Problem ABS pump unit

[iqbad]

Hi,

I bought an audi A3 -96 recently that had the ABS warning light on. I thought that it was probably an easy fault, maybe a broken sensor or something. However, now I have investigated a little bit more and it seems like I have a problem with the ABS pump unit.

I connected wbh-diag tool with my USB-ODBII cable and pulled the code for the ABS controller. Code was "01276 - 16". Searching Ross-tech gave the following description:

01276 - ABS Hydraulic Pump (V64): Signal outside specifications

One common fault for this code on several VWs seems to be bad connection to the fuses above the battery or the ground ground point to chassis. I have checked this and measured all the pins in the connector to the ABS control unit.

Supply has stable 12,7V on both lines. Also supply from 5Amp fuse from fuse box inside car shows correct voltage when key is in right position. All wheel sensors show about 1kOhm when measuring from the pins in the connector. The hydraulic pump itself shows 1,2Ohm. It not not possible to delete
the error code.

Questions:

1. Is 1,2 ohm a normal value for the hydraulic pump motor? I have searched the net now for days without finding anything. Could someone help me by measuring their pump? It only takes about 10 minutes to do it.

2. It does not seem that wbh-diag can do the same test as Vag-com. Is there any other free tool that can test the hydraulic pump?

3. Has anyone taken one of these pumps away from valve block? Is it possible to do so without having oil leakage? Would it be possible to change the motor without having to bleed the brakes?

4. Does anyone have a picture how the pump/motor looks like when it is taken away from the valve block? What does the connection look like? Maybe someone has a old broken one which can be dismantled and photographed?

5. Would it be possible to bleed the brakes without VAG-com?

6. Does anyone know how the ABS control unit tests the pump? Is it only a resistance measurement, or something else?

7. Any other tips?

Regards, Eric

 

[S3KO4]

from what I have heard, you will need a full VAG com to get the system bleeding.. as another mate is in the same situation.

 

[AndyMac]

ABS control module fault would be a more likely suspect wouldn't it? If it's a Bosch unit then they are inherrently unreliable especially on the B5's. On the upside you can remove it without touching the pump, so not bleeding and you can drive the car while it's being repaired (at least this is the case for the B5)

 

[iqbad]

Thanks for the replies so far. The system is made by ATE and I think it will be hard to remove the electronic part without removing the pipes. I have now ordered a used replacement from a junk-yard. It will hopefully get here in a couple of days. I will the try to see it it is possible to change the pump without bleeding. If I get the error code away I can try also to check what an approved value for the pump resistance is. I will check if there is a possibility to bleed without vag-com. I do have an M.Sc in hydraulics, so I'm not giving up till I fix this!

 

[thegoal007]

If I'm not mistaken it's not straight forward at all to seperate the pump with the electronics. If you are going to do it - replace the whole thing - job done.

 

[AndyMac]

I did say "if it's a Bosch unit" sorry my mistake! the whole point of just replacing the module is that you then don't have to touch the hydraulics, 30min jobs vs 3-4 hour job.

 

[iqbad]

I did say "if it's a Bosch unit" sorry my mistake! the whole point of just replacing the module is that you then don't have to touch the hydraulics, 30min jobs vs 3-4 hour job.

No worries, I know these cars have a lot o different systems. According to haynes, there are even several models of the ATE unit before they changed to bosch. I will try as long as possible not to get air into the system so if I find out that its doable to remove the electronic part, I will give it a try.

Does anyone know what the Vag-com unit does when it bleeds the pump? Is it only running the pump for a while or does it also open the inlet or bypass valves in some kind of sequence?

I have read that changing the ABS unit might could require to reprogram the new unit somehow, does anyone have more information about this?

Thanks!