C3 P0402 EGR Excessive Flow

[MikeT]

The freeze-frame data of this returning permanent fault appears to contradict the error code or am I missing something (I usually am!).

[Stewart(oily)]

Check the vacum hoses. has your EGR been nobbled?

[wheeler]

If the Measured air flow is higher than the expected value then it looks like the EGR valve is jammed closed (would expect to see copy position faults in this case) or the EGR valve is blanked off.
What is the airflow readings when the engine is idling & fully warmed up ?

[MikeT]

There's far less data than my C5 provides but what I have seen so far is EGR valve OCR% (at 5%) and no sight of any copy signal.
Lexia also shows EGR throttle OCR% (0%) which I believe is not fitted to this engine.
I'll get more data on next run out.

[EDC5]

Doesn't the EGR throttle refer to the butterfly valve just before the inlet manifold?

[MikeT]

Doesn't the EGR throttle refer to the butterfly valve just before the inlet manifold?

That's my understanding Ellis. I looked in the engine bay and saw nothing obvious and Citroen Service shows no such part either so assume it's an erroneous parameter.

[MikeT]

To be honest, I was more doubting what little sanity I have left but if "Excessive EGR Flow" in this case actually means "Insufficient EGR Flow" then I'm good!

[wheeler]

The airflow readings from the MAF are the ones im interested in, they are a good indicator of what the EGR is actually doing.
The OCR% readings are what the ECU wants it to do.

Thought it was an electric EGR valve on this engine so wont be any copy signal on it unless there are wires coming off the EGR valve itself, in this case it uses the MAF to know what the EGR valve is doing.

[GiveMeABreak]

This is what I have for this fault Mike: As you already know, you have the Siemens Injection System. This fault info is as listed for this Engine under your C3 and not a generic description.

Fault Code	P0406
After sales description of the fault code	Exhaust gas recycling electric valve position copy signal: Copy voltage too high
Main customer complaints likely	Switching on of the diagnostic warning light; Noise: Cold
Back-up mode following returning of the faults	The engine ECU cuts the regulating of the EGR (*); Programming status of the exhaust gas recycling valve
Conditions for returning of the fault	When the valve is controlled: The fault codes are returned immediately in the engine management ECU; The diagnostic warning light only comes on and switches off after 3 engine starting cycles (**)
Suspect Areas / Faulty Components	Engine ECU 5V shared supply; Electrical harness; Exhaust gas recycling valve
Appropriate Tools	Adaptor harnesses; Multimeter; Controlled Terminal Box (in manual mode) or Manual Terminal Box
Engine Concerned	DV6, DV4 Bosch, DV4 Siemens, DW10B Siemens, DW10B Delphi, DW12B Bosch

Notes:
(*) Consequence for the parameter measurements:

• OCR controlling the electric EGR valve = 0 %
• Position repeat = 0 %

(**) 1 Starting cycles:

• Engine start
• Engine cut-off
• Wait for the instrument panel to switch off

[GiveMeABreak]

I'll get you the fuel system setup in a second which may help identify what it and isn't on the vehicle...

Electrical Circuit

Component	Reference	Remarks
Diesel Injection ECU	1	-
Engine Speed Sensor	2	Tightening torque: 5 m.daN (min.) and 10 m.daN (max.) Black 3-way
Position Sensor (A.A.C)	3	Adjust the airgap of the camshaft position sensor 1,2 mm Grey 3-way
Engine Coolant Temperature Sensor	4	On the coolant outlet housing
Vehicle Speed Sensor	5	-
Atmospheric Pressure Sensor	6	Incorporated in the injection ECU
Battery	7	12 Volts
Injection Double Relay	8	Integrated with the engine fusebox
Diagnostic Warning Lamp	9	Incorporated in the instrument panel
Centralised Diagnostic Socket	10	Passenger compartment interior
Transponder	11	Transponder integrated with the BSI and engine ECU
Consumption Information	12	Incorporated in the instrument panel
Tachometer	13	Incorporated in the instrument panel
Heating Warning Lamp	14	Incorporated in the instrument panel
Pre-Post Heat Box	15	-
Pre-Heater Plug	16	-
Accelerator Pedal Sensor	17	-

Fuel System

Component	Reference	Remarks
Fuel	18	Diesel
High Pressure Fuel Sensor	19	-
Fuel Tank	20	Capacity = 45 litre Composition = Polyethylene
Fuel Filter	21	-
Low Pressure Regulator	22	Fixed to the high pressure fuel pump
Fuel Cooler	23	-
Fuel Heater	24	Integrated in the fuel filter cover
High Pressure Fuel Pump	25	The high pressure fuel pump is driven by the timing belt
Fuel High Pressure Common Injection Rail	26	-
Diesel Injectors	27	Piezo-electric controlled diesel injectors
High Pressure Fuel Regulator	28	Fixed to the high pressure fuel pump

Air Circuit

Component	Reference	Make	Reference	Remarks
Air Flow Meter	29	SIEMENS	39071LS.F	-
Air Cleaner	30	MECAPLAST	50557LP.A	Incorporated into the inlet manifold
Turbocharger	31	KKK	Type KP35	-
Exhaust Gas Recycling Valve (EGR)	32	SAGEM	Type 2580132-A	-
Recycling Regulation Electrovalve (EGR)	33	-	-	-
Exhaust System	34	-	-	-
Vacuum Pump	35	-	-	-

[GiveMeABreak]

Here's the EGR - doesn't seem to be electrically operated for this part (1628XV), but what about the electrovalve (number 33 on the diagram)?

[MikeT]

Following a 15 mile round trip the results are....
Air flow matched Referenced flow almost to the digit throughout all driving ranges while the EGR commanded OCR% value never deviated from a constant 5%.
Although I do not have P0406 registered, todays data does appear to show the ECU backup mode of cutting EGR regulation.
Guess I should have cleared the fault first?

Yes it does have the EGR regulation valve (33) fitted to the front left side of the engine with all connections in place.

[GiveMeABreak]

So is there sufficient vacuum being generated Mike?

[MikeT]

I really don't want to have to test it at this point if it's not necessary. Besides, if the ECU has cut regulation and as the live data shows a fixed OCR 5% then I would expect to find no vacuum supplied to the EGR valve anyway.

I think i shall just have to wallow in my ignorance and leave it closed.

[white exec]

That's a lot of data to digest, Mike.