2008 C3 1.1 - Error in throttle actuator control & Catalytic converter system

[dpaulico]

Hello everyone!

Recently bought a 2008 Citroen C3 1.1 (Left hand drive) with 210.000km on it. Upon driving it for around 200km, the check engine light came on warning of "Anti-polution system fault", after a bit, there was a "Defect in engine control system" and the car went into limp mode and needed to be pulled over. After waiting for a few minutes and restarting the car, the fault regarding engine control was gone, but the check engine light stayed on. The car seemed to rev correctly and provide power as expected, the only visible issue was that when pulling up to a stop and pressing the clutch, sometimes the revs would go down too much and the car would stall.
Upon connecting an OBD scanner to the car it reported the following errors:

* P0420: Catalytic converter bank 1 - efficiency bellow threshold
* P2101: Throttle Actuator motor (TAC) - range/performance problem

It was taken to a mechanic, which reset the codes, and drove it for 150km and couldn't reproduce the fault. But right after picking it up, the fault happened again, the car needed to be pulled over and restarted.

Eventually, the throttle body was replaced with a throttle body from another C3, but before that we tried cleaning the throttle body eletrical connector and leaving it unplugged for 24hr to dry in case there was any humidity in the connector

A bit after replacing the throttle body the "Defect in engine control system" fault happened again with the same OBD code P2101.

Was there a relearn procedure that needs to be done after the throttle body was replaced? Could the issues be caused by other parts? Has anyone had the same issue and can shed some light on this?

Any help is massively appreciated, as I've been stuck with this error for the past month.

[ozvtr]

The throttle system in the TU engine is very reliable, because there are very few parts to it!
The accelerator peddle uses "hall effect" sensors and are not known to fail.
The throttle body does not have a motor as such and the the only potential point of failure are the wipers on the carbon tracks. Again, very reliable.
No there is no "learning" for the system.
The only know issues are a small "adapter" electrical cable for the accelerator peddle for RIGHT HAND DRIVE cars. Yours is a left hand drive.
The only other, is the engine ECU. You don't want it to be the engine ECU.
I'm sorry but there is no easy way to diagnose this.
You could try removing the engine ECU electrical connectors and checking for corrosion/spraying contact cleaner on them.

Someone else might have an idea.

The P0420 could be a bad "downstream" oxy sensor. You will need a scan tool that can observe the waveform of the sensor output to see if its the sensor.
Most likely the catalytic converter is damaged, probably by burnt oil.

[ozvtr]

Check the green and yellow wire that comes out of the engine loom to the stud that holds the coil pack down.
See if you find a loose green and yellow wire from the engine loom on the top of the engine near the oxy sensors electrical connectors.

[dpaulico]

The throttle system in the TU engine is very reliable, because there are very few parts to it!
The accelerator peddle uses "hall effect" sensors and are not known to fail.
The throttle body does not have a motor as such and the the only potential point of failure are the wipers on the carbon tracks. Again, very reliable.
No there is no "learning" for the system.
The only know issues are a small "adapter" electrical cable for the accelerator peddle for RIGHT HAND DRIVE cars. Yours is a left hand drive.
The only other, is the engine ECU. You don't want it to be the engine ECU.
I'm sorry but there is no easy way to diagnose this.
You could try removing the engine ECU electrical connectors and checking for corrosion/spraying contact cleaner on them.

Someone else might have an idea.

The P0420 could be a bad "downstream" oxy sensor. You will need a scan tool that can observe the waveform of the sensor output to see if its the sensor.
Most likely the catalytic converter is damaged, probably by burnt oil.

My thinking here was, there is/was some actual issue with the control of air going into the engine, since it was having that issue where it would sometimes stall, and that would ruin the air to fuel mix and influence emissions which was being detected by the oxy sensor and raising that error. Do you think that is a possibility? I've also read somewhere that someone with a different car but with the same P2101 code had a MAP sensor issue, does that make sense in this model?

[dpaulico]

Check the green and yellow wire that comes out of the engine loom to the stud that holds the coil pack down.
See if you find a loose green and yellow wire from the engine loom on the top of the engine near the oxy sensors electrical connectors.

My knowledge of cars is limited. Picture of the car engine: . I understand the coil pack is what i marked in red. Is the oxy sensor eletrical connector the one I marked in blue?

[ozvtr]

The "down stream" oxy sensor has a blue connector.

The green and yellow wire is here.
I think your problem is a bad coil pack. The coil pack sends out electromagnetic interference which is induced into the wires of the throttle body and confuses the engine ECU.
If fixing the green and yellow wire doesn't solve your problem it might be the coil pack...other than that, I don't know.