Citroen C3 2006 Rough idle and SERV light on

[Moyhentaja]

Hello,

i have a citroen c3 2006 1.4i. The car has a problem with diganosis says Engine managment fault in radio diagnosis, dash says "SERV" and obd codes it gives out are P0122 & P2122. The car wont respond to thorttle and the idling is rough. Sometimes the problem goes away and sometimes the problem persists. So far i have dissassembled throttlebody and found no issues, throttle pedal (hall effect) found no issues with it whatsover. What could be the problem?

[mickthemaverick]

Have a read through these guides and you may get some ideas:

https://carscounsel.com/p0122-code/

https://www.troublescan.com/p2122/

[Moyhentaja]

Have a read through these guides and you may get some ideas:

https://carscounsel.com/p0122-code/

https://www.troublescan.com/p2122/

Nice one..! I have gone through these components and also cleaned the sliding surfaces of the throttle position sensor. There was no problem with these components and the resistance between the sliding surfaces was linear in the throttle position sensor. The fault occurs randomly and now most often making the car unusable. Sometimes the car may work for a while, sometimes the fault disappears after restarting the car 3-5 times. The car hs done only 95000km's! Car has new battery & alternator..

Does anyone have the circuit diagrams of the ECU and the throttle and pedal?

[mickthemaverick]

This is my best shot at your diagram. You will find a guide to reading it at:
viewtopic.php?p=782862#p782862

c3 ignition.pdf

Copied from Sedre backup

(2.74 MiB) Downloaded 19 times

[Moyhentaja]

This is my best shot at your diagram. You will find a guide to reading it at:
viewtopic.php?p=782862#p782862

c3 ignition.pdf

Very nice! These scematics are a handful to even read. I couldn't identify a gas pedal symbol or throttle body symbol.. Sad to admit I have a masters in electrical engineering and frenchman has outdone himself

[PaulC5]

We had a 2003 C3 1.4i petrol and I replaced the accelerator pedal as it was difficult setting off with the revs not going up gradually as it was pressed. I also vaguely recall there being a problem with some cars with the wiring between the pedal and throttle body. Some early cars might have had a recall on the pedal.

When you say you have checked components, have you actually replaced them with known good ones ?

[Moyhentaja]

We had a 2003 C3 1.4i petrol and I replaced the accelerator pedal as it was difficult setting off with the revs not going up gradually as it was pressed. I also vaguely recall there being a problem with some cars with the wiring between the pedal and throttle body. Some early cars might have had a recall on the pedal.

When you say you have checked components, have you actually replaced them with known good ones ?

No I have not replaced the components, I dissassembled the pedal and visually checked the electronics for any visible damage, as it is hall effect sensor I cannot see a way it could fail. As what comes to the throttlebody I did dissassemble the throttlebody and visually checked the components and measured the potentiometers (TPS) component for resistance in according to the position of the throttle shaft, everything seeemd linear and as should. Also cleaned the TPS carbon rails of the potentiometer. As being said the problem occurs completely randomly.

I just checked Ignition on, engine off the throttlebody TPM says its 9,8% open and when pedal is pressed the TPM reports 82,4%, read from OBD port. Could this be some kind of calibration issue? Should it be reading 0% and 100% ?

[mickthemaverick]

You may get an idea from this video too if you can put up with the narration!!

[Moyhentaja]

You may get an idea from this video too if you can put up with the narration!!

This remedy did not help

Also I cant pinpoint what causes the limp mode or Engine managment fault to occur, I couldn't find any nicks or kinks on the wiring also, should not be that also. I havent been able to measure the wiring loom resistance or continuity because the wiring diagrams are bit too confusing... When fault is active the throttle body is not energized and wont respond to pedal actuation that is what I managed to find out in todays session with the baguette.

[Moyhentaja]

I will try to do this calibration procedure tomorrow:
https://www.yumpu.com/en/document/read/ ... 44-and-/19
Before starting a parts cannon to the vehicle.. that is a endless pit of money wasted.
Chapter IV and V.

Even tho car does not have BOSCH ECU, it has the Jhonson controls ECU..

[PaulC5]

If you have not checked the ecu yet then it might have some poor connections/damp - a similar topic on a Peugeot 2008 viewtopic.php?t=71029

[Moyhentaja]

If you have not checked the ecu yet then it might have some poor connections/damp - a similar topic on a Peugeot 2008 viewtopic.php?t=71029

Thanks for the reply, alltough I have cheked the ecu pins and everything is looking like it came from the factory. I even opended the ecu to look for water damage but the ecu is sealed with silicone mold..

[Moyhentaja]

OK folks, little update. Car did infact work today, cant tell if the calibration process did it but we will see. Another fault code did occur however, when the car war switched on/off while moving the central computer said "Airbag failure" or something like that and after a while it disappeared... This car is in nice condition allaround but i think it is haunted

[ozvtr]

The "fly-by-wire" accelerator peddle and throttle body in the TU3 engines are very reliable.
Faults tend to be in the wiring, the electrical connectors or the engine ECU. Look for corrosion on the associated electrical connector pins.
HOWEVER, that random airbag failure tends to point towards an electrical power supply issue.
I would look VERY scrupulously at the battery and alternator. Even batteries that are only in fair condition, can cause problems! They don't have to be dead to cause problems. The battery can only be tested correctly with a LOAD TESTER, NOT A MULTIMETER!

[ozvtr]

I just checked Ignition on, engine off the throttlebody TPM says its 9,8% open and when pedal is pressed the TPM reports 82,4%, read from OBD port. Could this be some kind of calibration issue? Should it be reading 0% and 100% ?

No. You would think so, but it doesn't work that way. There is no calibration set up for the KFV throttle (I'll tell you why in a second).
What the engine ECU is reporting at 9.8% and 82.4% is the percentage of the reference Voltage from the potentiometers in the TPS, not the percentage that it's open.
The engine ECU checks the extent of the throttle movement each time you turn the engine off. If you listen carefully, you will hear the butterfly click and clack against the stops.
The "fly-by-wire" throttle body of the KFV engines are VERY SIMPLE and therefor VERY ELEGANT, IMHO. However, it does require the engine ECU to do a lot of "jigger-pokery" to get the job done.
For the uninitiated, I'm not going into detail, but there is no "motor" or gears in the KFV throttle. At least, the motor does not rotate 360'.