# Problem with Power Assist brake losing vacuum 2013 Cruze



## m2carb (Sep 11, 2015)

Good morning,

We have a 2013 Chevy Cruze which is having an issue with losing vacuum for the brake power assist, makes the brake pedal really hard to push down intermittently. This is a 2013 so it is not covered under the recall for the micro switch.

In May, the stop light switch was replaced at the brake pedal, and it seems that this issue started after this was changed. 

It is my understanding that the Cruze uses a microswitch mounted in the vacuum line by the brake booster, which turns on a vacuum pump as needed to boost the vacuum available for the brake boost system. my question is what activates the microswitch? Is the stop light switch part of this circuit and perhaps this part of that switch is intermittently failing? Any help in diagnosing this is greatly appreciated.

Thank you,
Chris L.


----------



## Jim Frye (Mar 16, 2011)

Did a search of this site for "power brake microswitch" and got this. 

http://www.cruzetalk.com/forum/gtse...f=www.cruzetalk.com/forum/&ss=6776j3043290j23


----------



## m2carb (Sep 11, 2015)

This is a 2013, recall for 2011-2012 only, this seems to have started after the brake light (stop) switch at the brake pedal was replaced. Hoping to verify that switch is what supplies power to the microswitch/vacuum pump circuit before spending the $70 on a new switch.


----------



## obermd (Mar 3, 2012)

How many miles on your Cruze?


----------



## m2carb (Sep 11, 2015)

around 10K, but it gets interesting because there is a salvage title on it.


----------



## Jim Frye (Mar 16, 2011)

m2carb said:


> around 10K, but it gets interesting because there is a salvage title on it.


Oh Boy! Any idea who did the rebuild? Was it a flood car? All bets are off now.


----------



## m2carb (Sep 11, 2015)

Yes I do know who did the rebuild and it is a flood car. It is my son's car. I know things can get interesting when water is involved, I am an electronics technician with 34 years experience. And I definitely know flood cars should be avoided, but it was not my decision.

Getting back to my original question, what activates the power to the microswitch/vacuum pump circuit, is it the brake stop switch? It got replaced because the brake lights were not coming on and the car would not start, seems like the problem started right after that switch was replaced by the place that sold it to him. I would get a new switch to replace, what I imagine is a used one, if that could be the problem.

Please, I know the hazards of buying a rebuilt car, just trying to diagnose the problem here, any help in that regard is greatly appreciated, short of purchasing the wiring diagrams for the car, I am hoping to get an idea here. Thanks.

Chris


----------



## brian v (Dec 25, 2011)

Quick guess .......you may have wiring harness issues ...........


----------



## m2carb (Sep 11, 2015)

yup, could be, still looking to find out what activates the power to this microswitch vacuum pump circuit, does it come from the brake switch activated by the brake pedal?


----------



## ChevyGuy (Dec 13, 2014)

m2carb said:


> In May, the stop light switch was replaced at the brake pedal, and it seems that this issue started after this was changed.


It's not a switch. It's a position sensor. And it's supposed to be recalibrated when it's replaced. I'm guessing it wasn't recalibrated and that's the source of your problem - the BCM is confused as to how hard you're pressing on the brake pedal.


----------



## carbon02 (Feb 25, 2011)

m2carb-

Hang in there, there are several members of the forum with shop manuals. I may actually be at a local library that has alldata this weekend, if so I will look.

From my understanding of the theory with the supplementary pump.

Is this a manual transmission? If so maybe the problem is mechanical, as they never felt the need to fix the effected cars with manual transmissions for the micro-switch issue. I believe the it was studied that the auxillary pump wasn't needed with the manual transmission. That's the reason why those cars were not included with the recall. So if you're having problems I'd look more into the mechanical aspects of the power brakes.

Now assuming it is AT. With car parked in a safe open area. Engine off.. Pump brake pedal to deplete master cylinder brake booster.. Pedal hard. Now key to ON... NOT start.. You should clearly hear the auxiliary brake pump run. If it doesn't then there's a problem with the microswitch, or the pump.

The question becomes are they taking the microswitch into the BCM and doing some logic to then fire an output to the air pump? I'm not in front of a car, but the pump is located fairly low on the drivers inner fender. I would consider removing one of the hoses from that pump if possible and looking for water.

Yes it would be great to have the electrical schematics handy, and they may or may not be a quick find, but I'm guessing a flood car, if the water got to the bottom of the rocker panels this pump could have ingested water. 

I also thought that the pump was only necessary when the engine was under heavy boost, making the intake manifold under pressure. Light throttle conditions should make the car pull vacuum naturally having brakes. Anything you can add about when this happens would be a benefit.


----------



## m2carb (Sep 11, 2015)

Ok, thanks! It is an AT. My son reports it has intermittent issues when trying to stop, go from park into reverse or park to drive, and the pedal gets really hard to push. For instance, park to reverse, backing up then applying the brakes, pedal hard, coming up to a red light, not stepping on the gas, pedal hard. Seems like under not much load is when the issue happens. I have not experienced it myself, only what he tells me.


----------



## Blue_RS (Aug 30, 2013)

This happened to me twice on my 2012 i had. The second time it burnt out the electric assist vacuum pump.


----------



## Chevy Customer Care (Oct 29, 2011)

m2carb said:


> Ok, thanks! It is an AT. My son reports it has intermittent issues when trying to stop, go from park into reverse or park to drive, and the pedal gets really hard to push. For instance, park to reverse, backing up then applying the brakes, pedal hard, coming up to a red light, not stepping on the gas, pedal hard. Seems like under not much load is when the issue happens. I have not experienced it myself, only what he tells me.


Hi M2carb, 

We appreciate you bringing this to the attention of the community as well as ourselves. If you son decides to bring this to the dealership's attention, feel free to send us a private message along with his info. We would be more than happy to assist the best way possible! 

Patsy G
Chevrolet Customer Care


----------



## Robby (Mar 1, 2013)

There is no relationship between the brake light switch and the booster pump switch.

You can see the two wire connector plugged into the switch inline with the vacuum hose leading into the booster unit.
Unplug the connector and jump the leads with a cotter pin…..key on engine off….you should hear the pump run.
If it does, the switch has failed…..if it does not run, check for power at one of the terminals….if you have power, odds are the pump was immersed and has died.

Rob


----------



## NickD (Dec 10, 2011)

All vehicles equipped with a turbo require this switch and a vacuum pump. Reason, vacuum comes from the intake manifold and can vary from 20"/Hg up to 35 psi positive boost pressure. 

But if you take your foot off the gas, TB vane will close, engine is still revved driven by the drivetrain, and you will get lots of vacuum. Really only way to get positive pressure is to hit the gas in turbo boost and hit the brake at the same time, not a good idea. 

Vacuum booster has a check valve in it so air can only flow out, they can hang up occasionally loosing its vacuum. Even with the car sitting overnight without starting the engine, should have a soft pedal three times with the ignition keys in your pocket. If not, booster has a vacuum leak. Vacuum switch is also like a check valve, if it see positive pressure will close off the manifold vacuum, close the switch and activate the vacuum pump connecting the booster to the pump. This can also leak and easy enough to test. Typically about 20 times or more to lean if it skips a beat. Can do this on the bench with a vacuum pump, even a vacuum cleaner. 

Sure buried the vacuum booster in this thing, battery, coolant reservoir, vacuum pump, ABS module is all in the way. Coolant reservoir snaps in so nicely when you put it in, but try to remove it without breaking something.


----------



## m2carb (Sep 11, 2015)

Good afternoon, today is the first chance I had to check this since my last posting, fighting pneumonia right now, no fun. 

Anyhow, pushed the brake pedal after the car sat for hours, got three pumps with vacuum until the pedal firmed up, look
s like the engine vacuum portion is working as when we started the car, we had a soft pedal again. Shut the car off and bled of the vacuum, turned the key to on, no sound from the vacuum pump. 

Pulled the connector from the switch on the vacuum boost, it is three wires, not two, I would like to measure voltage and try jumping the pump wires to see if it will run without the switch on the boost, but I am unsure now which wires do what, does anyone know the pin out for this connector? It is a purple colored one on a switch which goes right into the left hand front side of the booster as you face the firewall.

Hoping to get there soon, thanks everyone!
Chris L.


----------



## Robby (Mar 1, 2013)

Two wires on my 2012 eco automatic: Red with a white tracer……and Tan…..both going into a brown connector attached to the switch inline with the vacuum booster hose.

I watched the dealer replace boatloads of these switches during the recall…..all use the same, two terminal switch.

Rob

Going to need input from a 2013 owner.


----------



## NickD (Dec 10, 2011)

You won't get any vacuum just by turning on the ignition switch to run position, vacuum switch is not seeing any positive pressure from the intake manifold. So the vacuum pump will not switch on. Have to start the engine.

Could be the engine itself, the source of this vacuum, ha, so much easier for me to test stuff like this than to type it. Would hook up a vacuum gauge to the intake manifold, at idle, should read 20"/Hg minus 1" for each thousand feet above sea level. Possible an intake valve is not fully closing, this would kill manifold vacuum in a hurry. Next step would be to do a compression check expecting to see 150 psi on each cylinder.

Bit of carbon on an intake valve causes severe leaks, a can of SeaFoam could cure this. Revving the engine does drop the vacuum as the TB valve is wide open, but should snap back the instant you are back at idle.

Can't do this by yourself in the Cruze, need an assistant to hit the gas pedal with this throttle by wire.


----------



## jblackburn (Apr 14, 2012)

Vacuum pump should trigger with the ignition on and engine off while pumping the brake pedal. When you drain the vacuum from the booster, that switch should close and run the pump.

Unfortunately I am a 2012 manual, so probably the 2 wire design as well. I will check later tonight.


----------



## ChevyGuy (Dec 13, 2014)

According to my 2013 manual, the sensor is a pressure sensor, not a switch. It has 5V and ground and sends back a voltage proportional to the pressure. (Wire color "YE/RD")

The sensor is connected to the brake control module, which controls a relay (KR14) that runs the vacuum pump.

It seems like this problem should set a code. Any way to scan for codes from the brake system?


----------



## m2carb (Sep 11, 2015)

I really wish I had a wiring diagram for this circuit. Usually a relay is on or off, not sure how this works if the voltage to the brake control module is proportional to the vacuum or positive pressure at the pressure sensor. Not sure if someone is willing to share at least the portion on the vacuum pump circuit from a GM service manual. The first picture shows the brake booster, second the connector unplugged, third the switch (or sensor) with the wire connector unplugged, 4th, what I believe is the vacuum pump buried in the picture. Posted these pictures to make sure I am at the right place. Hoping to figure this out, my son took it into the dealer for the three recalls on the 2013 Cruze, and they mentioned the vacuum boost having an issue, but he does not have $500+ to have the dealer fix it.


----------



## carbon02 (Feb 25, 2011)

M2Carb-

Early versions of the cruze had pressure switches with just two wires, I'm suspecting just a discrete contact closure to the Brake Control Module that would then fire an output to close the relay energizing the auxiliary pump. I'm guessing that after the thousands of switches that were replaced under the recalls of the earlier versions, engineering went to some type of variable voltage output from the "pressure sensor" to the Brake Control Module. Guessing this voltage signal is visible using GM tools, or maybe even written in memory for liability/legality reasons.

From previous experiences with brake control modules this is a computer type module that probably can fire an output to the relay. And a code tool like Torque on the Android market can not read any codes that would be in the Brake Control Module. Older 2000 GM Control modules were located at the bottom of the junction where all the individual brake lines separate off. This also drives portions of the control of the ABS system. (EBCM I think GM uses.) 

The aux booster pump can be found by following the black 1/2 vacuum line from the "y" in near the brake booster. You're in the right location. It's buried down there. 

Disconnecting at this location and back probing the connector to the pump for 12 volts from the brake control module would be something that you could look for. Having to trace both sides of the relay for voltage as well. I'm guessing this relay is in the box next to the battery.

Yea it would be nice to have pin locations and everything identified. You can buy a subscription to alldata homeowners edition for $30/year per vehicle. However, I'll warn you now, finding the actual circuit diagrams and following them takes a lot more time than the old paper manuals. 

I'd see if you can investigate further down in the area near the pump for signs of corrosion.


----------



## ChevyGuy (Dec 13, 2014)

carbon02 said:


> I'm guessing that after the thousands of switches that were replaced under the recalls of the earlier versions, engineering went to some type of variable voltage output from the "pressure sensor" to the Brake Control Module.


Exactly what I was thinking. That way the system can detect a failed sensor as well has have the "switch point" changed by a software re-flash.

Now, why they didn't add a test to see if the vacuum pump had an effect on the pressure - I don't know.


----------



## NickD (Dec 10, 2011)

Did you ever check your intake manifold vacuum? Dealers can really make the wrong calls.

How about your brake pedal going clear to the floor is not your problem, we ain't getting any codes. 

If your vacuum booster is holding pressure overnight, more than likely not your problem. You did say you were getting assist three times hitting the brake pedal with the engine off.

Only reason for that vacuum switch and the vacuum motor is because the 1.4L has a turbo that changes manifold pressure from around 20"/Hg vacuum to up to a positive 35 psi when the turbo is running.

That vacuum is switch is also a valve, switches the vacuum booster from the intake manifold to the vacuum pump. Is possible this valve if flooded is sticking. Ha, I don't replace valves like this, I clean them. Evaporative vent and idle control valves have the same problem. Test them by blowing into them both activated and closed, if still leaks, then I replace them.

A vacuum booster runs for 64 bucks.










To save 440 bucks, can do this myself, and even to it right.


----------



## m2carb (Sep 11, 2015)

Good morning group,

Lots of things to check this weekend, need to get it up on a lift, I have a friend who has one, will make getting to the connector on the vacuum pump a lot easier. NickD, the brake booster does hold pressure overnight and with the car off, we can get 2-3 pedal pumps with the pedal being soft, before the pedal gets firm. The brake pedal never goes completely to the floor. Thanks to all for the help up to now, we appreciate it! Got to love the internet and folks helping folks, not sure how we got by when I was a kid without it! :smile:


----------



## KENSTV123 (Sep 21, 2014)

I also have the 2013 manuals, I'll have a look and see about the 3 wire and any troubleshooting


----------



## NickD (Dec 10, 2011)

Did I get screwed, 2012 only has two wires on the vacuum switch, normally open contacts that complete the 12V circuit to the high side of the vacuum pump. Not sure at what manifold pressure it switches over at, but guessing below about 6"/Hg that is was my Supra uses.

Two wires does the job, one to 12V other to the vacuum motor that is grounded, really don't need circuit diagram for this, but got me guessing what the 3rd wire is for. Must have a SPDT switch, if so that 3rd wire will have 12V on it when the switch is deactivated.

Let's see what the guys with 2013 shop manuals have to say, but may take them two years to find it.


----------



## ChevyGuy (Dec 13, 2014)

NickD said:


> Let's see what the guys with 2013 shop manuals have to say, but may take them two years to find it.


Already posted. It's a pressure sensor (power, ground, output) that feeds the brake computer, which in turn controls the relay that runs the pump.

Now, it seems like many failures tend to happen on the "power" side of things. So I'm inclined to pull the relay and jumper it and see if the pump works. If it does, then I'd swap the relay. If the problem persists, then the real troubleshooting needs to begin. But I'd give those two steps a 80% chance of working.


----------



## m2carb (Sep 11, 2015)

Good morning everyone!

Sorry I have not posted for a while, and thanks to all who responded. The problem ended up being the vacuum pump itself, replaced it and the brakes are working fine now. I appreciate all of the help we received here, the internet is a wonderful place to get information! And going into winter, my son is happy his car brakes are working as they should!


----------



## NickD (Dec 10, 2011)

Did you apply 12V to the old vacuum pump? Was the motor opened or short circuited. Does have screws on it, would be interesting to learn what was wrong with it. Just a cheap permanent magnet motor running a blower wheel with a 160 buck best price I can find price tag. 

Looks like the same exact motor used in my 2012. On my Cruze with the brake pedal going clear to the floor and a very paranoid service manager calling the experts at GM if he changed the part, would come out of his pocket. They advised him to replace the vacuum switch, vacuum motor, vacuum booster, and the master cylinder that never took care of this brake floor problem. Kept on insisting was not having problems with power assist, the rear disc calipers were shot.

But I guess he got paid for replacing all this stuff, finally after a battle replaced those defective rear calipers, and this solved the problem. We hardly use the turbo, you don't average 40 mpg if you do. But every time you hit the gas, that turbo switches on running this vacuum pump.

Would be fun to see why yours failed, a poor soldering connection? Is the motor seized? Worn brush?


----------



## m2carb (Sep 11, 2015)

NickD, the motor was seized, this was a flood recovery car so I am thinking the pump had a bath, then corrosion got to it after a while. The place my son got the car from got a brand new pump for us, and got the old one back so I cannot take apart to see exactly what took place. But the car's brakes work great now!


----------



## NickD (Dec 10, 2011)

What about this thing then?









Uses bronze bearings and a cold roll steel armature shaft that can also seize like your vacuum motor. Pardon my language, can't help it, but the basterds are hot stamping that blower wheel on now, can't use a nut or even a palnut to hold it on. Got rid of the two screws a long time ago, but could drill out the spot welds and use screws to hold it together.

But no way to remove that blower motor wheel without breaking it, so forced to buy a whole new motor for around 90 bucks plus shipping and sales tax. Only lubrication is a piece of felt with a few drops of oil in it. And zero oil filler tubes on it, no way to lubricate this thing.

Ha, purchased a 15 buck 20" fan from Walmart, least that cheap motor has a couple of oil tubes in it to keep it going. This on the part of GM is nothing short of criminal.

Not sure about this thing either.










So called blower motor resistor, but actually a power MOSFET transistor that is switched on and off for so-called pulse width modulation, also used for years. But the problem with it, it will blow before the fuse does if the blower motor stalls for any reason. And these ran 250 bucks to replace, plus replacing the blower motor as well.

But being handy, could repair this module and used a 22 cent transistor instead of a 14 cent one, so the fuse would blow before the transistor did. Not sure if they are doing this in the Cruze. But at least the replacement one is only 37 bucks now.

The way cars are designed today, can't even drive them without a good working blower motor. 

If I go back to my 70 Buick, blower wheel had a nut on it, and the case halves had screws that held unto the base plate that varied from vehicle to vehicle, not integrated. So all you had to do was to pay 6 bucks at any dealer and get a brand new motor. But why pay six bucks when just the bearings and the brushes could be replaced to make the motor like new again, and that only cost 45 cents.

Another thing with these older motors, the field poles pieces had to be machined with magnet wire wrapped around them, this was expensive. Then they figured out how to mix iron filings with ceramic to make super cheap molded permanent magnet pole pieces, but yet the price of these super cheap blower motors skyrocketed. 

Not good knowing how things use to be.


----------



## krysek (Jun 1, 2018)

NickD said:


> Looks like the same exact motor used in my 2012. On my Cruze with the brake pedal going clear to the floor and a very paranoid service manager calling the experts at GM if he changed the part, would come out of his pocket. They advised him to replace the vacuum switch, vacuum motor, vacuum booster, and the master cylinder that never took care of this brake floor problem. Kept on insisting was not having problems with power assist, the rear disc calipers were shot.


This post is old now but I do have this issue on my 2011 Cruze LTZ. 65k
The problem started just after replacing rear caliper. They are rebuilds. Usually the pedal goes down at the morning. After short driving the pedal is ok however sometimes the brakes are very soft.
Do you suggest I should replace them again ?
Calipers are not identical but they fit perfect. One bleeder has different size.
There reason I have replaced rear calipers was that rotors were not "shine". I have replaced first the rotors and pads and after while rotors become not "flat". After replacing calipers and pads and rotors again, they look good but the pedal is soft.
My mechanic thought that the problem could be the master cylinder but we could not untie two holding nuts. The whole assembly turns with the nuts.


----------



## Blasirl (Mar 31, 2015)

krysek said:


> This post is old now but I do have this issue on my 2011 Cruze LTZ. 65k
> The problem started just after replacing rear caliper. They are rebuilds. Usually the pedal goes down at the morning. After short driving the pedal is ok however sometimes the brakes are very soft.
> Do you suggest I should replace them again ?
> Calipers are not identical but they fit perfect. One bleeder has different size.
> ...



I do believe that Nick is no longer with us. I think you would get a better response if you start a new thread of your own in Gen I Service Issues.


----------



## Bobbycrabtreee (6 mo ago)

m2carb said:


> Ok, thanks! It is an AT. My son reports it has intermittent issues when trying to stop, go from park into reverse or park to drive, and the pedal gets really hard to push. For instance, park to reverse, backing up then applying the brakes, pedal hard, coming up to a red light, not stepping on the gas, pedal hard. Seems like under not much load is when the issue happens. I have not experienced it myself, only what he tells me.


I’m having this problem right now with my 2013 Chevy Cruze and when I put the engine tester on it it says large vacuum leak in break booster so do you think it’s just the vaccum hose ? Or what was your problem


----------

