfaOBD or MultiECUScan and see it helps.
 

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Discussion Starter #7
Just to add some context, the car is tuned and has a mild map on. My tuner loaded a new map in which he set the TB to open 100%, instead of 82% or something. It ran well and I only got the error once and for the first time. He surmised the TB doesn't like the SW and we loaded the previous map, but the problem pops up regularly now.
 

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In that case there could be corrupted files within the original map now or parts of the new map haven't been deleted completely and there is a conflict. The sensor is just that, a sensor to determine the position of the butterfly valve. It could be sending the correct signal (voltage) but the map isn't recognising it as valid. Therefore throws it up as being faulty.
 

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Discussion Starter #9
UPDATE: I bought the full version of the AlfaOBD app, and reset the throttle position and learned values on the car. So far the error hasn't come back and the car has been driving smoothly.
 

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Discussion Starter #12
The joy is short lived. The error came back again. I cleared it again, and the car feels fine. I'll load the stock map this week and see if it still messes around.

The app costs about $15
 

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Discussion Starter #13
After driving around with this intermittent error, I took it off and cleaned it. It didn't work, and made the problem worse.

So I took the TB from a 156 2.0 TS, and simply swapped the circuit board (the black plastic cover) over. It's the same thing. Works fine now.
 
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