C1256 ‘accumulator low pressure’

[Jakeepoo3]

I reset everything and drove very gingerly for 5 miles and the codes came back. No tires rubbed during those 5 miles.

All I need is a way to read DTC codes. I can follow these simple procedure to determine if C1256 is an actual issue or caused by something else.

In my case I caused the code. Toyota has this to say about C1256

You have to initialize/learn the PCM because you unplugged the sensor.. you can pull codes at home in the driveway..

 

[Jakeepoo3]

Yeah follow that hint and quit tripping those codes.

 

[Jakeepoo3]

Jake Gore - 33"s on the lady here in a minute ?

Body mount chop about an hour or so.

 

[1950884]

Got a 2006 V6 w/ 195k miles. Has been trouble free for 65k miles and now needs some love. My dash is lit with VSC Off / pic of car skidding, VSC Trac, & Check engine.

A) With the truck off and parked, cycling the brake doesn’t result in much of an increase in pedal pressure. I pumped 50 times. It gets a little more stiff but I can still press the pedal to the floor. Is what I described normal or is it indicative of an internal leak in my brake master cylinder?

This is normal: (2) Depress the brake pedal 20 times or more to release the pressure in the accumulator. HINT: When the pressure is released, the brake pedal stroke becomes longer.

B) After performing the above, turning the key on (motor not running) the brake pump ran for 8 to 10 seconds. Pressing the brake once cause the pump to run for 2 to 3 seconds. Press the brake again and the pump runs for 2 to 3 seconds. Repeat. This Informs me that the accumulator is not functioning, because it should hold more pressure than 1 brake pump. Do you agree?

This is NOT normal: (5) Turn the ignition switch to ON and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops). OK: 20 to 80 seconds

(10) Depress the brake pedal 4 or 5 times and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops). OK: 2 to 11 seconds

I suspect a defective accumulator, pressure sensor or very unlikely both.

That rub could indeed affect your skid ECU. Speed sensor and steering angle sensor may be thrown off detecting the rub. Both are skid inputs. You need to do a few things it sounds like. Most importantly body mount chop. Next check test o2 sensor with a multimeter and propane torch. Replace if bad. Next complete initialization/learn procedures. Reset skid zero points.

I really don't want to go down the modification path. That is what my MR2 is for. Based on failing the test Toyota has designed to isolate testing the brake system irrespective of skid ECU, my 4runner is not in spec.

 

[Jakeepoo3]

Here's the complete procedure. These things tend to have to be done in specific proper order. Mentions the warning lights you have or shouldn't during this test... Also the buzzer. I'm just more into paying a few dollars for the minor causes of the problem to see if it fixes before I pay big cash for something I don't need. If you wouldn't have broken that speed sensor you'd probably already know either way.

 

[1950884]

Here's the complete procedure. These things tend to have to be done in specific proper order. Mentions the warning lights you have or shouldn't during this test... Also the buzzer. I'm just more into paying a few dollars for the minor causes of the problem to see if it fixes before I pay big cash for something I don't need. If you wouldn't have broken that speed sensor you'd probably already know either way.

I followed the procedure start to finish. The ABS plastic body is cracked but the sensor is still functioning. I do appreciate you trying to save me money!

 

[Jakeepoo3]

I followed the procedure start to finish. The ABS plastic body is cracked but the sensor is still functioning. I do appreciate you trying to save me money!

If the speed sensor is still functioning it's really weird how you got two new speed sensor codes. By the way this will cause all the same lights to come on and disable the skid ECU the same as the O2 sensor did. I see that o2 code went away. Be interesting to know if everything is working correctly after you replace the speed sensor before replacing the accumulator. Either way works I guess.

 

[1950884]

According to factory manual BR-3 ‘brake fluid bleeding after replacing the brake accumulator’ the hydraulic pump should operate for 8 to 14 seconds. Mine clocked in at 12 to 13 seconds. I haven’t had any check engine codes since installing. I might pay toyota $125 to bleed the master and brakes but the brakes feel great so this is not necessary. Consider the problem in the OP solved unless I return to this thread.