re: Air mass sensor, '91 200q 20v 3B question...

[C1J1Miller@aol.com]

I think I may have found the problem with my car; going through diagnostics
in Bently indicates:  (page 24-160-3)
under Sensor Function, Checking, about 1/2 way down.

...
[] peel back rubber boot on back of harness connector to expose terminals.
[]  switch multimeter to 20 V range
[]  connect multimeter between (exposed but connected) terminals 1 and 3
[]  switch ON ignition
      ()  must be 1.2 to 2.5 volts.   <nope!>
[]  start engine and let idle
     ()  must be approximately 2.5 volts  <nope!>
[]  Briefly raise engine speed
    ()  voltage must increase to approximately 3 to 5 volts.  <again, no
voltage>
If the specified voltages are NOT obtained, replace air mass sensor.
=================
On my air mass sensor, terminals 1, 2, and 3 are grounded; no voltage, and
continuity to the engine block, ignition off, on, or with the engine running.
 The check engine light goes on after several seconds, and disconnecting the
air mass sensor connector has no effect on engine performance.

Could someone check their car to see if I should have voltage at the
connector, meaning that I have a short to ground in the harness, or if it
seems to be an internal fault in the air mass sensor?  Has anyone replaced
theirs, and have approximate $$?  Is this a part to buy through the dealer
only, or can it be purchased through a Bosch shop for less?

Lastly, diagnostics in Bently talk about checking for continuity between test
box terminals on the motronic harness using an adaptor cable, and the air
mass sensor harness.  Can I disconnect the motronic and test without fear of
cooking the unit?  I assume ignition off the entire time I'm dealing with the
motronic, and properly grounding myself as per any computer work...

Thanks in advance, Chris Miller, Windham NH, c1j1miller@aol.com
I'll be fixing that driver's door lock once the car is not in "limp home"
mode....