EGR Valve Fault

[Klaus Ludwig]

Hi @Crasher, Current thinking is that we could introduce a temporary earth connection at T6/3 and see if this allows the EGR valve to operate. Any feedback on that idea appreciated. I'm assuming that the ECU may not give the appropriate pulse width modulated signal to the motor unless it has an expected position feedback.

 

[Uwe]

We currently have no idea of where exactly to look for the open circuit fault between T6/3 and earth.

How about running a new ground wire from a known good point wire to T6/3? That might not be a "correct" repair, but it's ease & cheap, and it would go a long way toward validating your diagnosis that a bad ground connection is the cause of the problem.

-Uwe-

PS: You just beat me to it!

 

[Klaus Ludwig]

Weather permitting will give it a try tomorrow. It's around 23:20hrs in the UK now. Will be brilliant if it works and given that the car is not far off 13 years old we may decide that we can make this a "permanent" repair if it works and access to the point of failure is likely to be awkward. We were very close to sending the ECU off for repair. Had already booked the courier to collect tomorrow. Have now canceled the courier pending further checks! Would be lost without VCDS and also without this forum.

 

[Crasher]

The welded connection (actually spot welded copper) is usually only a few inches into the harness from the ECU, I have a picture of it on a CC that I suspected of having an ECU fault but I could not guarantee a fix so the customer bailed, unfortunately I can't find it.

 

[Klaus Ludwig]

Thanks @Crasher,

That at least gives us a clue of where earth 85 might be - and narrows down where to look.

Our EGR valve T6/3 DEFINITELY has no continuity to earth. The CBDC Current Flow Diagram shows that T6/3 should have continuity to earth. We did have continuity from T6/3 to T60/53.

Also confirmed we did have 5 volts on T6/1.

We tried basic setting of the EGR valve with a temporary (and proven) earth fixed at point T6/3. This did not make any difference at all. The EGR valve still barely moved. Unfortunately we don’t have any means (e.g. oscilloscope) of confirming the state of the pulse width modified signal to the EGR valve motor. Only have a digital multimeter with insulation resistance capability. The digital multimeter obviously gives us an overall idea, but doesn’t tell us if the PWM signal looks normal. We did not measure the voltage across the motor during basic setting or output tests.

Based on findings to date we have reversed the decision on the ECU and have sent it off for checking.

My understanding of the VCDS basic setting function is that it goes through some kind of calibration process (in this case essentially zero and span). I note that there is basic setting for the EGR valve (ignition on & engine off) and that there is also a basic setting (engine on) for the EGR system “modulation” which I would assume one does after the basic settting of the EGR valve. Any comments on my understanding of VCDS basic setting functions appreciated. We did not get any indication of a pass or fail at any time.

We are not sure if the ECU EGR control is self tuning. If it is then possibly the “engine on” VCDS EGR basic setting may not be essential after EGR valve calibration (basic setting)?

The readings we were getting in the 4 measured value fields whilst attempting to carry out a basic setting of the EGR valve were not as expected. Field 2 contained binary code at times and field 3 contained only binary code. I am guessing that this behaviour might be caused by “out of range” readings which in turn can be caused by poor connections or a faulty ECU or indeed a faulty EGR valve – though in our case we are getting similar results with a new EGR valve.

The link below is a video taken of the our attempt at EGR valve basic setting. Note the readings in the middle two fields. Currently suspect we have an Engine ECU issue.

https://www.dropbox.com/s/wrv99ckbxp3oak9/K1.MOV?dl=0

Any feedback/comments from anyone appreciated.

 

[Klaus Ludwig]

Further update, the ECU company we chose was unable to complete tests of our particular Engine ECU and is returning it so we will have to find another way forward.

 

[Crasher]

I even tried Bosch in Germany and they let me down

 

[Klaus Ludwig]

I believe that Bosch in Germany currently have a turn-around time of around 3 weeks and we can not be certain what the end result will be. They will also not deal with "end users" so we would presumably have to do via a specialist. A new ECU supplied, fitted and programmed is not far off £2000 via a local main VW dealer who do not do exchange units for our particular ECU.
Any other feedback on my previous message appreciated.

 

[stylers]

I believe that Bosch in Germany currently have a turn-around time of around 3 weeks and we can not be certain what the end result will be. They will also not deal with "end users" so we would presumably have to do via a specialist. A new ECU supplied, fitted and programmed is not far off £2000 via a local main VW dealer who do not do exchange units for our particular ECU.
Any other feedback on my previous message appreciated.

If there were an open circuit on the EGR valve motor/solenoid you should get a separate code for this. This EGR valve motor/solenoid has two wires back to the ECU. the position sensor voltage also goes back to the ECU and should have a voltage of somewhere between 0.5 - 0.7 volts with the valve closed. if you disconnect the valve plug, you should see both the codes for the motor / solenoid circuit and the position sensor. This would usually prove the wiring somewhat ok. But double check for continuity back to the ECU plug. A high resistance in that circuit could leave the ECU to think its connected, but unable to drive the valve. the fact it seems to be signing or humming would indicate it is being driven by a PWM output from the ECU as expected. you should see some voltage across the motor/solenoid pins in this case even with a multimeter.

If you still suspect the ECU, you might be able to get one from a breakers (with same VW part no) and just plug it in to quickly check if the valve is now operating from output tests. if it does, then depending on its exact type, you should be able to get the ECU cloned from the original. getting a main dealer replacement would be prohibitively expensive at this stage..

 

[Klaus Ludwig]

Thanks @stylers,

We have good continuity from all wires on the EGR valve plug back to the Engine ECU pins and no continuity to ground on any of them when measured on a multimeter Megohm scale.

According to the drawing, T6/3 on the EGR valve plug should be grounded and is not. We tried introducing a temporary ground at this point and this did not have any effect.

We know that 12v direct from a spare battery opens the EGR valve fully on a bench test. I have assumed that when carrying out a VCDS output test that the valve should open fully, however it barely moves. It must be getting some kind of PWM signal, but not enough. Need to confirm exactly what it is getting using a multimeter as we don’t have an oscilloscope.

Not sure if you have seen the video link I recently posted of our attempt at Basic Setting. Definitely was not as expected, though I have never carried out any kind of VCDS Basic Setting before.

Regarding your suggestion of carrying out a VCDS output test with an Engine ECU from a breakers yard; would we even be able to turn the ignition on (unless it came with a key) as our ignition key would not be coded to the ECU?

 

[Badea_Cristian]

I didn't read you full post but looking directly over you error i see malfunction on EGR (not an electrical issue).
This fault it's common to CBAx engine code resulting from broken EGR.
From my end i would see just 2 option:
-Replace EGR valve + Gas Colling Piece
-Remove it from Software

Thanks!

 

[Klaus Ludwig]

Hi @Badea_Cristian,
We have the same issue when testing with a new EGR valve and circumventing the EGR is not on our list of preferred solutions.

 

[Badea_Cristian]

then you need to check all wiring going to ecu..other possibility will be ecu itself to have an issue.

 

[Klaus Ludwig]

It is almost certain that our EGR valve problem is an ECU issue. VCDS Engine Group 123, field 4 went from 0.7V to 5.0V when the EGR valve was manually positioned at closed and full open respectively so feedback looks good. Pin to pin wiring integrity is good for all 5 wires connected to the EGR valve based on continuity tests and on multimeter checks to earth. The only anomaly found with this wiring was no ground at T6/3.
Now dispatching ECU to a second company for testing etc. Testing could not be completed by the first company (ECU Testing Ltd) for our particular ECU, though comm's and customer liaison were excellent. Watch this space...

 

[Robski]

The best test bed is the car itself.

Resistance/continuity testing wiring is about as much use as playing snooker with a piece of string.

 

[Klaus Ludwig]

Hi @Robski, I agree with you to a significant degree. To me, continuity testing is only an indicator. I prefer testing live and looking for volt drops where there shouldn't be any - wherever this is feasible.

 

[Uwe]

I prefer testing live and looking for volt drops where there shouldn't be any

Good.

Another useful technique is to load-test wires using a 12V bulb with a wattage appropriate to the circuit.

-Uwe-

 

[Klaus Ludwig]

Absolutely agree!!!

 

[Klaus Ludwig]

The second specialist company now has the ECU, Keys and Instrument Cluster. Should get some feedback from them this week...

 

[Klaus Ludwig]

Just received our Bosch EDC17CP14 ECU back from ACtronics. They did not find anything wrong, though apparently they did not load test the 12V output to the EGR valve as they “did not have a loom or EGR valve”
I’m not sure why they could not use alternatives.
Will continue with a few more tests whilst contemplating remaining options. Our ECU has now been to two ECU specialists…
On the official Bosch website they list all of their ECU’s and there are many. Each ECU has a list of typical failures and for our ECU (EDC17CP14) one potential fault on their relatively small list is “P0403 EGR Valve” - which is what we have.

Productdetails | Bosch

EDC17CP14,0281015029,Engine Control Unit,

www.bosch-repair-service.com

One assumption that I am making is that our EGR valve should fully open during a VCDS Output test. It does open, but only very slightly. Any advice/feedback on the latter appreciated.