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?

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.

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 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!

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.

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.

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.

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. 👌🤠

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?

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

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.