The car is a 1991 245SE.

A month or so I was in traffic, in heavy rain, and had to drive through a pretty big puddle. It wouldn't surprise me if it was deep enough to reach the ABS sensor. As I drove through the puddle the ABS light came on. After restarting the car the light is off, but comes back on when the car reaches about 70MPH. I figured some crud got in there, so I took both front sensors out and cleaned them, and stuck a brush in the opening and cleaned the tone rings as well as posible. There were some chunks of rust stuck to one of the sensors, but even after cleaning the light still comes on at 70MPH or so.

What's my next diagnostic step?

We've owned Volvos since 1973 (when I bought my first, a new 164), so you could call me a Volvo enthusiast. But I've discovered some drawbacks very lately which I attribute to the relatively recent period of Ford ownership.

It used to be, for most of the decades that I owned Volvos, that I could easily get parts (genuine Volvo parts) from the dealer's parts counter even when my cars were 20 years old -- I've always been reluctant to buy third-party brands because of some bad experiences. Anyway, lately I've found that it's hard (or even impossible -- i.e., NLA, or "No Longer Available") to get certain Volvo parts for my latest model year cars (both '93s) -- the regional warehouses don't keep inventories of reasonable (i.e., those likely to be needed over the years) parts anymore, even those for critical systems like brakes!

Case in point for your ABS system, the overvoltage relay, at least for my two '93s. Just can't get it anymore, so I now drive around with a non-working ABS (which wouldn't be so bad if they still had the rear pressure limiters, but that was removed in favor of the ABS -- assuming it works). There have been other examples of NLA parts, but your inquiry just gave me the incentive to write and complain.

Wish China, Volvo's new boss, would contract for the production of new batches of these NLA parts, as if that would ever happen :-( .

Later this summer my wife and I are planning to buy a couple of new Subarus. They may not last as long as our old Volvos, but at least I won't be disappointed if they don't -- my expectations for these last Volvos were too high.

Thanks for letting me get this off my chest -- and I hope that you can solve your problem without too much aggravation.

any misbehavior from the speedo, or a code involving the vehicle speed sensor? A 3-1-1 error does NOT trip a check engine light, so you may have the code and not know it.

Although the rear sensor on the differential rarely has problems, the wiring to the sensor is a common trouble spot. The short length between the connector and the end of the protective sheathing often suffers from decayed insulation, leading to a short in really wet conditions.

john

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1989 245 245K / 1993 945 131K

Ok, I'll check the wires going to the diff and look for codes. What does the 3-1-1 code mean?

There's no wacky behavior other than the ABS light. The car has about 250K miles on it and runs like a top for the most part.

3-1-1 is the ECU not getting a vehicle speed signal. It can indicate an intermittent wiring fault that, for one reason or another, is not always evident to the driver via the speedometer. I mentioned it because it has been a source of trouble with my 940's ABS.

Looking at the 1991 wiring diagram, I see the ABS computer is at the head of the line for the signal from the rear sensor. Sensor>ABS computer>signal converter>speedometer>ECU

The ABS greenbook TP-31678 has seven pages of system checks to perform with a multimeter in order to determine the source of a fault. (A little too much to retype in full)

some basic checks lifted from greenbook:

with ignition off:
-disconnect harness connector from ABS computer, and connector terminals
10, 20, 32 ,34 should show ZERO ohms to ground

ignition on:
-on ABS relay, terminal 1, 2, and 4 should show battery voltage to ground. Terminal 3 should show ZERO ohms to ground. Relay must be in connector, you've got to slide the probes up the back side of the connector and check from the rear.
-on computer connector, you should see battery voltage between terminals 7 and 9, indicating correct function of converter unit.
-should see battery voltage between terminals 27 and ground, 28 and ground, and _with brake pedal depressed_ terminal 25 and ground.
-should see .5-1.0 volts between 29 and ground.
-start engine, check for battery voltage between 15 and ground.

ignition off:
-check front sensors at computer connector. should see .9 to 2.2 kilo-ohms between terminals 4 and 6 (front left) and between 11 and 21 (front right).
-check rear sensor at computer connector. should see .6 to 1.6 kilo-ohms between terminals 7 and 9.

If you've never run tests at a harness conenctor before, be aware that the correct way to check is thru the test ports on the SIDES of the connector. There's a hard plastic comb-shaped thingy stuck in there, usually in a contrasting color plastic, which should be gently pried out to expose test ports. You DON'T want to be poking probes into the delicate spring-connectors that mate with the blades on the computer.

good luck!

john
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1989 245 245K / 1993 945 131K

That's fantastically helpful, thanks!

I'd never expect you to type out all seven pages from the greenbook, however I'd have no problem sending you a couple of bucks to cover your time if you'd be willing to scan the relevant pages for me. Or if you're near NYC I'd be happy to buy you a beer.

But, hopefully none of that will be necessary. I've got my fingers crossed that the info above will get me sorted.

Thanks again.

sadly, all I have for this book is the recent DVD from OTP (which you can buy from FCP Groton, Volvo Club of America, and others). Nice quality scans but the anti-piracy protections are slathered on so thick it is functionally nearly useless. Cannot print, cannot do screen capture, cannot use on more than one computer, cannot use on a machine without internet. Hate it, have nothing but evil thoughts directed to OTP and LockLizard for offering a product with such little practical value.

Although there's a copy of the 1991 ABS Brakes 240 greenbook on Ebay right now for the low low price of $80.

If any of those tests turn up the fault, post back and I can look up further details for that item.

John

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1989 245 245K / 1993 945 131K

I had considered buying that DVD until I heard all the complaints about it. If it were $5 I'd buy it, but considering people's reviews it sounds like I'd be buying a ferrari that's electronically limited to 35MPH. I don't have the $80 to plunk down on ebay right now, but I'm much more inclined to do that than pay for the DVD everyone is having so much trouble with. I keep a computer in the garage, but it doesn't consistently have an active internet connection, so it would be useless for me.

Anyway, more importantly, thanks for all the help! I think my girlfriend might have me monopolized for the next few weekends, but if I still need help once I'm able to escape to work on the car I'll look for you.

Thanks again!