Tha ABS lamp has recently been coming on on my son's 740 Turbo Wagon. All the lights come on with the ignition in the on position and goes out when we start it. As soon as I put it in drive the light comes on again and stays lit. The Haynes says there are no codes for the 90-91 so the control module has to be dignosed with multi-meter. Ugh!! I just did his front brakes including new rotors about 6 months ago. I fixed bad wiring on the rear sensor last year and it seems to be holding up. I know the sensors are the easiest thing to check. Where is the connector for the front sensors? Haynes isn't very clear where they are. Are they in the wheel well, or on the modulator under the hood?

We've had endless problems with the ABS on my parent's 1990 740. Very similar to what you describe except it also exhibited low-speed pulsing of the ABS intermittently. Usually cleaning the front sensors helps for a while. The front brakes on this car have VERY dusty pads which badly contaminate the sensors.

As an experiment, I swapped the sensors from my 1991 940 into the 740 (and put the 740's in mine) about 5 months ago and they haven't had a problem since but neither have I. The 940's sensors are a diamond shape whereas the 740 has square shaped heads. The square sensors are too sensitive and don't like being covered in brake dust.

Not sure what type you have on your son's 740 but might be worth checking. When budget allows I'm going to replace the sensors on the 740 with the diamond-shaped ones.

Good luck
Brad
91 940GL

Hi,

The connectors look JUST like the one on the diff for the rear axle. They're located on the outboard sides of the strut towers under the hood. Look for gray "D" shaped connectors with two conductors. I've found that the sensors are the most common failure item with ABS systems in 700 series Volvos. Usually cleaning up the connectors helps.
--
D '90 745T 229k, '88 744GLE 129k, '96 328i, '73 911T 100k+

That was my issue.

Now is a good opportunity to clean and protect every connector in the engine compartment.
--
Paul NW Indiana '89 744 Turbo 145K/ '90 745 turbo 127K