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164 Q4 ABS problem (warning light on)

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Re: 164 Q4 ABS problem (warning light on)

Postby Alfan » Sun Feb 18, 2018 8:05 pm

I went for a short test drive in the Q4 yesterday and the ABS error code reappears after being erased. I will probably try and put the other unit back in later, to see what that will bring.

I took photos of the error codes from the Marelli tester.

2018-02-17 15.17.57.jpg
ABS error 1

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ABS error 2

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ABS error 3

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ABS error 4

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ABS error 5
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfamuppet » Tue Feb 27, 2018 4:02 pm

Looks like the front right and rear left solenoid valves have a problem ? These would be part of the ABS unit probably controlled by relays
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfan » Mon Mar 05, 2018 3:58 pm

As mentioned earlier, I have had the welded relays replaced - before that it gave *pump motor' failure. I think this is a problem within the mechanical unit, so I will try and replace that with another one and see what comes out of that.
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Sun Sep 02, 2018 6:36 pm

Long time has passed but I will be posting an extensive update on the thread very soon.

I did a lot of measurements which will be helpful for everyone here (for example I've mapped all components from the schematics to the actual physical unit, so I know what is where exactly and how to measure it from the top).

At this point I'm pretty sure that my pump motor is shorted to ground thus causing issues on both relays, but I will ask you guys for your analysis here as well, so stay put, I'll post the details soon. :wink:
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Fri Sep 07, 2018 12:32 pm

So here are the mappings I've done between the N51 group and schematic. You can see which diode is where in reality, diode labeled by me as 4 and 7 are not visible. There is also my crude hand drawing, where you actually can see what is connected to what, I will try to digitize it when I have time. :)

q4_abs_onepage_diagram_annotations.jpg

q4_abs_group_n51_relays_photo_annotations.jpg

q4_abs_group_n51_hand_drawing.jpg


Hopefully this is helpful to everyone.

I'll be posting my measurements soon, as something does not add up in my case unfortunately. :mrgreen:
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Fri Sep 07, 2018 1:09 pm

Results:
- I am measuring ground when the screw leading power to the pump motor is screwed down (this I suppose is short to ground, it's not supposed to be shorted, but I may be wrong)
- Because of this the measurements are split into 2: with the screw in place (would be normal operation, but I fear it's shorting to ground), and without the pump motor connected at all (no screw in place)
- After 10 or 15 seconds the solenoid valve relay disengages on it's own, I assume N51 group CPU is ordering it to shut off, this is measured as +10,8V on both pins 85 and 86
- I've marked in orange what I think is wrong on the measurements
- Battery voltage is measured at ca. 11.2V, drop to 10.8V on relays may be due to loss on the diodes
- I don't understand why the voltage on pin 87, 30 and 86 (as they are all connected) drops from ca. 10,8V to 0,7V when the relay is engaged (this is only on key ON)
- I don't understand why pin 30 of pump relay is getting 10,6V after 10-15 seconds when solenoid valve relay disengages, it should get it's current through pin 30 of said relay
- Even with the pump motor (and potential short to ground) disconnected, I don't understand why voltage on pin 87, 30 and 86 drops to 0,7V as it's taken directly from the battery via pin 87

results.JPG


Will be extremely grateful if anyone more experienced in electric circuits could help out here and diagnose why am I seeing what I am seeing here.

Many many thanks. :oops:
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Wed Sep 12, 2018 2:06 pm

I was not expecting to say this, but... I FIXED IT :!: :!: :!: :!: :!:

Finally, after many years my ABS light is going off after initial checkup! I could not believe it when it first worked. :D

The diagnosis turned out to be somewhat misleading. What was ultimately the culprit was relatively straightforward: bad connection on the G416 60A main supply fuse for the ABS. :!:

Image

What was misleading, was:
a) Diagnosis reporting error as "faulty solenoid valve relay" which was indeed not the case, but after one understands how this is verified (looking at the diagram you can see where the ECU takes it's inputs from)
b) No G416 fuse on the main ABS schematic, it's only included in the "hot wiring" section of the manuals
c) Loss of voltage only after the relay has been engaged

But nevertheless, it was suggested to me that I should check the supply voltage on pin 2 of G272 and go upstream from there, checking if it reads reduced voltage all the way. I had a look at the schematics to see where this wire leads to and ultimately found the "hot wiring" diagram, where G416 is mentioned.

The fuse (at least in Q4) is located right on the firewall, next to the coolant reservoir and next to the G56 junction (sort of screwed in and sticking out to the side of it). The two connectors holding the 60A fuse were completely covered in oxidation...

Cleaned it up and presto, ABS light goes off, voltage measures as it should everywhere!

ABS - solved. For the first time I have no warning lights on my dashboard! :mrgreen:

20180912_145427.jpg

20180912_145436.jpg

20180912_145452.jpg

20180912_141530.jpg
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfan » Thu Sep 13, 2018 9:59 am

Awesome!!! :D :D :D

I need to investigate this on my Q4, when I get time to start working on it again. Hopefully, it will have the same impact...
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 ABS problem (warning light on)

Postby alfa east » Thu Sep 13, 2018 12:01 pm

Wow, we all rejoice because you were on to this for quite a while!
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Thu Sep 13, 2018 1:56 pm

It's tears of joy let me tell you. :D

I've just been testing the system with my Marelli tester, ran the pump motor test and the solenoid valve actuation test a couple of times to flush the old fluid out, and the system is blocking and releasing the wheels and pulsing as it should. Very satisfying :!: :)

Fingers crossed that you can sort out your issues as well, the main fuse should definitely be the first on the list.
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfamuppet » Fri Sep 14, 2018 8:43 pm

Great news and it’s brilliant when the fix is that simple!
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfan » Sun Sep 23, 2018 5:41 pm

So I finally got to drive the Q4 and having only replaced the 60A fuse (and only driving outside the garage), the ABS light did not come on!!!

So I have hopefully confirmed your observations :mrgreen:

I did not care much that the engine started to stutter when parking it, as I think it is low on fuel, though...

So thanks a lot for finding this very simple solution :D :D :D

Now I should only have a few other things to fix :wink:
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 ABS problem (warning light on)

Postby AlfaWhiz » Tue Sep 25, 2018 10:25 am

Wow, that's wonderful news! :D

Looks like the ABS unit itself proves to be quite reliable, and Alfa engineers should have included this simple step in the debugging instructions too! Would save everyone a LOT of trouble. :mrgreen:

Thinking about it in retrospective, this fuse looks like a total afterthought. Literally every single other fuse is located in some predesignated place, while this one is stuck on the firewall without any cover.

But it's good at lest that we have a simple fix for this apparently complex problem, hopefully we will only need to tend to the fuse again in about 25 years from now. :mrgreen:
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Re: 164 Q4 ABS problem (warning light on)

Postby Alfan » Tue Oct 02, 2018 9:24 pm

Yes, the location of it does not look very integrated. Another small test run this weekend was fine, no ABS light coming on unexpected - and putting in some fuel made the car run smoother again :)

It was on display at the 'open garage' as well, together with another project - not mine!
20180930_150944.jpg
Alfa on show
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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