Brake Boost Vacuum System: Mechanical Failure -P1479

[Auddii]

Hi guys,

I'm pretty new here. I own a 2001.5 A4 1.8t.

I'm posting in the b6 section since my cars 1.8t is more related to a b6 anyway. Most b5's don't have the same brake booster system.

I've been having issues with my car, I've been getting low vacuum and generally running like crap pointing to a vac leak. I have pressure tested the system and haven't found anything so my next step will be to get my car smoke tested.

As the title suggests I have been getting this code.
17887 - Brake Boost Vacuum System: Mechanical Failure
P1479 - 35-00 - -


So what exactly is this telling me? How do I test the brake booster and could it be the source of my leak?

Any help would be fantastic. I'm just wondering exactly what this code means.

Thanks

[MikTip]

Are you going to DIY repair your Audi?

Or take it to a shop?

[MikeWire]

The brake boost vacuum is the small silver cylinder behind the drivers headlight housing - it supplies extra vacuum to the brake booster, and is only found in the automatic transmission models.

There's a vac line tube that comes out of the bottom and connects to the lines running up to the brake booster. Either the pump is not working, broken, or the line is split or broken. There's an output test using VCDS (vag-com) if you have it available (sounds like you do...) - open the engine module and click on output test until you reach the test for the brake booster vac. Then you'll have a good idea of the problem.

[texasboy21]

The brake boost vacuum is the small silver cylinder behind the drivers headlight housing - it supplies extra vacuum to the brake booster, and is only found in the automatic transmission models.

There's a vac line tube that comes out of the bottom and connects to the lines running up to the brake booster. Either the pump is not working, broken, or the line is split or broken. There's an output test using VCDS (vag-com) if you have it available (sounds like you do...) - open the engine module and click on output test until you reach the test for the brake booster vac. Then you'll have a good idea of the problem.

This

Additionally, a bad fuse can cause this problem.

http://wiki.ross-tech.com/wiki/index...7/P1479/005241

[diagnosticator]

A faulty vac pump, or a leak in the hose/tubing or a bad booster vac supply check valve, or a bad brake booster are all possible causes for the 17887 DTC stored. Using VCDS, check the measuring block 008 in the Engine ECU. MB 008 shows the brake booster vacuum pressure in milliBar. Record the value shown with the engine turned OFF, and with the enging idling and with the engine idling and the brake pedal pressed to apply the brakes. Post back those values.

[mikees501]

I also have a P1479 issue and an 8 month old steady rough idle. The pedal test produced 360mbar “OFF”, 315mbar “IDLING” and 360mbar w/engine running. Vacuum Pump test resulted in a “System Not Ok” and 780mbar. The Pump has been benched and works fine. I have plenty of brake and it certainly does not feel as though the booster or the pump is at fault. Still smells like a vac/boost leak but I’m not clever enough to find it.
Thanks for the forum and I plan to stay with it until it’s fixed or one of us dies. 

[a420]

Have you removed the battery cover and checked the vac. line and the 90* fitting going into the booster? I had that fitting break on me and it gave me the same code.

Good luck.

[mikees501]

Thank you for the heads up. I've literally spent the last 8 months (off and on) disecting and testing every inch of my B6. DV, BOV, PCV, check valves... you name it and I've either replaced it or swapped it out with a known good unit. Made all the PVC fittings for boost testing etc. I evidently need another set of eyes :-) I will eventually WIN.

[preluding]

Subscribed...
I have the same issue. No engine light on but brake pedal is hard to press when engine first come on. (03 A4 1.8T Automatic)

[tehbry]

Would this fuse be in the main fuse panel box by the drivers door?

[DoubleATO]

does anyone know where/how to get an exact replacement of the hoses and elbows going from the brake boost vacuum to the brake booster on an automatic. I cant seem to find anything

[alimo20]

Ive been battling this issue for some time now. replaced all PCV components with the exception of 2 check valves. Boost leak tested, no leaks. I get the following values for the brakes:
- Engine ON, Foot Off - 305mbar
- Engine ON, Foot On - spike to 400mbar then drops and holds to 305mbar
- Engine OFF, Foot Off - 985 mBar
- Engine OFF, Foot On - 1000mBar

Note that the values for engine off are from when the engine was warmed up already.

Didn't check my MAF yet however. I am also getting a lean code for some time.

[jdog6973]

When you run the test with VCDS should the vacuum pump status ever be pump on?

[JAudi23]

When you run the test with VCDS should the vacuum pump status ever be pump on?

Yes, I just did this tonight, the part of the test where you press down firmly on the brake pedal, that's when the pump will kick in. (Pump On)

[EuroxS4]

Check for water in the line and in the booster. Also isnt there supposed to be a check valve on the hose going to the booster. make sure that installed the right way.

[JAudi23]

Even though this is an old thread, I am posting these photos showing what I found in my failed pump after replacing it with a junkyard pull that was working.
I got the same codes as the OP did, and it kept blowing fuses.
This was my original after disassembling it.

20200222_230734.jpeg 20200222_230724.jpeg

20200222_231045.jpeg