Syd B.

My Anti-lock warning light has been coming on and as I reported previously, my mechanic replaced a failed speed sensor (I incorrectly referred to this before as a wear sensor) and the warning light stopped. This evening, however, the light came on again and this time, when I turned off the engine, a buzzing sound was coming from the ABS control unit in the trunk. Fearing that leaving it buzzing like this would create further damage, I removed fuse #16, however, the unit must receive power elsewhere because the buzzing continued. I have now disconnected the battery.

Anyone know what might be wrong with the ABS unit? (BTW, the brakes still work)

Adrian

Dear Syd,
Please provide more details on your model. The ABS control unit is only fitted to the C2. I want to make sure you do not have a C4 where the answers will be different.
Pull the connector from the ABS control unit and then reconnect the battery. You can drive safely without ABS. The control unit should not buzz but we need to make sure that it is really the control unit. It may be full of water. When you pull the connector check for water in the plug.
Ciao,
Adrian
911C4

Syd B.

Hello Adrian and thanks for responding. Yes, I have a C2. I actually disconnected the abs this morning and didn't notice any water present or wire corrosion.

Adrian

Dear Syd,
The unit is fairly easy to open. I would open it up if you are 100% certain it is buzzing. Please confirm that with the battety connected and the ABS control unit disconnected or removed that the buzzing is gone.
Ciao,
Adrian
911C4

Syd B.

Adrian, yes, the unit stops buzzing with the battery disconnected and starts again when the battery is reconnected. I haven't attempted to open the unit, but I'm certain that the buzzing noise is coming from it. Also, it was very hot to touch before disconnecting. I don't know if this is normal.

John Boggiano

Syd,
Did you misunderstand Adrian, or did I misunderstand you?

With the ABS unit disconnected, but the battery connected - does it buzz or not?

Syd B.

I'm sorry. I did misunderstand. The buzzing stops with the ABS disconnected and the battery connected. Adrian, did I understand you correctly when you said it is OK to drive like this?

Adrian

Dear Syd,
No problem to drive like this. The ABS is hardly used in normal circumstances anyway. Just remember under really hard braking you may lock your wheels up but I am sure you know how to deal with this. Perfectly safe just adjust hard driving accordingly.
The ABS control unit should not get hot and certainly not very hot. Unless the ABS is activated it is not doing much. We must look though at what might be causing the problem. I cannot think of anything internally. However the problem may have been caused by the pump in the ABS hydraulic unit. You will see this assembly at the right rear of the luggage compartment. You have to take off a black cover. You will see on the top of this assembly two relays. They are black. Remove them. The reconnect the ABS control unit and see if the buzzing starts up again.
Ciao,
Adrian
911C4

Syd B.

Adrian, I had actually tried removing the relays before I unplugged the unit. If we are referring to the same thing, they are the ones with the fairly thick pins, one with 4 and the other with, I believe, 6 or 8. The buzzing continued with them out.

I feel much better knowing that the ABS malfunction does not interfere with normal breaking, although I will be attending the shop asap to have this matter assessed. I appreciate your thoughts and will keep you posted as to my mechanic's findings. Please advise, should any further ideas come to you.

Thanks again,

Syd

Adrian

Dear Syd,
I beleive you have found the relays I suggested. I am sure the control unit is fried but what fried it? I would hate another control unit to be plugged in and it is fried as well.
I suspect excessive current draw from the ABS hydraulic pump motor but I cannot be sure.
Ciao,
Adrian
911C4

Syd B.

Adrian, before I head off to the shop to make yet another contribution to my mechanic's retirement fund, do you have any idea what a new ABS control unit is worth? It looks and sounds expensive.

Randall G.

Hi Syd,

Your ABS light going off after hitting a bump sounds similar to my recent problem, the buzzing doesn't. Anyway, have you tried checking/cleaning the ABS control unit's ground connection? As I wrote on another thread, my copper ground connector had oxidized--quite visible.

<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

Syd B.

Actually, Randall, I saw your post and checked the ground wire yesterday. It was indeed, oxidized, however, the buzzing continues. I think its my Porsche telling me not to sell her.

Randall G.

Sorry to hear that the P-car has to go. It's shocking how much insurance is for a 10+ year old 911. You can insure a brand new G35 Coupe for less money, a brand new 'Vette for about the same. Amazing.

Syd B.

Randall, the insurance on the Porsche, although high, is not what is forcing my hand. It the insurance on my 16 year old, who will be treated as a principal driver of one of my cars. That price tag is a killer. If our winters weren't so harsh here, I'd sell the G35 and keep the Porsche in an second. Maybe I'll sell my wife's car when she's not looking.