P0134, P0136, P0138 - check engine lights up

[ayhan4ik]

Hello everyone,

My wife is driving C3 in 2004 (1.4i KVF) for about 2 years. Since we have it, it lights P0134, P0136, P0138 error codes, all referring to O2 sensors. Errors are cleared, but after about 2-3 days, they come again and the check engine lights up. This does not affect any way of driving, dynamics or idling. I can not judge if it affects the fuel usage. Most likely yes, because sometimes I feel a slight odor of unburnt petrol at the back.

More than a year ago I replaced both probes (they are not original but correspond to the same part number with the original ones). The change did not solved the problem.

Last spring I picked up a part that swooped on the second probe to emulate the signal and make something like a bypass:

And that did not solved my problem.

Last time, I was in a garage where they told me that the problem was actually a dysfunctional "secondary air pump":

Which, as far as I know, really affects the readings of the oxygen sensors, but interestingly, so far, I have not had any error concerning that pump.

I'm determined to put the car in a normal mode of operation (no errors), but I need some help.

I will expect your opinions. And here's what Lexia gives me at the moment:

[Arfur Dent]

My wife is driving C3 in 2004 (1.4i KVF) for about 2 years. Since we have it, it lights P0134, P0136, P0138 error codes, all referring to O2 sensors. Errors are cleared, but after about 2-3 days, they come again and the check engine lights up. This does not affect any way of driving, dynamics or idling. I can not judge if it affects the fuel usage. Most likely yes, because sometimes I feel a slight odor of unburnt petrol at the back.

More than a year ago I replaced both probes (they are not original but correspond to the same part number with the original ones). The change did not solved the problem.

Hi ayhan4ik. You have 2 codes, an upstream and a downstream. It is unlikely you have 2 faulty sensors unless there is a common problem like contaminated fuel.

The codes don't say the sensor is faulty, it says the signal from the sensor is not as expected. Changing the sensors probably won't fix this.

I'm determined to put the car in a normal mode of operation (no errors), but I need some help.

Start by looking for a common denominator between upstream and downstream. Like 12v power to the sensor heaters, which would be a common fuse/supply. So check the condition of fuse F15 in the BSM (engine bay fuse box) tips-for-any-citroen-c3-f8/c3-2002-to-2 ... -t157.html and if you can measure voltages at the upstream sensor?
The output is tiny and an oscilloscope is often used to read the switching output.


Your coolant is at 40° C when you took lexia screen shots and the sensors are still in open-loop mode. Did you get the car up to temperature before getting the error codes, because you may have a faulty temperature sensor blocking the closed loop (feedback loop) mode.

There are often 2 temperature sensors and one can go faulty without affecting the dashboard but is will play havoc with the engine ECU.

(although I have just seen one at 87 ° C, but it may be an intermittent faulty sensor?) worth checking anyway.

[Citroen-Driver]

Hello everyone,

Last time, I was in a garage where they told me that the problem was actually a dysfunctional "secondary air pump":

Which, as far as I know, really affects the readings of the oxygen sensors, but interestingly, so far, I have not had any error concerning that pump.

Hello

I don't know what that part is on the KFV engine, maybe something for a specific region?

Is it attached to the exhaust manifold?

If there is an air leak into the fuel air mix - aka an unmetered air intake, you get a weak mixture and this can affect what the O2 sensors expect to see.

[ayhan4ik]

Ok. I had few free hours during the weekend and decided to spend them of my wife's C3.
First of all I've started with that secondary air pump thing. I've disconnected it and I saw a lot of oxidation in the connection. It was wet, so it's a water ingress.

It's miss functional, as it's impossible to work with this connection. I've scanned with Lexia and there were no codes after disconnection, which means that it's not linked probably to the ECU somehow. Then I've closed the air pipe which goes to the engine. Driven the car little bit and it goes like charm. So I left that pump aside.

Then I've disconnect the ECU connectors and checked them carefully this time.
The problem can be clearly seen, below in the photos. The pin 1 & pin 2 are corroded and most probably there is intermittent contact now.

I wonder what are that circuits are responsible for? Can anybody help with this info?

In the meantime I'm planning to remove the corroded terminals in the connector (if I can find a tool to do it) and change them if possible. Are you aware of any other method to remove corrosion and increase conductivity?

[C3driver52]

Driven the car little bit and it goes like charm. So I left that pump aside.

Hi ayhan4ik, great work. I don't think the C3 needs this pump to work, but maybe a local emission law needs is?

In the meantime I'm planning to remove the corroded terminals in the connector (if I can find a tool to do it) and change them if possible. Are you aware of any other method to remove corrosion and increase conductivity?

Try this topic by user1234 - Improving poor ECU plug connections and conductivity on a Citroen C3.

Then I've disconnect the ECU connectors and checked them carefully this time.
The problem can be clearly seen, below in the photos. The pin 1 & pin 2 are corroded and most probably there is intermittent contact now.

I wonder what are that circuits are responsible for? Can anybody help with this info?

I am going t guess it is the secondary air-pump
But I will get a more definite answer later today.

[C3driver52]

Citroen C3 ECU plug

Hi ayhan4ik

I can find H1, its is an earth but I can't see G1, so I will need the VIN number to identify the particular version of your TU3 down to an exact one so I can see the right diagram.

You can PM me the VIN or post it here

[ayhan4ik]

Your support is really appreciated! Here is the VINVF7FCKVFC26887255.

[C3driver52]

Your support is really appreciated! Here is the VINVF7FCKVFC26887255.

I tried VF7FCKVFC26887255 and it comes back as 'vehicle not found' or 'error in VIN'

Can you double check it please?

[ayhan4ik]

Strange...

[C3driver52]

Strange...

IMG_20190305_192604.jpg

Thanks for checking.

Yes, very strange.

I tried the VIN again today, just in case there was a glitch in the system but again it comes back with an error

So I checked the image you gave and it is different than the code you gave

Image shows VF7FCKFVC26887255 so I will check that for you.

DEPOLLUTION MOTEUR IFL5 EURO 4 (INCITATION FISCALE)
"PULSAIR" AIR INJECTION <<--- the bit giving you trouble
INJECTION ECU: SAGEM