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850 T5 ABS Woes

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

Cookeh
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Cookeh

850 T5 ABS Woes

Post by Cookeh » Mon Jan 28, 2019 4:40 am

Hi guys,

After lurking for almost a year (since buying my T5) and fixing almost all the issues with the car via your database I thought I'd make an account. I love my T5, even if it costs me a fortune in fuel doing 15k a year! I grew up in 740 Turbo and 940 Turbo estates so it was inevitable I'd end up in a 90s brick as my second car... would have been my first but insurance companies in the UK aren't too friendly to young adults in 2.3L cars...

Anyway, onto my issues. When I bought the car I had an ABS fault, it didn't work, didn't do its self-check whilst driving and I had the warning light on the dash. I did a lot of reading and replaced the ABS module with a refurbed one. This cured the warning light, but the ABS still doesn't work.

I found that the n/s ABS sensor cable had been rubbing on the old suspension (previous owner had fitted some dirt cheap coilovers that got replaced by me almost immediately, awful things) and you could see the core in two places. I ensured it wouldn't rub anymore by routing it correctly on the new suspension and used insulating tape and then a cable wrap to cover the core.

I still have no ABS, and still doesn't do the self-check but the ABS light is not on. Occasionally when turning from lock to lock in tight turns (parking lots) the ABS light would come on but it would reset itself by the next drive cycle. It hasn't done this for a few months now, however.

In terms of things I've checked, I've done the following in addition to the above:

- Removed and checked the re-manufactured module for dry solder or any issues in the joints
- Tried swapping back the old module (I had re-soldered this one myself) and still have the same issues
- Checked reluctor rings, they are fine
- Checked contacts on the module and cabling, no visible issues

Is there anything else that I can check or that is a likely culprit? I assume if one of the sensors themselves had gone or if the module was bad then that would trigger the warning light, but does the same apply to the ABS pump?

Many thanks in advance!
Cookeh



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abscate
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abscate

Re: 850 T5 ABS Woes

Post by abscate » Mon Jan 28, 2019 5:22 am

Try checking the torque on the axle nuts, a slight looseness here will cause ABS problems

The self test on ABS is automatic, how do you know it isn't occurring?

VIDA is the right tool to diagnose this, trying to guess component failure will be expensive and time consuming. My bet is you have codes which are stored but not triggering the ABS light which will guide you.


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Cookeh
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Re: 850 T5 ABS Woes

Post by Cookeh » Mon Jan 28, 2019 5:33 am

Thanks for the reply. I've checked it with VIDA not long ago and there are no codes. Same with a flash code reader on the ABS pin.

From what I've read regarding the self-check you can hear/feel the pedal pulsate when it reaches 25mph and checks the hydraulic operation?



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Sommerfeldt

Re: 850 T5 ABS Woes

Post by Sommerfeldt » Mon Jan 28, 2019 7:05 am

Relying on feeling/hearing that check is sketchy - it’s not always “rough” enough to notice. On my old t5-r it was very clear, while in my current it’s only intermittently noticeable.

As far as I know, ABS light is only canceled by a successful self-diag. Are you sure it’s not working...? :D

- S


'96 855 T5, R bumper and spoiler, Koni Yellows & blue H&R springs all 'round.

Cookeh
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Cookeh

Re: 850 T5 ABS Woes

Post by Cookeh » Mon Jan 28, 2019 7:18 am

Interesting, thanks. Fairly confident its not working - had a couple of 'moments' in the last year where I would have expected ABS to come on, as I could feel the wheels start to skid. Its rare that I have to resort to any braking that would trigger the ABS and if the light isn't on that's fine from MOT etc point of views, but would be nice to have it working!



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Clemens

Re: 850 T5 ABS Woes

Post by Clemens » Mon Jan 28, 2019 7:33 am

Try ABS the following way: Gravel road or parking lot or shoulder of the road; drive car in reverse. Step on brakes really hard. If no ABS action is hears or felt from the front tires, your ABS is not working.

Compared to modern cars the P80 cars have a quite slow responding ABS. I barely ever get mine to come on unless there is ice on the road.


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Cookeh
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Cookeh

Re: 850 T5 ABS Woes

Post by Cookeh » Thu Aug 15, 2019 7:52 am

Slight update to this, ABS light was out and stayed out until last week. Since then it is has been very intermittent, but when it does come on it does so during braking. Prior to the light illuminating in this scenario, you can hear what sounds like a vacuum pump and the ABS audibly kicking it (but only very faint pulsing in the pedal).

Once upon a time there was a code for the N/S/F wheel sensor, so is it possible that I have a dirty sensor/reluctor ring which is causing this intermittent fault? Or is it more probable that the issue is a faulty sensor/bad wiring?



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erikv11

Re: 850 T5 ABS Woes

Post by erikv11 » Thu Aug 15, 2019 9:16 am

Sounds like you didn't yet ohm out the sensor pathways? Instructions here https://www.midwest-abs.com
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Cookeh


'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 140k
'98 S70 NA, 210k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 280k
'06 S60 R, 160k
gone: '96 NA 850 210k, '98 NA V70 182k

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Cookeh

Re: 850 T5 ABS Woes

Post by Cookeh » Thu Aug 15, 2019 9:35 am

No, I haven't yet. Quick question regarding that, are the pins referred to (i.e. 11 & 4) on the wiring harness itself, and does it need to be unplugged from the module to do this? From the description, I am struggling to comprehend which these pins are, most likely due to my idiocy.



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erikv11
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erikv11

Re: 850 T5 ABS Woes

Post by erikv11 » Thu Aug 15, 2019 1:20 pm

It sounds like you've got the idea right: You test resistance on the harness connector, with the module unplugged.

So you actually probe the sockets (connector), not the pins (module). The sockets are numbered according to the module pin that plugs into the, So for 11 and 4, figure out the socket for pin 11 and the socket for pin 4, and test those two sockets with your multimeter. You're testing the circuit path from one socket down to the sensor and back up to the other socket.

Also, once you have those ohm numbers, a PM to member MattyMoo (runs midwest-abs) might get you some quick, expert feedback. Point him to this post.
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Cookeh


'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 140k
'98 S70 NA, 210k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 280k
'06 S60 R, 160k
gone: '96 NA 850 210k, '98 NA V70 182k

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