error: signal air mass meter C5 R

[gorgar]

Hello all,

Many greetings from a Citroen owner from Germany. I'm asking for your help because I'm not getting anywhere on my own.

My problem concerns my C5 II, diesel, 2.0 HDI 136 hp, built in 2006.

During the exhaust emission test at the due TÜV, there was an error message, which is why the test was cancelled:

Fault memory contains exhaust-relevant fault

When reading out the Diagbox with Lexia (Citroen software) I found the following errors:

- permanent error: signal air mass meter frequency too strong minimum quantity
- constant error: signal intake air temperature mass air flow sensor CO or CC Plus (+)

The constant error in the Diagbox can be deleted, but it comes back. Replacing the mass air flow sensor with two different new parts did not change anything, and disconnecting the plug did not change the running of the engine.

The following warnings appear in the display more often: ESP defective and/or exhaust system defective. But they can be deleted again.

Otherwise, the car runs perfectly and consumes 6.2 l/100 km, which is normal.

I can't get through the MOT like this. Does anyone have any ideas? That would be nice..

I hope the translation from Deepl fits.

Many greetings and thanks in advance

Norbert





Translated with www.DeepL.com/Translator (free version)

[GiveMeABreak]

Hi Norbert

If you have the actual fault codes that were shown in Lexia / Diagbox, I'll have a look to see if there are any pointers. Also please pop the 17 character VIN number here, so I know the exact vehicle and systems.

[gorgar]

Hi Givemeabreak,

thanks for your answer.

The VIN is VF7**************[VIN obfuscated, can be read by forum staff]

My knowledge is limited, unfortunately, I don't know which values are ok and which are not (except that -40 degrees Celsius can't be right ).
I have done the global test with the Lexia as well as some error queries. How can I dend you pictures. Thea are on my PC.
Is that enough for you? Otherwise I can make more queries plus photos, tell me which ones...

Many greetings

Norbert

[GiveMeABreak]

Norbert, just provide the actual fault codes for these errors - you are missing the actual code from the beginning, for example P0101 or P0112. I can't tell from the description because it has been translated and there are a lot of possibilities. If you can provide just the codes for the faults, that's all I need.

- permanent error: signal air mass meter frequency too strong minimum quantity
- constant error: signal intake air temperature mass air flow sensor CO or CC Plus (+)

That's all I need as I have the VIN now.

[gorgar]

P 102 , P 0113

Temperature mass airflow sensor -40 degrees Celsius (!!..) Outside temperature + 7 degrees C.

[GiveMeABreak]

So the most common problem would appear to be your Mass Air Flow Meter. Especially if it is giving wildly incorrect readings.

Fault Code:	P0102
Description of Fault:	Flowmeter signal : Measured flow less than the minimum flow. The signal issued from the sensor is outside the electrical tolerance (Frequency too high). Conditions of activation of the diagnostics: Battery voltage more than 7,45 V
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	The engine ECU no longer regulates the EGR valve.
Symptoms:	Lack of power
Suspect Areas:	Air flow meter Electrical harness

Fault Code:	P0113
Description of Fault:	Inlet air temperature sensor signal fault : Open circuit or short circuit to the plus. The voltage of the signal for air temperature at the flowmeter is higher than 4, 8 V for 5 s.
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	Cutting of the diagnosis of plausibility of the flowmeter.
Symptoms:	Engine hesitating, cutting out Lack of power
Suspect Areas:	Air temperature sensor on the flowmeter Electrical harness Connector Engine ECU

[gorgar]

Thanks!

[cit-rotti]

According to the wiring diagram, the following data results from the (probable) wiring of the LMM and where the wires lead to. And the diagram does not always fit 100%.

The LMM (1310) should have a 4-pin grey connector (4V GR).

No1) (1339) goes to the engine control unit (1320) via the 32V NR connector to terminal H3 (should be ground from the control unit).

No2) (1340) goes to the engine control unit (1320) via the plug connection 48V MR to the terminal C1 (should be control line)

No.3) (1336) goes to the engine control unit (1320) via plug connection 48V MR to terminal G2 (should be control line)

No.4) (120C) goes to the BSM via the 28V NR connector and should be protected by fuse F10 in the BSM.



Check the sequence on the LMM connector - the numbers are usually/often printed on the cable. After that, lines 2 + 3 are the control lines to the engine control unit for the temperature signal and air mass signal.
No. 1 should be the ground from the control unit and
No.4 is the + which comes from the BSM and is fused there. Sometimes the fuse is blown and often only one contact point on the plug is defective.

Around the LMM the +voltage and the ground of the engine control unit should be checked with a multimeter. A test lamp can also be used around the BSM.
Measure the control lines with a multimeter or oscilloscope - this should be done by someone who has experience with LMM tests.
Since it is possible that there is only a voltage supply problem, troubleshooting should start here first. It is important to find the right wires and check them.

Greetings Wolfgang