Shed

I doubt it. I only got the car about three weeks ago and only noticed the pulsating issue a little over a week ago. The car does need new tires so I was hoping that may be what's causing it.

BillJoeBob

Seems a lot of people are having trouble with the ABS malfunctioning (going off) at low speed when it is not supposed to, and that doesn't set a trouble code (DTC). I found a simple diagnostic that takes no more than 30 minutes to complete that will determine if it is a reluctor (tone) ring or possibly a dirty ABS sensor. The procedure requires setting the ABS computer into diagnostic mode and then driving the vehicle a short distance. The procedure is as follows:

Items needed:
1. Two jumper wires (preferably of the fusible type)
2. The location of the Data Communication Link 1 (DCL1).
2. Pen and paper
3. A straight road of at least a quarter mile and no traffic

How to perform the test:
1. Create fusible jumper wires. I used a 5 and 7.5 amp fuse because that is all that I had.

2. Locate DCL1 in the drivers side engine compartment just above the main fuse and relay panel. It is a small black box that says "Diagnositics" on it. Yellow arrow in image.

3. Drive your car to a straight rode of at least 1/4 mile long and without any traffic.
4. Park and turn the vehicle off.
5. Open the hood and DCL 1.
6. Locate terminals Ts and E1 in DCL 1 and jumper together using the fusible link.

7. Start the vehicle.
8. Observe the ABS light flickering at a rapid pace. Everything is fine the ABS computer is now in a diagnostic mode.
***NOTE*** It is important that you drive the vehicle in a straight line at this point. If you don't the computer will likely misdiagnose the faulty reluctor (tone) ring.
9. Put the vehicle in drive and accelerate to 30 mph while driving in a straight line and maintain the speed for a few seconds.
10. Stop the vehicle and put it in park but leave in running.
11. Jumper terminal Tc to E1 using the second fusible link.
***NOTE*** Terminal E1 should now have two fusible link jumper wires attached to it. One going to Ts and the other to Tc.
See image of step 6 above.
12. Return to the drivers seat and notice that the ABS light is now blinking at a different rate than before.
13. Using your pad and pen write down the numbers of blink you observe on paper. A brief pause will be seen between subsequent numbers and a long pause when the sequence starts over.
***NOTE*** DTC for the ABS system will always be two digits

An example - The number 11 followed by 34 and then 78 would be as follows: blink (brief pause) blink (long pause) blink blink blink (brief pause) blink blink blink blink (long pause) blink blink blink blink blink blink blink (brief pause) blink blink blink blink blink blink blink blink (really long pause)

A list of ABS DTCs:


Hope this helps put a close to the ABS pulsating pedal reluctor ring problem. I've now diagnosed mine to a faulty drivers side rear problem. I will not be able to make the repair for a week or so but I will let ya'll know if the ABS computer got it right.

Cheers

MASSMINI

Thanks for the info! Please do update once you know if driver's side rear ring proved to be the problem. Also, what codes did you get that pointed to driver side rear?

amblyn

Its alot easier to unplug abs system then getting the fuse or relAy out pop ur hood and on passenger side see a box with like 4 metal lines coming out of if right infront of windshield washer resevoir or no i lied infront of the coolant overflow take the top plug out will disable abs i have same pulsating drives me nuts doesnt do it all time but when i need brakes they start pumping so i unplugged it i dont need abs as i end up pumping then myself so then gets double pumped haha but yea another thing will trigger this is faulty speed sensors bad abs cpu and also if your reluctor rings are shot will do it if your shocks or struts are shot can throw off readings all kinds of things i didnt wanna go crazy over abs isnt that important to me you know good luck if u fix it pleaaaasseee post how dont ask for help get it and never give feedback haha dont take that as me being rude not my intention

BillJoeBob

Sorry not to get back with the results of the repair. I still haven't been able to do it. I'm planning to pull the drivers side rear half shaft this weekend if the weather cooperates. To answer MASSMINI's question I got an 11, 34 and 78 but only after doing the check as I posted. The original problem presented itself without setting the ABS light. Only a pulsating brake pedal at low speeds as others have also observed. For now the relay is out.

2001cobra

Hello all,
I joined this site because of this issue.
I have a 99 rx300 with a pulsating brake pedal under 20mph. I replaced both rear wheel speed sensors. They are after market ones, not the oem. After installing them, the problem still exists. I think I might not have cleaned the reluctor rings good enough. I will give cleaning them another shot sometime this week.
Does anyone know a place that sells after market rear axles for the AWD rx's?

Thanks,
Eric

Aprazur

I had the same pulsating brake pedal problem when stopping for a traffic light. I replaced the front rotors with Autozone ($30 each) and the rear rotors also ($37). Also installed ceramic pads front & rear. Problem solved. The rear pad lining was original with 120K miles. The front lining (ceramic) was changed @ 60K. It still had 3/4 life left. I changed it any how. Go with ceramic. No brake dust and no squeal ever..

Jerry

maxSteel

If the problem is a failure in the abs then changing pads and rotors is not going to help.

Aprazur

But if the failure is Not in the abs....pads and rotors WILL help.

maxSteel

That's true enough.

I've been assuming the poster tried disabling the ABS to isolate the cause before replacing wheel sensors. It's easy to do and it eliminates the guesswork.

2001cobra

Reluctor rings will be getting cleaned tomorrow.

Hopefully that fixes my pulsating iussue.

maxSteel

Hope that does it. Mine was cracked and no longer solidly locked to the half shaft.. I could reach through the sensor hole and move it.

2001cobra

Sadly, my left rear reluctor ring was broken as well.

MASSMINI

Please tell us your experience it getting the axle out...

2001cobra

It seemed daunting but wasn't too bad. I used this great write-up to get the axles out.
https://www.clublexus.com/forums/rx-...tone-ring.html
I also plan on replacing the reluctor ring on the current axle as a spare.

I ordered a used axle for the RX for a faster install. Should arrive tomorrow.