Engine: D5: A puzzle for the EGR valve expert/masochists out there...

[SkintKnuckles]

Hi 4c,

£15 is a bargain. I too hate the electrical angle, but I think its got to be back on the table now as the fault is so intermittent and random that a loose/dodgy connection could explain it. To date, I've contact cleaned all connectors that seem related, but no fix yet.

cheers
Neil

[SkintKnuckles]

Hi mate,

just saw you PM re: use of your volvo software/ real time diagnostics. I'd love to do this, and thanks for the kind offer.

I'll email you in the next day or so to see if/when you can be free for this and I'll come to you whenever suits. Thanks so much. It'll be great to see the underlying sensor data in real time, as opposed to the resultant DTC codes

cheers
Neil

[4candles]

I think the code flagged may be spurious, sometimes a Non Volvo specific reader, rather than keep schtum when it doesn't know will spout some generic bs to appear its doing its job,

Someone mentioned the famous four, or five things that cause the limp mode,
maybe you just got to work through that, or PM someone like 'clan' directly rather than waiting to see if he pops in...

[SkintKnuckles]

Hi all,

well today has thrown up a few new insights on the old 44B0 error and EGR valve shenanigans. I'll pop them below and would greatly value anyones opinions on this and my amateur diagnosis. Thanks to Mike (outnumbered) and Kenny37 for help with the electrics and VIDA analysis!!

Ok, I did quite a few voltage readings, as per Mike's suggestion, at the connector for the EGR position sensor. The long and short of these is that there is no voltage in 3 wires (of 4) when there really should be. I re-checked this on different sensitivity ranges and using different earths and got this answer repeatedly. Conclusion - for whatever reason, the electrics to the EGR position sensor appear dodgy - at least at the time tested.

Next, I did some work with the help of Kenny who had the cool Volvo software. We did the usual code clearing/reading/clear adaptations etc. The results were fairly clear (I have photos but they are currently stuck on my phone). The gold ol 44B0 code is still here (EGR position sensor faulty signal). However, it brought along a new friend, 4430 (EGR valve signal missing). Conclusion - the brand new EGR position sensor, which I assume works well, aint working for one reason or another. However, if it isn't getting the juice from upstream (as per the leccy test) then you wouldn't expect it to work.

Next Kenny and I looked at some real time data. The take home message was that: The EGR position sensor basically flatlined at between 0.7-1.0%. I guess this is no change at all, in terms of how accurate the measurement is. However, the EGR valve stayed at 100% throughout. Ok, there were a few minor blips to 40% but these were fleeting and I'm not sure they weren't noise. Then Kenny did a manual drive of the EGR valve using his cool software. This repeatedly gave rise to a noise that lasted for 2-3 seconds and came from the EGr housing, but no change in valve position. This suggests the electric motor is working on the EGR valve, or at least responds to requests for movement.

Ok, to date, I've always assumed that there had to be a rational explanation for why my car oscillated from low to high power in an almost random manner. If I've got an intermittent short or an open circuit in the loom upstream of the EGR position sensor, then my guess is that this can allow the EGR position sensor and EGR valve to work properly when the circuit is closed, but then to loose this (inducing limp mode) when its open/shorting. Do you guys agree with this or do you see a more mechanical origin?

If this is an electrical open/short circuit, I imagine this may not be so easy to tie down. Even if it is, it feels a little daunting for me! Any ideas what the best/most cost effective way to move this forward, if indeed the above is right? I'm well outside my comfort zone, being used to spannering multi cylinder petrol motorcycles

Any feedback, as always, much appreciated.

cheers


p.s. I forgot to say. Both before and after the above electrical tests and VIDA stuff were made, the car was most definitely in limp mode. So, it seems safe to say these measurements map to the broken state of the high-low power cycle its constantly switching between.

[Symes]

Sounds like you might well have found the culprit!

Next thing is to get the wiring diagram and see where the signals are coming from, most likely the ECU on the top of the air filter box... the ECU has to be removed to change the air filter(!) So its possible that the connector contacts might need a clean or even have been bent or broken.

At least when you have the wiring diagram you can do a continuity test and rule in/ out a break or short in the cables.

I think this thread demonstrates (again) the power of the Forum; people willing to offering advice, their own experiences, equipment and time in order to help each other out.

[SkintKnuckles]

Hi Symes,

I agree! I had a look at my Haynes manual for this model, and it didn't have this circuit in it. Any ideas where may be a productive route for finding this information.

For what its worth, when I did the clean up of the EGR etc, and the battery was disconnected, I did a clean up of all terminals at the EGR side of things. However, at that time, I wasn't really expecting an electrical issue, altough it was at the back of mind (where I was avoiding it!).

What is weird in all of this is that, if this is a short etc, then 3 wires seem to have gone in concert. If this is indeed the case, my hope is that this is easy to spot (i.e. a slice/dent in the wires). Equally, the damage shouldn't be too great as the car oscillates between full power and limp mode during driving, so it 'fixes' itself.

I couldn't agree more about the forum. so many people have been so helpful, and so generous with their time and experience, that its been a real breath of fresh air. On a personal level, its made me dig deep into areas that I'm not really comfortable with, so this can only increase my skill set -albeit at the expense of my mood and life expectancy

If the above diagnosis right, I'm kind of annoyed that the Volvo specialist didnt find this, especially given the information that Mike sent me, which was one of the key checks in the Volvo software.

cheers
Neil

[SkintKnuckles]

Hi folks,

Eureka!! Ok, the car is not fixed, but the earlier diagnosis (i.e. short or open circuit in wires to EGR position sensor) is sound. On the suggestion of Mike, I inserted a sewing pin into the rear of EGR pos sensor block connector (at the sole wire where I was getting a weedy voltage from). I did this so that I could get a voltage reading when the car was in limp mode and in high power mode with the block connector in situ.

The results..... In limp mode, the voltage at the 'pin' wire was 26-30 mV (whereas Mike's value was ~12.5). Went for a drive, the car flipped back into full power mode. I jumped out the car, and did a quick reading with a multi-meter. The pin now gave 12.8 V. Thus, the voltage to the EGR position sensor varied by 1000-fold. To my mind, this is definitive proof of the flaky circuitry for the EGR position sensor being the root of all my evils as low voltages in EGR pos sensor give limp mode, whereas the correct voltage gives full power. THe relief that things are making sense now!!

So far, so good. However, without a circuit diagram for the wires running from the EGR position sensor to the ECM, its going to be hard to nail down. I'll start a new thread to see if someone has this. If I can find where the break is, I'm sure this can be fixed. I couldn't find anything obvious, but thats mainly down to the loom being so complex.

cheers
Neil

[SkintKnuckles]

Hi guys,

I just wanted to throw a few other pieces of information into the mix for all you salty ol' dogs of volvo mechanics to chew upon. I'd completely forgotten it, amist all the brain overload and recent elation with the short/open circuit being confirmed.

Ok, when I did the VIDA check with Kenny37 the other day, something we noticed was that the throttle read consistently at 91% and didn't move during repeated tests. However, in the real world, the car started and idled beautifully, revved on demand etc and generally worked perfectly. Similarly, there were, and have never been any throttle/ETM related error codes.

Do you guys think this is a false reading? I kind of wrote it off to this. I cannot understand why the throttle appears to be working perfectly, with no DTC codes, yet this is a drive by wire car, so if the electronics think the throttle isn't moving then it shouldn't move, no?

Thus, I wanted to scope you out on this. Maybe if the throttle is perceived to be 'fixed' at a given level then this, in turn, could 'lock' the EGR position sensor i.e. the low voltage I'm seeing (whicch gives limp mode). I'm open to the possibility that this could be down to the ETM (which has a mere 25 K miles on it).

The other thing thats weird, and may be a red herring, or contributory, is that I've absolutely failed to get an earth from any one of the fixed earthing points in the car's engine bay. To get a useable earth, I ended up running a wire from the negative terminal at the battery. Maybe this too could be the cause of the high/low voltages?? That said, no other component in the car appears flaky, and many of them are earthed off the engine bay.

To date, I've assumed that the VIDA readings for the throttle were wrong (for whatever reason) and that I'm a crap sparky (hence the inability to find an earth) Thus, I'd appreciate any and all thoughts!

cheers
Neil

p.s. Kenny37 checked his VIDA on his d5 V70 and it showed 'moving' values for the eTM, EGR valve and position sensor when the throttle is blipped, hence my values seem real, if not reflected in the reality of the throttle response.

[4candles]

What a head fcuk dude, glad its not my problem,

With no wish to send you off on a wild goose chase, in my mind the EGR and its posistion sensor must be controlled via the ECM in the engine bay, and i believe it controls the switched earths to said components,

As the great Chubby Brown once iterated, " I'm no gynocologist, but I'd have a fook'n good look, lol"

Hope you get that wiring diagram, in particular i'd be looking for what ECM pin numbers are relevant, and will help re. continuity checks of loom..

Where you have no power at plug, i presume you checked said wire for the elusive volts back a little bit on loom at least to eliminate a connector issue?

4c.

[Jetmech]

Ok a little knowledge is dangerous and I have little knowledge of things electrical! But I think this is the correct wiring diagram item 8/120 is the egr valve. It looks as if 4candles is correct, the ecm does the controlling. Anyway I hope this helps.
wire diagram.jpg

The screen shot isn't very clear, from the top. The yellow wire goes to pin A66 of the ECM plug, green/white pin A71, green/grey doesn't go to the ecm, brown/black pin A28.