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

[Chris_Rogers]

While you're waiting for the meter I'd do the test I suggested in post 106.

[SkintKnuckles]

Hi Chris,

will do. Been pressganged into some Sunday afternoon events first.....

cheers
Neil

[outnumbered]

Take a breather and have some quality time with the family
Mike

[KBB]

As Chris mentioned it would be well worth double checking the VIDA Pin out signal description's for ECU Pins A:66, A:71 I'm content that A:28 is a ground circuit but only for the positioning sensing circuit since ground side control for the EGR pintle is through A:71 based on previous information kindly supplied.

The position feed back circuit is a little puzzling at the moment more so in its design. More commonly used is a 5v reference voltage, I was a touched surprised to see an open circuit voltage of 10.3v on pin 1 yellow wire at the EGR valve. This may be a "bias" line voltage often employed to increase self diagnostic capabilities in detecting opens and shorts in circuits. Although this is a unusually high voltage they run in the micro amp range as the come through an internal resistor in the ECU. Easy to prove if you take the normal open circuit voltage reading with a DVM and then using the screw driver automotive test light (which draw 250ma or less) with the fly lead and earth alligator clipped to ground touch it on the DVM positive probe whilst in contact with pin 1, if the DVM reading drops down to zero or very low its a bias line voltage.

I would be interested to see if any other owner gets the same open circuit voltage on pin 1.

[SkintKnuckles]

Hi all,

took Mike's advice and had a chilled out afternoon with the family. Did me the world of good. Nonetheless, I've took the opportunity to do a few sneaky measurements that I think are interesting, especially given KBB's post immediately above....

The measurements that i posted first thing this morning suggest (based on earlier measurements) that the car would be in high power mode when I drove it. It was. So far so good.

Went out for a drive to my sisters. The car was in high power for the first 16 miles. Then it went into limp mode. So I dived out the car and took some measurements at the EGR valve multiconnector (with the connector taken off, and using pin 6 as the earth, ignition at pos II):

Pin 1 (yellow) = 0.00V, pin 2 (green/white) =0.00 V, pin 3 (green/grey) = 10 mV.

These voltages did not change measurably when I used a chassis earth as the ground. Thus, when the car is in low power, it seems to definitely be the case that these voltages drop off, as per earlier. I'm not implying causation, but clear correlation.

After the car had been sitting at my sisters for a while, I went to do the test Chris recommended in post 106 (EGR valve multiconnector in situ, measure across pins 1 & 6 via back-pinning, energize EGR via pin 2 being earthed of chassis).

The results were : voltage between 1 and 6 = 3.04 V, between 1 and 2 = 9.8 V.

These results were independent of using a chassis or battery earth. As with earlier measurements, earthing pin 2 off the chassis/battery earth did result in EGR actuator being energised, but zero detectable change in voltage.

Just as a reference point, I did the same measurements with the EGR multiconnector off, and obviously I couldn't energise the EGR valve with the connector off. Interestingly, given KBB's recent post above, the voltages were:

Between 1 and 6 = 11.01 V, between 2 and 6 = 3.29 V.

Before anyone asks, I am absolutely certain that I measured the right pins and recorded the right voltages. Why? I measured them multiple times and then asked my brother in law to do the same - he got the same results.

Why do I report this here? Well it seems that the voltages between 1 & 6 and 2 & 6 invert when the connector is on vs off the EGR valve multiconnector. In concert with this inversion, there was a very clear reaction/powering up of components happening inside either the EGR valve or the EGR position sensor when the connector was pushed back on (ignition on pos II).

KBB - does this inversion of the voltages now make sense, but only when the multiconnector is in situ. To me it seems that the open circuit voltages for the pins (ie connector disconnected from EGR valve assembly) don't make sense, as per your post, whereas they seem to make sense only when the connector is in situ.

Any ideas folks? Wow - this is a mystical problem....

cheers
Neil

[SkintKnuckles]

Hi KBB,

early in this story, on a different thread, Mike (Outnumbered) saw similar open circuit voltages to me (i.e. his fully functional D5 vs my D5 in high power mode):

"at the Egr position sensor multi plug with ignition on position 2
Green 12.7 v
Green/White 3.30 v
Yellow 12.27 v
Brown 0.01 v
the above is what i get on mine
hope that helps
mike"

Similarly, I measured the same values as my own on another board member's 185 bhp D5 V70 (don't have them to hand, but basically the same as Mike and I's values for each pin).

Thus, when my car is in high power mode, it does indeed seem to have the stereotypical open circuit values for each pin (earthed off the engine bay in the other guys cars).

It'd be very interesting to see if other people see the same inversion of voltages between Pin1 and Pin2 that I see (with the multiconnector in situ, connected to the EGR valve and back-pinned to measure voltages against Pin6). If not, its peculiar to my car. Any takers.....

cheers
Neil

[Chris_Rogers]

"After the car had been sitting at my sisters for a while, I went to do the test Chris recommended in post 106 (EGR valve multiconnector in situ, measure across pins 1 & 6 via back-pinning, energize EGR via pin 2 being earthed of chassis).

The results were : voltage between 1 and 6 = 3.04 V, between 1 and 2 = 9.8 V. "

What was the voltage between 1 & 6 before you earthed pin 2?

"measurements at the EGR valve multiconnector (with the connector taken off, and using pin 6 as the earth, ignition at pos II):

Pin 1 (yellow) = 0.00V, pin 2 (green/white) =0.00 V, pin 3 (green/grey) = 10 mV."


Pin 3 @ 10mV is suspect as this battery supply is via relay FMA3 and fuse 11B/15.
Note that relay FMA3 is the main system relay, if this had de-energised the engine would stop.


I think I'd look at fuse 11B/15 for a poor connection and then with a voltmeter on EGR connector Pin 3, do a wiggle test on the wiring to look for an intermittent open circuit.

[SkintKnuckles]

Hi Chris,

thanks for the feedback. I'll definitely look at this fuse next. I'd love it to be as simple as this (in terms of a fix, not finding a fix). Weather permitting, I'm aiming to do all outstanding tests tomorrow.

Re: your question "What was the voltage between 1 & 6 before you earthed pin 2?"

The voltages I reported were the steady state voltages between pins 1 and 6 (i.e. no energising of the EGR valve via pin2) using back pins and with the connector attached to the EGR valve assembly. Apologies for any confusion in my text.

The measured voltage between Pin1 and pin 6 did not change upon energising the EGR. Thus, in my hands (which is perhaps a caveat), even though I can energise the EGR valve, this doesn't cause a concomitant drop in voltage at Pin 1.

Earlier tests recommended by KBB also gave the same result for Pin 3 (i.e. no change in voltage at Pin3 during energising of the EGR valve).

cheers
Neil

[KBB]

As Chris suggested with the EGR connector in place and DVM back probing flex the harness gently to see if the missing voltages come on line, the is a spliced joint in the harness 53/335.

Also with a heavy-ish screw driver tap the area of the EGR drive section with the handle and see if voltages come back on line and a blast of the EGR body with carb or brake cleaner that has a very low temp just to induce cooling to see if cooling brings this on line.

Could well be an internal thermal short pulling the voltages down.

[Chris_Rogers]

You may find it useful to connect a 12V lamp between EGR connector pin 3 and chassis earth, with the EGR disconnected.
The 11B/15 fuse rating is 15A I think anything up to around 21W would be OK but have a look at the conductor size to confirm.

This will load the circuit and make any break easier to detect as you wiggle the wiring, i.e. the lamp will go out.

I'd also check the voltage at the other components supplied from the GN/GR wire, this may help to narrow the fault down, connector 54/1B maybe a good place to start.

Some pages you may find useful in TP3989202, 57, 176, 207, 219, 222.