Novak Conversions Jeep Wrangler JK engine mounts

C0021 Brake Booster Performance code after replacing booster

C

Cosmo5754

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Michigan
I recently replaced the power brake booster, brake booster vacuum sensor, brake light switch, and air pump. After completing this I did a brake flush and bled all of the calipers. I am still getting a stiff brake pedal and a C0021 code. After replacing the brake booster with a second new unit there was no improvement.

While on the test drive after the second brake booster I got a U0414 code and the car started acting sluggish. Car seems to be in limp home mode and the transmission refused to let me shift it using the auto-stick, but I confirmed that the 4WD is still functional. After letting it sit for an hour that has gone away.

I have replaced everything in the power braking system minus the master cylinder so I don't really know where to go from here. Thank you!

*Edit* Before replacing the parts I had the C0021 code and the stiff brake pedal. I replaced the vacuum pump and brake booster at that time problem was solved minus the brake light switch but after replacing that everything worked. It then gave a code for the yaw rate sensor so I also replaced that. Then the car was down for a bit for a failed head gasket so after finishing that job the brake issues returned.

2014 Wrangler Unlimited Sahara 3.6
 
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What were the issues BEFORE you replaced the parts?

By stiff pedal you mean no power boost?

I’d be looking at the vacuum lines and check valves for a vacuum leak.
 
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Mopar said:
What were the issues BEFORE you replaced the parts?

By stiff pedal you mean no power boost?

I’d be looking at the vacuum lines and check valves for a vacuum leak.
Click to expand...
Before replacing the parts i had the c0021 code and the stiff brake pedal. I replaced the vacuum pump and brake booster at that time problem was solved minus the brake light switch but after replacing that everything worked. It then gave a code for the yaw rate sensor so I also replaced that. Then the car was down for a bit for a failed head gasket so after finishing that job the brake issues returned.

I believe the stiff pedal means no power boost but this is my first time dealing with brake stuff. When I push the pedal not much happens and it feels like the pedal is pulsing. It is also quite hard to push the pedal.

I checked all of the vacuum lines for leaks and none of them seem to be leaking. I forgot to mention that the T fitting that connects the vacuum pump, brake booster check valve, and intake manifold broke when removing it. I picked up a new one at autozone and added hose clamps to make sure it wouldn't leak.
 
I’d be looking at the check valves between the booster and the engine and the booster and vacuum pump.

Pull the vacuum line to the booster off with the engine running. Is there vacuum? Measure it with a vacuum gauge. What’s the reading?
 
Mopar said:
I’d be looking at the check valves between the booster and the engine and the booster and vacuum pump.

Pull the vacuum line to the booster off with the engine running. Is there vacuum? Measure it with a vacuum gauge. What’s the reading?
Click to expand...

Where are the check valves? I thought the sensor that was on the brake booster was the check valve, is there another one somewhere? I don't currently have a vacuum gauge but before I get one I took the line off, when the engine was running, and tried to feel if there was any vacuum and there was not. Today I also changed the wheel speed sensor on the driver front wheel as it seemed to be directly connected to the vacuum pump.

I will go get a vacuum gauge to test that anyways.
 
If you have no vacuum at the booster with the engine running, there’s your brake problem. Now you have to figure out why you don’t have vacuum. I’d inspect your check valves. Follow the hoses and you’ll find them. My 2016 has two and I assume yours does too.

Don’t worry about your vacuum pump at the moment. The engine supplies most of your brake vacuum anyway.

Pull the vacuum hose at the manifold with the engine running. Do you have vacuum? Then, connect a piece of new hose directly from the vacuum port on the intake manifold and then run it to the brake booster and connect it. Does the booster work now?
 
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