Did I make a big mistake with ABS on my '92 240?
I need help! When I got the car five years ago the "Check ABS" light was on all the time. So I disconnected it by pulling out the relay. As I recall it drove and braked okay. It gave me some time to use the car, and locate new reluctors, which I bought from a guy in England. I also had to fabricate new dust shields by modifying some for a 240 without ABS. (Not really so hard to do, cut a hole for the sensor wire to pass through, and cut away some of the sheet-metal to fit around the caliper). I also had to replace front bushings and one front control arm which was lost to rust. This was a Connecticut car - lots of road salt! At that time as I recall I replaced all four calipers and pads, maybe rotors also. That was 2017.
I cleaned everything up and installed two new front reluctors and both sensors. When I reconnected the relay the "Check ABS" light came on and stayed on again.
I had cleaned a lot of corrosion, rust and wheel bearing grease off both front hubs. The reluctors were so corroded I had to cut them off.
The "Check ABS" light stayed lit on the instrument panel. So I once again disconnected the ABS relay.
After annually changing the right front caliper, and less frequently the left front caliper in September 2023 the car was braking on both LF and RF. After a few miles of driving both sides were very hot. Rear brakes not.
In January 2023 I completed replacing all four calipers and rotors and pads. I bled the whole system very thoroughly with a pressure -assisted pump to the master cylinder reservoir. I read through all the FAQs on the Brick Board. I got a hint to check the junction valve up by the front left wheel well. I've cleaned it extensively but I have not been able to crack it open with a Allen wrench to let trapped air out. I don't know if air is trapped in there. I have bled it thoroughly again at all four wheels in the proper order for an ABS system. This time the rear rotors were showing barely any wear and contact with the new brake pads. But both front rotors were heating up and smoking after I went a few miles. I was still driving with the ABS relay disconnected.
I read about the rubber brake lines possibly being worn out and too soft and generating pressure within the system which could force the calipers to move. Now I have bought a new set of stainless steel woven protected rubber brake lines, one for each front wheel, and one for attaching in the brake line just above the differential which then splits to steel lines to each rear wheel. I haven't replaced the three rubber hoses yet because I wanted to ask here on the brick board for advice.
I'm wondering what my next step should be? I can start by bleeding the whole system again to make sure there is no air in it.
But am I creating a problem by keeping the ABS system disconnected/nonfunctional? Can the brakes still function without the ABS computer control? If that is an absolute yes requirement I will get onto that the very next thing. I imagine it will be a thorough going over/cleaning of the reluctor's and checking the gap on the sensors to the reluctors. I will check all the wiring up to the ABS controller, and also make sure I have power to the ABS controller.
Any special procedures or hints, or what to look for or what to do?
I greatly appreciate any help. I love driving his car and it's in good shape. I need to use it as a daily driver. TIA.

Last night I discovered I have a steady drip around the rubber washer between the brake fluid reservoir and the master cylinder. I put two guys around it, squeezing it with much more even compression onto its seat. I went back out this afternoon and found out it is still weeping brake fluid.
That was while I had the power bleeder pumped up to 20 psi.
As I've said I have bled all four wheels in the proper order for an ABS system two times and am getting clear brake fluid coming out. There are no other leaks in the system, lines and calipers. No leaks at the ABS distribution box, nor the junction box on the sheet metal driver side accessible from underneath. I cleaned and dried it. It stays dry.
So that's where I am now I'm going to look up that washer, or gasket whatever it's called. Seems like that's the next thing I have to fix. Then go back to bleeding the system again.
Now I'm going to read all the posts that you guys have all put up as help.

I called my local Volvo dealer and they do not have the grommet or gasket, which Volvo calls a sleeve, part number 1221713. He said NLA. I just ordered four of them from IPD, aftermarket, at $1.95 each.

there's an over voltage protection relay for the ecu. on the pass side, under the dash. look for a relay with a 10amp fuse in it. it's possible the fuse blew but on mercedes i change that relay every 10 years as they don't age very well and just replacing the fuse doesn't fix it. it's job is to prevent voltage spikes or excess voltage reaching the ecu.

Thanks, I will check all of that. You're helping me learn more and more.

i haven't owned a car new enough to have ever worked on ABS. I had to look up "reluctor", at first I thought it might be the same as a "flux capacitor" ;-)

all I could add is that if it has that device in the brake lines with a piston it's used to shut off a leaky circuit and allow pressure to what's left.. That thing has a piston that moves and a wire that senses the position of the piston. the right bleeding sequence procedure can reset it to the middle where it lives, I'm sure it can be checked electrically.

If it has that, it might be pertinent to follow the right bleeding sequence to reset it but that may not even exist on your car. I think on previous models, if you happened to have a hose off and pressed the brake by accident it may shift the spool in that thing and cause a warning light but this is not really related to the ABS.

otherwise you are getting better advice than I can offer..

Good advice also. I have read and evidently frequently asked questions and the 900 series factory service manual, and heard much information here on the brick board that I know what you're talking about. I'm forgetting the name of that pressure regulator/separator also. I cleaned the one on my car and dried it well. It has no leaks when under pressure. I do not see any electrical connection to it for some kind of a sensor.
I have read in several places of the piston getting stuck in one of its functional distribution positions and causing a problem which sounds like mine. The last time I took it out there is very little if any braking force only to rear wheels, and the two front wheels were very hot and overheated starting to smoke.
Having just discovered that I have a leak around the gasket seal between the brake fluid reservoir and the master cylinder, I am suspicious that some air may be getting in there, causing my problem.

Unfortunately yours is a pre-1992 240 ABS system that doesn't use the OBD system to store diagnostic codes that would help pinpoint the reason the ABS warning light is on.

You did of course clear the original ABS fault(s) by disconnecting the battery?

Check the front ABS sensor tips for any signs of damage (chipped edges). Also check the front sensor cables and connectors for signs of damage (open up, clean and reseat the connectors). The reluctor teeth need to be mildly clean and the gap to the sensor tip has to be approximately correct. I imagine you're well past all that by now.

The ABS warning light is not associated with hydraulic system issues, but rather ABS sensor and control module issues, so basically electrical. Apart from the physically obvious, there are voltage tests you can do to see if things like grounds, control module connections and that relay are okay. The relay is certainly a suspect area once you verify external damage. I see mention elsewhere of a fuse at or in the control module (up behind the glovebox in your year, later year 1992-on under the front passenger seat) that gives an ABS fault when it blows, but that was discussing a '92 240.

Refer to the ABS section of the 700/900 FAQ here for tips and procedures https://www.brickboard.com/FAQ/700-900/BrakesABS.htm. Your 1990 240 system should be very similar (if not identical) to the early non-OBD 700/900 ABS systems described in the FAQ.

An early 1990s brake service manual and full proper wiring diagrams would be useful (preferably 240, even 700 would do), but may be difficult to find online. A quick look for a suitable bootleg manual didn't turn up anything. Apparently Bentley has not too bad a section on ABS.

Hope some of the above at least helps you get to the next level on this. Many of us have had minimal issues with our ABS systems beyond keeping things clean and inspecting for damage.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Thanks very much Dave for all that good information you gave me. I'm going to go through it all from top to bottom.
My car is a 1992 245, with ABS. You seem to have picked up somewhere that it is a 1990, which is I think pre-ABS.
I read some of your other posts as I searched through related threads on 240 brakes. Those have been also very helpful for adding to my knowledge. I often save and print out a helpful answer so I can take it out to the car with me.
I'll let you know how it goes by posting back here.

Hopefully I can clear up some confusion on 240 ABS - maybe... or maybe add to it...:)

91 was the first year 240's had ABS. Yes, I believe it was a midyear option. It was standard on 92 and 93's. All 240's were OBD1. Meaning all the socket holes dedicated to ABS were empty as Dave mentioned. OBD2 is required to get ABS trouble codes. As you noted, if the ABS light is on it is usually due to grime or rust on the sensors.

As suggested, check your ABS wiring and grounds. Perhaps it is something simple like that?

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Will I buy another Volvo??? We'll see....

Hi JW,

Some good info on the 240 changeover years for ABS. Starting in 1989, the 240s and 700s got the newly mandated OBD (OBD-I) system in North America with the underhood diagnostic connector, a single connector then. Any models that got ABS had the early version of the controller that did not have OBD capabilities. Only select models and trim levels got ABS initially, such as the North America market '89 740 GLE (which I had). Volvo updated their ABS controllers to have OBD (OBD-I) capabilities starting in 1992 as the changeover year. If it was a calendar year mandate then that would explain a mid-1992 240 model year change you mention. I'm unsure of the 700 changeover years, but I suspect it's the same, carrying on until the last models were off the line in 1991. For the 900s, as a brand new series, they may have changed over earlier in 1991 with the introductory 940 SE (quasi 960 turbo) and GLE (16-valve) models, or they may have waited until the main 940/960 models started coming off the line for 1992. My reading elsewhere says the (later) '92 & '93 240 models did have ABS OBD on the diagnostic connector (port #3).

Contrary to what you seem to suggest, the underhood diagnostic connector with OBD-I fuel ECU, ignition, SRS, ABS, and power seat diagnostics continued in the subsequent 940 series right through until 1995, when OBD-II was mandated in North America starting with the 1996 model year. It was in 1996 that the underhood diagnostic connector was changed to the now required universal OBD-II socket in the console where an OBD-II reader was now needed to figure out what was going on and perform additional diagnostic tests and settings. ABS OBD continued on port #2 until 1995, then being integrated into the OBD-II diagnostic socket.

As noted elsewhere and in the FAQ, beyond basic issues at the sensors and their connector cables, the early surge protector (located next to the controller and not used in the later years) was a known problem area, especially the 10 amp fuse.

As I side note, on connector port #2 for the fuel side ECU, not only can you read out and reset diagnostic codes, there are also diagnostic tests you can perform, such as checking switches and sensors and operating devices, like rocking the IAC, operating the fan and pulsing the injectors (all described in the OBD FAQ section). What's not mentioned in the FAQ, and I'm almost certain I once saw it somewhere, is that you can perform similar diagnostic functions on port #3 for the ABS. One test I recall was pulsing the solenoids in the ABS module, which not only proved they could operate, but was useful for bleeding the brake lines through the ABS unit. I can't find that procedure in my manuals or a quick google search, so I may have been incorrect or it was for a different car. If someone can find a reference for that or any other ABS tests you can perform at the diagnostic connector, perhaps they could note it in a reply here.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

I stand corrected about OBD1 not having the capability to throw ABS trouble codes. I was misinformed. Should have done my own research on it and not listened to someone else! Also, probably got a little confused by my 90 240 with no ABS (which I owned for 11 years) and its OBD1 set up. Think the memory of that car's OBD with empty ABS ports stuck in my brain! Incidentally, I had 93 and 95 850's with the same, later model OBD1 and never had an ABS issue with either one.

Jim
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Will I buy another Volvo??? We'll see....

Jim, actually you were correct. There's no use of the "ABS port" on the OBD-1 box in a 240. That's a thing Dave knows because he owns 940s, where the port is used.

I know this from experience, but can back it up with documentation.





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Art Benstein near Baltimore

Generally speaking, you aren't learning much when your lips are moving.

Hi Art, hope you're not getting too sensitive about us 700/900 types posting in the 240 forum. The last 240 I was intimate with was LH2.4 in a 1989 245, bought new and still in the family, also having my 1989 740 at that same time for direct comparison. There's a lack of online documentation for the later 240 years, especially wiring diagrams, also the number of experts here other than you, so you have to forgive for me extrapolating the final 240 years into the 700/900 series I'm now most familiar with.

I often make comment here when posting about 240s of how things are the same or different in the 700/900 series as a number of people here have both series or graduate into the 700/900 series hoping that things haven't changed from what they knew and love. There are so many systems and problems shared between these model series. You should consider posting in the 700 forum more often as your knowledge and experience would be of great benefit there and as I recall there is a later 740 in your family.

As you know, I have the highest regard for your 240 and general knowledge, so anytime you're able to reply here soon enough for the OP then I try to back off and sit back to learn from you. I'm a bit jealous of your 92-93 240 electrical manual. Is that hidden somewhere online, I forget?
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

I am seeing how much more complex this is or could be then I knew. I may have to reread all these posts, print them and then circle all
the important things I have to do.
Thanks again for your depth of knowledge and for sharing it.

Sorry I got the year wrong. When replying, I wasn't looking closely at your post title, but rather at the post model/year fields where you indicated ALL years and somehow remembering a 1990 240 thread I had just been reading.

As I noted, that means your 240 should have ABS OBD, although it's possible your 1992 was like the 1991s without ABS OBD. You can tell by looking at the diagnostic connector under the hood. Look down into port 3 of the A connector block. If it's vacant (you can see right through) then no ABS OBD, otherwise there will be a female connector in there to use to access the ABS controller. The standard procedure is in the 700/900 FAQ here
https://www.brickboard.com/FAQ/700-900/BrakesABS.htm#ABSDiagnosticCodeRetrieval

If the ABS warning indicator is lit then there will be up to three trouble codes stored. The code(s) will point you to the problem sensor(s) or things like the brake pedal switch or the control module itself. Note that if the code points to the brake pedal switch, the signal may come off the bulb out sensor relay connector rather than directly from the brake switch, in case you've done any wire butchering there to bypass the bulb out relay.

Please post back with your progress and eventual diagnosis.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Just a short note to clear up the 240 ABS offerings: In the 1991 year ABS was an option, not dependent on date of production. In '92 and '93, ABS was standard.

The only electrical difference I can find between the version in '91 and the standard 92-93 is there's an outboard pulse prescaler (divide by 4 counter) to convert the pulses from the 48-tooth tone ring in the ABS car's differential to match the speedometers used in '91, which were functional for 12-tooth rings. All other wiring is identical, except the ABS electronics got moved from the firewall to under the front right chair. In 92-93 cars the speedometers had this prescaler built in.
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Art Benstein near Baltimore

Expert: An "ex" is a has-been and a "spurt" is a little drip under pressure.

Hi Art, so what you're saying is that 240 series ABS never got OBD-I capability and thus never used port #3 on the diagnostic connector. I certainly knew that was true up until at least 1991, as in my posts elsewhere here. The 700 series started out the exact same way in 1989 when ABS was first offered on select models, exact same system, no OBD-I. Both systems used the transient surge protector (aka. spike eliminator), which was clipped under the passenger seat near the ABS controller in later 240 models (in 700/900 models these lived under the dash on the driver side). The Volvo wiring diagram for the 92-93 240 that you kindly provided in your other post in this thread clearly indicates that (see also below). Some of the posts I've seen here and in other 240 forums were incorrect or misleading about changes and OBD-I capability. ABS systems didn't change for 240s until 1992 where basically just the controller moved under the passenger seat. Based on other posts, that may or may not have been a mid-model year change. When North American 240 assembly production moved from Halifax back to European plants for 1992 as the model series drew to a close then that might lend credence to what people find in their 1992 cars.

Looking more closely at the wiring diagrams you provided for the early ABS system (matches my 1989 740 manual that uses the same controller as you'll see below), the ABS warning light on the dash was raised off a ground provided by pin 29 of the ABS control module or various subtle faults to ground through the ABS unit or through pin 32 on the ABS controller (which sees missing or faulty signals from the sensors). There would be no diagnostic code to figure out the fault. You had to resort to fault tracing with a meter, as is indicated in the service manuals. My hopes for the OP being able to easily diagnose the errant sensor are now lost.

On further investigation using the North American Volvo dealer parts chain listings, the early ABS control module p/n 3523142, without OBD-I capability and needing the surge protector, was used in all RWD models up until 1993 (select trim levels only, standard equipment only 1992-on):

Volvo 240 1988-1993 (last model year)
Volvo 740 1988-1992 (last model year)
Volvo 760 2.3l Fuel Injected Turbo 1988-1990 (last model year)
Volvo 760 2.8l Fuel Injected 1988-1990 (last model year)
Volvo 780 1989-1990 (last model year)
Volvo 780 2.3l Fuel Injected Turbo 1991
Volvo 780 2.8l Fuel Injected 1987-1988 (last model year)
Volvo 940 1991-1993
Volvo 940 SE 2.3l Fuel Injected Turbo 1991-1992
Volvo 960 1992
Volvo 960 3.0l 6 cylinder Fuel Injected 1993

Volvo 940 1991-1995
Volvo 940 SE 2.3l Fuel Injected Turbo 1991-1992
Volvo 960 1992
Volvo 960 3.0l 6 cylinder Fuel Injected 1993-1997
Volvo S90 3.0l 6 cylinder Fuel Injected 1997-1998
Volvo V90 3.0l 6 cylinder Fuel Injected 1997-1998

Thanks Dave, I will get back here. Steady rain here today not sure how much time I will put in on it.

Hi Dave,

There's an 1990-93 ABS trouble shooting file in this folder full of Volvo info. (PDF files: some Volvo and some Chilton style stuff that cover many model years)

https://www.allcarmanuals.com/factory-service-manual-310-Volvo-940.html

Bill

Great! Thanks, it's always good to get factory service manual information. I like the step-by-step thoroughness of those.
I will be going through my system, and I will post back to this thread what progress I'm making.
Steve