C1256 ‘accumulator low pressure’

[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?

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?

 

[Jakeepoo3]

What are all the DTC codes?? That code can be thrown for a number of reasons. Usually it's not the problem, but rather a skid ECU input. Or possibly your skid ECU got a whacky signal and malfunctioned.

 

[Seymore Butts]

Assuming you have no visible leaks, and there's fluid, that's the classic symptom of brake system failure. There are lots of threads here about replacing or rebuilding. Neither option is cheap, unfortunately.

 

[1950884]

What are all the DTC codes?? That code can be thrown for a number of reasons. Usually it's not the problem, but rather a skid ECU input. Or possibly your skid ECU got a whacky signal and malfunctioned.

The entire list is at home. There were 8 codes total. Three of which were the same code. ABS sensor, ECU, etc. I will post the entire list tonight after work.

Assuming you have no visible leaks, and there's fluid, that's the classic symptom of brake system failure. There are lots of threads here about replacing or rebuilding. Neither option is cheap, unfortunately.

The brake fluid level remains steady. I might have added up to a half pint in the last 65K miles or 8 years. No fluid on the floor or around the brake master cylinder in the last several months.

I have searched this board & the web extensively for '4runner C1256.' There were only 15 unique posts on the msg board. The advice was generic. Some replaced the entire assy (MC, pump, & accm for thousands of dollars) or individual components for a few hundred. Their results were mixed with success and failure. Nobody gave definitive suggestions on how to identify exactly which component to fix. I ordered the accumulator only and will report back my results.

 

[Jakeepoo3]

The entire list is at home. There were 8 codes total. Three of which were the same code. ABS sensor, ECU, etc. I will post the entire list tonight after work.

The brake fluid level remains steady. I might have added up to a half pint in the last 65K miles or 8 years. No fluid on the floor or around the brake master cylinder in the last several months.

I have searched this board & the web extensively for '4runner C1256.' There were only 15 unique posts on the msg board. The advice was generic. Some replaced the entire assy (MC, pump, & accm for thousands of dollars) or individual components for a few hundred. Their results were mixed with success and failure. Nobody gave definitive suggestions on how to identify exactly which component to fix. I ordered the accumulator only and will report back my results.

Probably a free fix. I've had this code numerous times. Check out this thread I made with a similar issue. Better suggestions come with more information!

 

[Jakeepoo3]

VSC, A-TRAC, DAC functions disabled, solution

 

[1950884]

VSC, A-TRAC, DAC functions disabled, solution

I looked at your post. While it didn't include C1256, it is very interesting to see how the different DTC codes interplay (feed back & feed forward) on each other. I will attempt to clean my ABS sensor tonight.

I have good reason to believe that I have a braking issue because of the explanation I gave in my opening post. Is what I explained in part A & B of my OP normal?

When I searched I didn't find anybody that experienced the exact same codes as me. Perhaps I should pay the $125 to have Toyota diagnose my situation.

I appreciate your help.

 

[Jakeepoo3]

I looked at your post. While it didn't include C1256, it is very interesting to see how the different DTC codes interplay (feed back & feed forward) on each other. I will attempt to clean my ABS sensor tonight.

I have good reason to believe that I have a braking issue because of the explanation I gave in my opening post. Is what I explained in part A & B of my OP normal?

When I searched I didn't find anybody that experienced the exact same codes as me. Perhaps I should pay the $125 to have Toyota diagnose my situation.

I appreciate your help.

I did have that code also it disappeared before I did that diagnostic. Booster and accumulator. When your brake went crazy it caused them to malfunction due to whacky input signal to your skid ECU/master cylinder. It's not broke I would bet money on it. Can you show us all the codes so we can help you better! Maybe save a a grand or two.

 

[Jakeepoo3]

I've also had that code after neglecting to re calibrate my zero points after a 3" lift. Mine did what you said on a sharp right turn and nearly killed a granny.

 

[1950884]

Three times C0606 Engine Control Module Processor.
P0137 O2 sensor bank 1 sensor 2 low volt.
C1201 Engine Control System Malfunction.
C1233 Malfunction in antilock brake system control system.
C1241 Low Battery Pos Volt.
C1256 Accumulator Low Pressure.

Maybe I should clear the codes and then drive it to autozone/advanced auto to have them check for current codes?

I've also had that code after neglecting to re calibrate my zero points after a 3" lift. Mine did what you said on a sharp right turn and nearly killed a granny.

Interesting. I do have a 3 inch-ish lift.

 

[Jakeepoo3]

Three times C0606 Engine Control Module Processor.
P0137 O2 sensor bank 1 sensor 2 low volt.
C1201 Engine Control System Malfunction.
C1233 Malfunction in antilock brake system control system.
C1241 Low Battery Pos Volt.
C1256 Accumulator Low Pressure.

Maybe I should clear the codes and then drive it to autozone/advanced auto to have them check for current codes?

Interesting. I do have a 3 inch-ish lift.

No don't clear them yet or if you do write all that down. O2 sensor causes all those codes and also disables your skid ECU.. need to check your battery also for proper voltage.

 

[1950884]

No don't clear them yet or if you do write all that down. O2 sensor causes all those codes and also disables your skid ECU.. need to check your battery also for proper voltage.

What is your source for saying "O2 sensor causes all of those codes and disables your skid ECU?"

Battery volts were low 13's before starting vehicle and high 13's when idling. I have an OE Denso 234-4260 O2 sensor I am going to install right now.

 

[Jakeepoo3]

What is your source for saying "O2 sensor causes all of those codes and disables your skid ECU?"

Battery volts were low 13's before starting vehicle and high 13's when idling. I have an OE Denso 234-4260 O2 sensor I am going to install right now.

Experience and knowledge. $2000 worth. O2 sensor is a ECM input thus your ECM code. O2 sensor is an input to skid ECU through ECM. Skid ECU disabled without O2 sensor input. The abs code is due to your disabled skid ECU. The braking problem you had is due to your skid ECU not getting proper input signals and it disabled itself. Your brakes still work right?

 

[Jakeepoo3]

What is your source for saying "O2 sensor causes all of those codes and disables your skid ECU?"

Battery volts were low 13's before starting vehicle and high 13's when idling. I have an OE Denso 234-4260 O2 sensor I am going to install right now.

You should be running around 14 to 14.5 volts in charging mode.

 

[1950884]

I've also had that code after neglecting to re calibrate my zero points after a 3" lift. Mine did what you said on a sharp right turn and nearly killed a granny.

How all of these systems interact is becoming clearer. My trouble is that I've driven the vehicle exactly how it currently sits without any engine codes (at least not that I was aware of).

I bought the vehicle with a 3 inch lift and the tires hit the frame, fender and liner, so I changed from mud tires to less aggressive off road, I also had the frame cut to accommodate oversized tires. Now the tires very seldom rub. But when they do rub the car VSC Atrac etc alerts go off.

 

[1950884]

You should be running around 14 to 14.5 volts in charging mode.

I re-measured, 12.6 while off and 13.9 while idling. Taken from the battery.

 

[1950884]

Experience and knowledge. $2000 worth. O2 sensor is a ECM input thus your ECM code. O2 sensor is an input to skid ECU through ECM. Skid ECU disabled without O2 sensor input. The abs code is due to your disabled skid ECU. The braking problem you had is due to your skid ECU not getting proper input signals and it disabled itself. Your brakes still work right?

Yes, the brakes seem to function properly. After installing the new O2 sensor & trying to pry one of the ABS sensor out (started to crack the case so stopped) I cleared the codes and drove about 5 miles to the auto part store. New codes:
C0200 Right ABS sensor malfunction
C0205 Left ABS sensor malfunction
C1223 General ABS system fault
C1241 Low battery positive volt
C1256 Accumulator Low Pressure...Confession: This might have occurred because I tested the brake by pumping them 7 to 8 times while idling and the ABS warning light came on and it buzzed. Unfortunately the Accumulator is already on order.

I wish I had techstream -> Procedure to troubleshoot C1241 Low Battery Post Volt.

 

[Jakeepoo3]

How all of these systems interact is becoming clearer. My trouble is that I've driven the vehicle exactly how it currently sits without any engine codes (at least not that I was aware of).

I bought the vehicle with a 3 inch lift and the tires hit the frame, fender and liner, so I changed from mud tires to less aggressive off road, I also had the frame cut to accommodate oversized tires. Now the tires very seldom rub. But when they do rub the car VSC Atrac etc alerts go off.

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.

 

[Jakeepoo3]

Yes, the brakes seem to function properly. After installing the new O2 sensor & trying to pry one of the ABS sensor out (started to crack the case so stopped) I cleared the codes and drove about 5 miles to the auto part store. New codes:
C0200 Right ABS sensor malfunction
C0205 Left ABS sensor malfunction
C1223 General ABS system fault
C1241 Low battery positive volt
C1256 Accumulator Low Pressure...Confession: This might have occurred because I tested the brake by pumping them 7 to 8 times while idling and the ABS warning light came on and it buzzed. Unfortunately the Accumulator is already on order.

I wish I had techstream -> Procedure to troubleshoot C1241 Low Battery Post Volt.

You're causing more problems not fixing them. Now you need a new speed sensor. After you replace any PCM input you have to do the initialization and learn procedures.. quit doing that brake thing that would happen to anyone doing that..

 

[1950884]

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

HINT:
Excessive brake pedal operation results in abnormal accumulator pressure consumption. This is normal.