ABS issues in need of some help

[Erik Steinbring]

I have a 2004 SR5 V6 with 165K and it has ran like a top since I purchased it. Yesterday morning it it reared an ugly head. I was sitting at a stop light and the brake pedal began to pulsate then the dash lit up like a Christmas tree. Brake/ABS/VSC On/Trac OFF and a buzzer from hell all came on. I drove home the 3 miles with a bottomed hard brake pedal.

I pulled the ABS codes and had a 51 and 56........

51- Pump motor locked
56-Accumulator low pressure malfunction

Somehow I was able to get the brakes restored in the afternoon with only the VSC On/Trac Off lights on.

This morning I went to start up the vehicle only to find a bottomed out hard brake pedal again with the all the lights and buzzer. I pulled the codes to reveal ABS codes 51, 52 and 56. I am not sure what the elves did while I was sleeping but I was at a loss.

51- Pump motor locked
52- Hydraulic booster pump motor malfunction
56-Accumulator low pressure malfunction

I checked all the relays disconnected the battery, drove the vehicle with a bottomed out hard pedal and now it only shows a ABS fault of 56.

So since I was able to get the system restored once I believe I can rule out the booster pump motor. Which leads me to the pressure switch of which I cannot find any information as to a part number or how to replace it. The Accumulator low pressure malfunction I believe I can rule out as it would be a direct result of a bad pressure switch.

So if my logic is good I believe I need a new pressure switch. Is there a relay for this switch? What do you think? Am I missing a component?

Any help would be greatly appreciated! I feel like I am chasing a ghost!

 

[Erik Steinbring]

All I can find is a Master Cylinder Oil Pressure Sensor Part# 89637-60020.............Would this be the same part listed as a "Pressure Switch" in the diagnostic?

 

[BCfish]

Good luck I hope it's not like mine. I just had the same issue on my 03 V6 and it was my ABS pump needed a whole brake master cylinder assembly. That was 2 weeks ago still waiting to get the truck back part came in yesterday which was back ordered. [MENTION=66389]BlackWorksInc[/MENTION] might have a few more insights on what else it may be.

 

[BlackWorksInc]

Well the sensors can go bad and they have in the past. I can't remember how they read pressure if its an on/off switch or if its some sort of varying voltage.

Depending on how the switch/sensor works you may be able to test it with DMM to at least try and rule it out? I'd need to find more information.

 

[Erik Steinbring]

Thank you for the replies!

I tinkered with the system this evening and this is what I found. I disconnected the master cylinder pressure sensor and it threw up a code 46 that there was a malfunction. So I reconnected the sensor and can cross off pressure sensor.

I decided to tap on the top of the Accumulator with a pair of pliers as well as the booster motor.......I know not overly scientific but the pump started working. I could the feel the pump vibrating through the pedal when I was inside the vehicle when it was running. A plus was the ABS and brake dash lights turned off and I once again had brakes.

I took it for a spin around the block and in short time the lights were back on I tapped the top of the accumulator a few times and again the pump fired up and the lights disappeared brakes were restored. Took it for another short drive and again lights and bells however I never lost pedal.

Again I tapped the top of the accumulator and the pump cycles but now for maybe 2 seconds at a time and stops.....I tap it again and it runs another couple seconds.

It almost seems like air is being compressed or something? It will run just about every time I tap on the accumulator few times.

It still is throwing the accumulator low pressure malfunction code (Code 56) so that is all I found out this evening.

Any ideas?

 

[gmccune13]

I am having very similar issues with my 2005 4Runner. Very little brakes the Christmas tree lights and the alarm from Hell. Did you ever figure out definitely what was wrong and how to fix?

Thanks!

 

[1kramer1]

Having the same issue. What eventually was the fix for you?