C5 MAF sensor location.

[Jetjockey]

Hello.

Last week I got a fault code up which told me that I had a boost pressure sensor coherence problem with my C5, I cleared the fault and it didn’t return. This week I’ve got a P0100 fault pointing to the MAF. On both occasions it’s been first thing after starting in the morning, and whilst accelerating briskly with the engine cold. When the engine is warm this doesn’t happen.

Does anybody have a schematic of the vacuum system on the C5 so that I can try and sort this out please?
Not sure if the car has the conventional MAF sensor as the ones showing up on google don’t seem to be the correct one.

The vehicle is a 2008 C5 2.0ltr Hdi Exclusive tourer, Chassis No VF7**************[VIN obfuscated, can be read by forum staff].

Thank you.

[GiveMeABreak]

There's no 'vacuum' circuit on the MAF. It's completely electronic.

The correct part number for your MAF is: 1920HH (Note: don't be tempted to get a cheap unbranded one - they inevitably fail, are DOA or wrong). The MAF is an integral component to the engine management system.

I would get some MAF cleaner and gently clean the sensor wire (this is extremely sensitive so should not be touched or brushed with anything - just use the MAF spray).

As for the P0100 fault: Flowmeter signal: Air flow not plausible
Description: The measured air flow for 3 seconds is either:

• Higher than 800 mg/stroke at 1250 rpm
• Higher than 1800 mg/stroke at 2000 rpm
• Higher than 1300 mg/stroke at 3000 rpm and for a turbocharging pressure of 1,75 bars

The Fault is triggered: at engine speeds higher than 1250 RPM and will trigger the Engine Management Light.

Fault will disappear: Driving for 5 minutes with several full load accelerations for 10 seconds.

Downgrade Modes Whilst Fault is Triggered:

• The ECU stops the regulation of the EGR valve
• The ECU limits the flow of fuel and deactivates the cruise control (it limits the vehicle speed until the next time the ignition is switched on)
• The ECU stops the regulation of the turbocharger: Change to piloted mode

Symptoms:

• Noise
• Diesel fuel consumption a bit higher
• Lack of power

Suspect Areas:

• Electric exhaust gas recycling valve
• Air flow meter
• Air intake
• Turbocharging pressure sensor

[Jetjockey]

Thank you Marc. I realised the MAF is not linked to the vacuum system, but it does actuate to turbo.
BTW, where is the MAF located? I’ve located two sensors in the intake pipework just prior to the manifold and I’ve cleaned them. One appears to be a pressure sensor, and the other looks very much like an 1N4148 diode soldered between two pins (Air temperature?).

Also, does anybody have a schematic of the vacuum system?

Thanks.

[GiveMeABreak]

I can sort a diagram tomorrow, if it’s the air system you want in relation to the turbo.

I’ve circled the MAF in red for you.

[Jetjockey]

Thanks Marc, that would be very helpful.

Cheers.

[GiveMeABreak]

Right..

Air Supply:

Reference Designation 1 Master Cylinder 2 (/) Vacuum Pump 3 Exhaust Gas Recycling Solenoid Valve (EGR) 4 Turbocharging Pressure Regulation Solenoid Valve 5 Catalytic Converter 6 Engine ECU 7 Turbocharger 8 Boost Pressure Waste Gate (WASTGATE) 9 Air Flow Meter 10 Turbocharger Air Cooler 11 Intake Air Temperature Sensor 12 Inlet Air Pressure Sensor 13 Mixer Control Electrovalve (With EGR)

The other sensor you may be referring to is the Inlet Air Pressure Sensor:

MAF:

This is the Turbo Pressure Regulation Solenoid - it regulates and limits the boost pressure.

"m" Outlet to boost pressure waste gate (WASTGATE).
"n" Vacuum inlet (via the vacuum pump).
"p" White marking.
"q" Connector.
"r" Atmospheric pressure inlet.
The solenoid control is an OCR (Opening Cyclical Ratio) type control.
The proportional electrovalve controlled by an OCR voltage is connected to the following components:

• Atmospheric pressure
• Vacuum supplied by the vacuum pump

The pressure supplied by the electrovalve is included between the atmospheric pressure and the vacuum pump vacuum.

[Jetjockey]

Brilliant!

Out of curiosity..... what is the valve type item in the diagram, across from the air pressure sensor? It appears to be fed with a vacuum pipe and is affixed to the inlet manifold. You can just see the top of it in the diagram.

Thanks.

[GiveMeABreak]

That's the Air Doser: Number (7) below.

[Axa]

Hi all. I'm struggling with occasional sudden jerking mostly one or a few km from cold starts. And also complete stalling, but starting up fine again after a few seconds.
First thought it was a bad accelerometer switch as I've had some fault codes about throttle position earlier. And jerking supposed to be a likely sign.
However that code have not been showing up lately, Instead there's ac fault code about MAF sensor circuit.

EGR is blanked off and FAP is out (in desperation from keeping the car running for a while until Korona blows over so I can afford something better..)

I've measured over the MAF signal cables just over 2Volt at idle, and up to 2.4V.
Is this the correct range? Or an indication the sensor should be cleaned or replaced?
Maybe in shold measure also under load when driving?

Will get some MAF cleaner later this week in hope that will help, but would be nice to know what range the signal should be?

[GiveMeABreak]

Sorry, I can't help you as you've removed the DPF and blanked the EGR which is something we do not condone. As a result this will affect the running of the engine as the Engine ECU expects these devices to be there, so troubleshooting is going to far more difficult as a result of you doing this.

[Axa]

I suspected that. Unfortunately my driving pattern in winter time doesn't work at all with a filter. I wish I knew this weakness before I could not afford to sell and get something reliable. Today the sales value on the car is less the cost of getting a new FAP fitted and eolyse refilled. And in these times my only option is to keep the car running, or buy an older less safe and/or probably less environmental friendly non FAP car. So I must say I'm a bit puzzled on why removing this obvious crap system is picked upon. But rules is rules so I can also understand why a forum might be forced to...

[GiveMeABreak]

So I must say I'm a bit puzzled on why removing this obvious crap system is picked upon. But rules is rules so I can also understand why a forum might be forced to...

Because it's illegal to remove emissions control devices for vehicles on public roads here - and I'm quite sure it's the same in all EU countries. Apart from the obvious pollution and health issues that particulate matter causes, you can be heavily fined and your car insurance possibly affected or voided as you have modified the car from its original certification by removing it.

Your vehicle may also fail the equivalent MOT (Periodisk Kjøretøykontroll) becasue of this - which is going to cost you anyway.

[Axa]

I know about all that.
Also there plenty of old non FAP vehicles around here out in the countryside. Luckily also an increasing amount of Tesla's and other electric cars.. Partially running on East European coal powerplants.
Again, If my car fails MOT I will be forced to buy something even worse when it comes to pollution. These rules only suits the ones that can afford to follow them. Or are lucky to have a daily driving pattern that suits modern diesels... If I lived in a city I would think differently, and could probably get along with a small cheap electric car. But where I live that would not work at all..
One thing is for sure. I will NEVER buy an DPF vehicle ever again.
I've been dreaming about an old diesel that could run on frying oil. But that would only work in the summer..

[GiveMeABreak]

I understand what you are saying, but there's no longer any excuse not to replace them now, as they are far less expensive than they were 15-18 years ago.

A DPF for a 1.6 C5 can be bought for just over £100 now....

[Axa]

So how often would I have to replace during winter when engine never get warm enough for regeneration?