PSM/ABS 5.X Gurus... Help?

[jpurban]

Running into some trouble trying to bleed my rear brakes and I've isolated the issue, but don't know how to resolve it.  Hoping someone here more familiar with the PSM module might be able to help.

 

Issue:  I'm using a Motive bleeder and have good flow into the "H" (rear) input port of the ABS block, but I have no flow from either the HL (rear left) or HR (rear right) output ports of the ABS block.

 

I know the PSM system doesn't have a mechanical proportioning valve, but could the system have electronically isolated the rear circuit?  If so, any idea how I might reset it?

 

That could be the wrong track...  maybe I have a bad relay or solenoid.

[Loren]

The system will not bleed the ABS without turning on bleed mode using Durametric or a Porsche PIWIS tool.

 

If you have not opened the system (introduced air) then you should be able to bleed the brakes normally bypassing the ABS/PSM system.

[jpurban]

Loren, thanks for the quick reply.

 

My front circuit bleeds just fine thru the block...  Flow at V, VL, VR as well as both front calipers, but I'm getting nothing from the rear outlets ( HL & HR).  I've removed the input line from port H and verified there is fluid in the ABS block.  Master cylinder was replaced and is now working as it should.  New MC was bench bled before installation along with inlet tubes to minimize any air entering the ABS..

 

MC was replaced because rear circuit wasn't flowing, which might explain why the EBD would have closed the rear circuit (sensed low pressure and closed circuit to protect against a downstream leak).  Seems plausible anyway...  That is why I'm wondering if I need to reset the PSM/ABS to return the "normally open" EV rear outlet valves to their "normally open" state, which would allow me to bleed conventionally (as you suggest).

 

Most of this is pure hypothesis...  Since very little info is available on the Bosch ABS/PSM (I have the workshop/diagnostic manual), I'm left guessing.

 

I have a Durametric, but it doesn't have drive links for individual EV/AV valves -- only the switchover valves.  So, I don't think Durametric will be useful in "resetting" the ABS.

[ealltech]

My first question for the shop you took it to would be "What type of diagnostic scanner are you using?"  If the answer is not  a PST II, PIWIS, Durametric, or Autologic system, they cannot even see several of the key system that need to be tested.