Dean_

Egr wiring tests

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I have 1.8 tdci with an egr fault.

I have so far tried new egr motor, new egr valve assembly and I still have fault code p0406 coming up so I'm thinking it's either wiring or another sensor giving wrong information to the ecu? 

At the moment I have to run with a egr blanking plate in other wise I have no power. The valve is free moving, clean and de coked.

Any suggestions, test procedures, test voltage and resistance readings or wiring diagrams would be greatly appreciated 

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8 hours ago, Dean_ said:

have so far tried new egr motor, new egr valve assembly and I still have fault code p0406 coming up so I'm thinking it's either wiring or another sensor giving wrong information to the ecu? 

At the moment I have to run with a egr blanking plate in other wise I have no power. The valve is free moving, clean and de coked.

Any suggestions, test procedures, test voltage and resistance readings or wiring diagrams

The original EGR actuator on my 2006 1.8 had a basic electric motor and a pot (potentiometer) for position feedback.

The motor is on pins 1 & 5, and should have very low resistance (<2 ohms) with a multimeter, but the reading will jump about violently if the actuator quadrant wheel is moved by hand, due to motor back EMF. But it should settle back to a low resistance whenever the movement stops.

The Pot is between pins 6 and 2, with the pot wiper on pin 4. My pot was about 5k end to end, and the wiper resistance varied between about 1.5k and 3.5k as the quadrant wheel turned.

You can also test the motor by applying voltages up to 12v to it (1 = +, 5= -), ideally with a variable power supply. It has a spring return, so power off should always make it snap back to the closed position. (The drawing shows 1+ & 5-, but my hand scribbled notes seem to say 5+, 1-, but a bit of reverse power will not damage it, just won't move.)

The Chinese EGR actuator I replaced my dodgy old Ford one with this year, has an electronic sensor. Resistance readings are almost meaningless. At first I though it was duff, but when 5v was applied to pins 6 & 2 (2 = +), it sprang to life and gave a sensible voltage output on pin 4, just like the pot version would with 5v applied across it. In theory an electronic sensor may be better than a mechanical pot, but it all depends on the quality. It is Chinese, so I will wait and see! The actuator is in a tough location, high temperatures and massive vibration are the norm.

I have been repairing mine since 2012, it worked for a while each time, then started playing up again in a year or so. So I am very familiar with its internals. Though only the actuator, I have not had the inlet manifold off to check the valve part. But that has always seemed to move smoothly.

I have done a post somewhere with pics, but have lost it. I will look a bit more later. I can find it via the attachments.

 

 

 

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9 hours ago, Dean_ said:

wiring diagrams

Found the post:

 

Also there is a diagram of the valve & connector:

1-8-EGR.PNG

All 5 wires go straight to the ECU. Though I suspect they may go via that big connector on the back of the engine. The wiring diagram does not show that one.

I have just noticed your car is S-Max, so wiring colours may differ. But I suspect most engine bits are the same. ECU software may be a bit different though. Please let me know if there are obvious differences.

Since you have changed the valve & actuator, either there is a fault in the new actuator, or there is a fault in the wiring, or even (hope not!) in the ECU.

With the actuator removed from the valve, but plugged back in to the car wiring, you can see the power off test. Just cycle the ignition on then off. It should do a series of full actuations, probably to clean the valve, then hover in one or two places, then snap shut. I have a feeling that this test is what puts the EML on if it fails, it seemed that way on my car anyway.

The EML is still not an MoT fail on a 2006 diesel, but a visible blanking plate in the EGR might be, though only if an eagle eyed tester spots it and knows what it is!

Regarding other sensors, does the EML & DTC appear when blanked? On my car I could still get errors while blanked off. That rather narrows it down to the EGR valve.

When blanked, the valve is almost always either full shut or full open while driving. When not blanked, it mostly hovers in mid travel while idling and cruising. It closes in over-run or at more than about 50% of full power, or at over 2500rpm. The sensors that control this are the MAP, IAT2 and the MAF. The airflow through the engine can be estimated from MAP, RPM and intake air temp (IAT2) in the air duct just before the manifold. This estimate includes the EGR flow. The MAF measures air into the system, prior to EGR flow. So the difference should be the EGR flow. However this is rather approximate, subtracting a rather imprecise MAF reading from a complex computed estimate is obviously dodgy. Since I get no errors when the valve is blanked off (if the actuator is working ok), and the ECU knows this as it drives the EGR hard open to try to get the flow it wants, then it seems the ECU accepts the error. But it does not like it when its power off test fails, or the pot reading does not match the motor drive voltage.

 So the above rather complicated paragraph means that I think most EGR DTCs on this engine are directly related to the valve or its wiring.

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Thanks for all the info,  I will have a pike around this weekend and let you know what I find 

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Just to add I have ran with egr blanked for sometime with no fault codes so presume it is a fault with he valve or wiring rather than a lack of egr flow being picked up by other sensors 

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Also do you know and volt reading that should be supplying the actuator or and tests for the loom? 

Thanks again 

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36 minutes ago, Dean_ said:

do you know and volt reading that should be supplying the actuator

The motor is a 12v unit, though about 3v is enough to start it moving, and 6v to 10v is enough to move it all the way, just against its internal return spring, if I recall. The output from the ECU will be a 12v nom. (14v more likely in practice) PWM signal, at about 1kHz from the tone I can hear when it is operating, but a multimeter will read the average voltage, which is what the motor also responds to.

Testing the loom can be a pain, as the connector at the ECU is usually protected by a security bolt, and I do not have a diagram for an S-Max ECU. If it is the same ECU as in the Focus, (Siemens/VDO), then there is a diagram on this site, and I can find pin numbers etc.

Back-probing the EGR connector while connected and running may yield some clues. Also Forscan can read the EGR desired position, though on my car I don't think it can read the EGR pot feedback signal for some odd reason. I can give more info on Forscan if needed. It is probably the most capable DIY system that is available for Fords.

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So had a quick look at the the old original actuator last night and when I opened it up in was full of carbon dust, once cleaned I could then power the motor on the bench and it would return when power was removed. But when I plugged it in to the car and left loose I still had no moment at any point???? 

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1 hour ago, Dean_ said:

I could then power the motor on the bench and it would return when power was removed. But when I plugged it in to the car and left loose I still had no moment at any point???? 

Mine moves when the ignition is turned off, even if the engine is not started. It should move within a minute or so of starting the engine also. It sounds like a wiring fault. Does you car have that big connector next to the EGR valve?

CAR-EGRE.JPG

If so the wiring probably goes via that to the ECU. I have no diagram of it, but it should not take too long to do a quick continuity test on all connections to find the EGR ones.

It is just possible the feedback pot is giving a high signal, which is preventing the ECU from energising the valve, but that should cause an error code. To measure voltages on live wiring on the car, google back-probing, if you have not already done so.

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Quick update, I haven't had time to do any back probing but with the new actuator still fitted I did disconnect the battery for an hour to see if it would reset and parameters and fingers crossed it is yet to throw the  eml back on. I am still running with the blanking plate in as it drives alot better like most cars do when the egr is blanked off. 

So hopefully my problems are sorted. Tanks for all your help Peter. Greatly appreciated! 

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Unfortunately, bad new, the eml has come back on with egr related code. Peter, if you have any spare time would you be able to give me voltage readings for each pin off your cars egr loom plug both when running at idle and just Ignition on engine not running.

Thanks again 

 

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6 hours ago, Dean_ said:

would you be able to give me voltage readings for each pin off your cars egr loom plug both when running at idle and just Ignition on engine not running.

I had a look at quick look at parts lists for the S-Max & Focus, and although the EGR, Injectors and fuel pump are all common, the ECU has a different number. So there may be some detail differences. From one photo, it looked like it was a completely different unit, but a wider search shows them both to be the Siemens / VDO part, so the difference should not be great.

I can be 99%+ sure of the position feedback readings:

Vref (2) is +5v steady, running or just Ign on. (I would expect it to be pretty close, say 4.8v to 5.2v).

Vgrd (6) is 0v steady, running or just Ign on. (again pretty close, +/- 0.2v from battery negative).

Vout (4) is typ 0.6v steady, engine off, Ign on. This will vary rather more, say 0.4v to 0.8v, it depends on just where the valve closed point is, and may change a bit within that range each time the valve moves and then returns to rest. But it should be a steady reading while the valve remains closed.

Vout will be much more variable once idling. Typ 1.5v to 3.5v I would say. The valve is almost constantly moving to try to maintain the desired flow rate. Unless EGR is blanked, when it will be 3.5 to 4.5v, and fairly steady, as the valve is driven full open.

Also the valve may remain closed for a few seconds to a minute or so right after a cold start.

The importance of the steady reading is that a varying reading while it is expected to be steady would indicate a bad connection.

The motor drive signals (1 & 5) I am not so sure of, and they could vary with ECU type. I have measured the voltages needed to drive the motor, but not on the car. I would guess one of the lines will be near battery positive while Ign is on, and other will be driven to a lower voltage to energise the valve. But it is possible that it will be the other way round, one line near battery negative, and the other driven to a higher voltage to energise the valve.

What I can say is that the voltage on both lines will be the same (both ground or both battery positive) with Ign on & engine off, and at any other time while the valve is closed.

Also when the valve is operating (engine idling), there will be a rather variable voltage of 2v to 4v between the two.

I have just re-checked my old (OEM) EGR actuator. Pin 5 is +ve, and Pin 1 is -ve, to drive the valve open. And the voltage to drive the motor is lower than I thought, 3v was enough to move the actuator to the fully open position.

 

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Just a quick update, sorry it's been so long.

With gentle persuasion you can remove the brass internals of the egr hosing to clean the back side of the valve. Just make marks before removing as it has to be in the correct rotation otherwise will confuse the control motor.

Many thanks to tdci-peter for all the information and help, much appreciated 

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18 hours ago, Dean_ said:

With gentle persuasion you can remove the brass internals of the egr hosing to clean the back side of the valve.

Was this the brass bit you managed to remove:

CAR-EGRA.JPG

It looks quite well peened in to me, but might come out with the right sort of persuasion, maybe?

Did cleaning the inside of the valve cure the problems?

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