Multiple ABS problems in 2000 V70

[FireFox31]

Why would the ABS engage each time I press the brake pedal on poor Geronimo? It's a Canadian 2000 V70 NA automatic with 350k miles. I just replaced all pads and rotors, three calipers, and the brake fluid. I installed a Midwest ABS rebuilt module which restored the speedometer and removed dash lights and stored codes. Still, multiple ABS problems remained.

When the ABS engages, the ABS unit makes a rapid grinding sound, the pedal pulses rapidly against my foot pressure, and the car doesn't seem to slow any differently. The ABS light does not flash.

The ABS frequently engaged while coasting over 25 mph without pressing the brake pedal. Pressing the brake pedal moderately would stop the ABS. I cleaned the front reluctor / reluctance / tone rings, removing rust scale (I had already cleaned the rear rings). That resolved this problem.

The ABS engages the majority of times I press the brake pedal. It doesn't stop until I release the pedal or the car stops. Sometimes it continues after releasing the pedal. It doesn't stop when I press the pedal moderately like in the above situation. The strength of the ABS engaging varies from vigorous to barely audible.

The brake pedal sometimes has decreased travel, pushes back once per tire revolution, clicks once per tire revolution, and has decreased stopping power. This happens as the ABS is engaged during breaking. This happened rarely on my last V70, would stop if I let off the break and reapplied it, and was accompanied by none of these other ABS failure symptoms.

This ABS engaging may have been happening for any amount of time. Could prolonged engagement have burnt out some ABS component? Before my work, a front caliper was seized pressing on the rotor, both rear calipers were frozen, and the parking brake shoes were dragging terribly. Imagine the ABS trying to engage with the brakes in that bad condition.

I tried my rebuilt ABS unit in the car (same part number and manufacture date) and the problems were the same. The Midwest ABS unit is the awkward part # 8619538 manufactured Nov 2003.

The ABS unit has rust at the base of four cylinders. Could that be a problem? What are those cylinders?

The car currently has two DTC codes:
P1671 CMP Actuator Performance Problem or Signal Out Of Range
P0135 O2 Heater Circuit (Bank 1, Sensor 1)
Neither of these seem related to ABS.

I will try to probe the electrical components, but I'm vastly inexperienced at that so worried I'll waste time doing it wrong. What else can I check?

[abscate]

I think you need to monitor wheel speed condition at each wheel to see what signals are coming from each one to see what is triggering it. Do you have a scanner that can do that? I can send you mine if you don’t.

I don’t like the condition of those tone rings, but short of axle replacements , there isn’t too much else one can do. Does the car self test the AbS with the little burp when you first exceed 15 mph?

Last exotica, sticking master cylinder. Rare but can happen. I do have spares on the FDPP for that. This points me there.

Sometimes it continues after releasing the peda

In mean time, pull the power plug for the ABS MOTOR , leave the logic connector in, and you can drive it. See if normal brake function is there.

IF (Driver = MALE AND AGE > 25) OR ( Driver = FEMALE) = TRUE you can run the car long term without ABS

[FireFox31]

Thanks for the input. I don't have a scanner so I'm going to order a VIDA laptop now.

I think the master cylinder is ok. The brakes work well with the ABS module harness and power disconnected. Each rotor face is being contacted, removing the Zimmermann silver coating and any surface rust when it sits.

In mean time, pull the power plug for the ABS MOTOR , leave the logic connector in, and you can drive it. See if normal brake function is there.

What plug is this? Is it the black, two-wire plug between the ABS module and the black cylinder on the hydraulic unit? I was planning to pull fuse #4, but that's also for the immobilizer and more.

Reluctor / Tone rings, part 30735955, are available from FCP. $5 for Febi, $30 for Volvo on clearance (identical to Febi?). A P2 thread documents ring replacement and references a ring replacement video. I'm planning to replace both front rings and both outer CV boots when I do the suspension rebuild in the future.

I'll listen for an ABS self test at 15 mph. The self test occurs at 25 mph according to this thread citing VIDA, perhaps specific to 850. That agrees with my ABS engaging at coasting only over 25 mph. Cleaning the rings stopped that problem.

IF (Driver = MALE AND AGE > 25) OR ( Driver = FEMALE) = TRUE you can run the car long term without ABS

ELSEIF (Location = MAINE) AND (Goal = WINTER_SAFETY) = FALSE. This is why the owner insisted on studded snow tires. I'm really trying to get the ABS working so this car will break safely.

[abscate]

That’s the right plug Firefox

The black cylinder is a motor that spins an eccentric shaft that compresses TWo pistons in the aluminum module to generate brake pressure. It’s Hades to put it back together so don’t pull it apart without time on your hands

VADIS says that

"The control module also checks continuously for breaks in the circuit. The control module checks the pump motor by activating it the first time the car reaches 20 km/h (25 mph) i

Hmmm. Someone at VADIS went to Gimli university and then worked on the Mars NASA program it seems

[FireFox31]

Unplugging the power cable at the ABS module stopped the ABS from engaging every time I pressed the brake pedal. The speedometer still works and the brake works fine. Thanks for that tip.

Do you have a scanner that can do that? I can send you mine if you don’t.

I contacted the MVS user who sells VIDA laptops but haven't heard back. What kind of scanner do you have that can read wheel speed data, etc? I'd love to borrow it but I'm not sure when; I've got to give back Geronimo and don't know when I'll get it back.

[abscate]

I have an older AUTEL 800-series with software for most cars, it does by BMW, VWs, and Volvo. It’s about $199

I think this is current version

https://www.amazon.com/Autel-Combinatio ... =1-48&th=1

[manovlov]

Hy Firefox

I had the same kind of issue with my 850. I've replaced the front ABS RELUCTOR rings (the rear ones were as new) and the 4 ABS sensors. To install the new reluctors in place, i warmed them very carefully to expand steel, then, with a plier, put them in place and that was it.

I agree with abscate, what i see on the picture before/after is not marvellous.

Keep courage !


Manov

[FireFox31]

What components are involved in the ABS deciding to engage the ABS? Reluctor rings and their sensors, but what else?

Where does the speedometer data come from? Is it from the reluctor rings?

When the reluctor rings were rusty, the ABS engaged when coasting and breaking, and the speedometer worked. I cleaned the front reluctors, the ABS stopped engaging when coasting, it still engages when breaking, and the speedometer works the same.

The reluctor rings are clean enough to not engage the ABS while coasting so why would they cause it to engage while breaking? I suspect some other part has failed but I don't know all of the components of the ABS system.

[abscate]

It could be the braking force changes the geometry of sensor to ring enough to glitch the ABS system, speculation.

Hmmm..where does a 1999-2000 car get the speedometer reading? That’s a good one. it’s not like the -1998, as the later ABSand DIM talk on the CANBUS

You really need to get wheel speed sensor readings. I’ll confirm my scanner does it on a DENSO 1999 y]that visits tonight.

I might have four steelies forvGeronimo for you.

[manovlov]

It could be the braking force changes the geometry of sensor to ring enough to glitch the ABS system, speculation.

I'm not an expert. But i think abscade is on the right way with his explanation. If sensors are at the same point of tiredness as the rest, you may have a point of start to solve the issue.