Peugeot 307 1.6hdi p0402

[vnechev]

Purchased a 1.6hdi some time ago and have been trying to pinpoint the cause of a p0402 which will not allow the regeneration of the dpf. Changed some parts on it like the turbo oil feel pipe, had the turbo checked and it seems to be spinning freely. Changed the vacuum solenoid thats at the back of the bulk head, and the MAF sensor with a brand new pierburg and the error keeps showing up. I’ve ran some live data screenshots and was hoping direction on the cause based on the screenshots. I’ve been told to remove the dpf which i dont want to do, or to change the turbo.

VF3**************[VIN obfuscated, can be read by forum staff]

[RichardW]

P0402 seems to be excessive EGR flow. What is the EGR valve position doing vs the reference value? What is the air flow vs the reference value?

[GiveMeABreak]

Fault Code Info (bit of a lottery on the suspect areas though ):

Fault Code:	P0402
Description of Fault:	Air system fault: Measured quantity of air lower than the setting. Positive gap for 10 seconds between the theoretical air flow and the calculated measured air flow. Conditions of activation of the diagnostics: The following conditions have to be met: - Consult the associated contexts for the Pcode forwarding conditions - Engine speed between 750 and 2750 rpm
Conditions for Fault to clear:	Vehicle driven for 5 minutes, remaining below an engine speed of 3000 rpm
Downgrade Modes whilst Fault is active:	Deactivation of diagnosis of coherence on the flowmeter Cutting of the EGR butterfly (turbo air cooler), EGR valve and bypass butterfly (inlet air heater) in all operating modes Cutting of the "exhaust heat recovery" function Limitation of engine torque Cutting of cruise control Switching on of the warning lamp and/or warning message: Warning lamp MIL
Symptoms:	Noise Diesel fuel consumption a bit higher Lack of power Starting problem
Suspect Areas:	Exhaust gas recycling valve Air leak between the air flow sensor and the compressor Obstacle hindering the passage of the air Air flow sensor information incorrect Vacuum problem Variable geometry of the turbocharger jammed in the "minimum turbo" position Principal air meter Air flow meter Turbocharger Variable geometry of the turbo + vacuum circuit Turbocharging pressure sensor Clogged air filter

[vnechev]

Thanks Marc, that's definitely a lottery to try and figure out where it is. The error takes a while to come up, and my filter housing is not in great shape. The pipework for the fresh air, doesn't attach real well, however, the maf and the pipe going to the turbo from the maf is attached pretty good with a new pipe and seal.

I changed out the EGR since i did not have diagbox when this error initially came up, and googling p0402 usually points to EGR fault. Changed it with a new Nissens EGR, the original was a bit dirty, and i think that's due to the car not being able to regenerate for a while.

Originally the car had a P1251 - Pre-heating relay circuit , Relay supplied and plugs never supplied error. The glow plugs hadn't been changed and were the original, so I changed them, and that error went away.

Is the principal air meter an actual sensor ? I was thinking of replacing the Turbo charger pressure sensor but not actually getting a code for that.

[johnfish2017]

is this just a change of sensor doesn’t go into limp mode or a thing ?

[vnechev]

Im starting to think it might be. I ordered a Hella 009400521 boost pressure sensor and just waiting to make my way back overseas in july and see if it resolves the issue. Otherwise I might have to smoke test the pipework or even dismantle it all to see if theres an obstruction. Hoping I wont have to replace/recycle the turbo.