[200q20v] Re: Throttle Switch/Potentionmeter -Reporting Back

C1J1Miller at aol.com C1J1Miller at aol.com
Thu Nov 16 13:18:50 EST 2000

In a message dated Thu, 16 Nov 2000 12:53:13 PM Eastern Standard Time, 
Calliope <calliope3 at starpower.net> writes:

<< Chris, I took the day off to work this, so I am sending this from home
and not to the list. If you would like to forward this to the list,
please do, my home email is callope3 at starpower.net.

I'm forwarding my reply to the list.  BTW, you can post to the list from any 

I have completed all the tests indicated in the Bentley and on the SJM

The idle switch appears to be fine. You can hear it click, and it passes
the open/closed throttle resistance checks.

On the potentiometer, resistance is fine in all conditions, conforming
with the Bently and directly in line with the values on SJM page.

However, it fails the reference voltage test in the Bentley, 24-130 -1
Pins 1 to 2 show 5v, but pins 1 to 3 only show 3.28v instead of 5. I
interpret that to mean that there is continuity, but low voltage.

It also fails the (different) voltage test on Scott's page, where you
read the voltage between pins 2 and 3, with the ignition on. Here I get
a steady 1.0 volt, regardless of the throttle postion, instead of his
numbers, ~.2 closed and ~4.6 open. (Interesting that Scott talks about
pulling back the rubber boot to do this test, my fittings are all stock
plastic, no rubber. I presume this test is to be done like the others,
with the ignition on and measuring the voltage at the disconnected
connector. I was a little confused when he talked about pulling back the
rubber boot, I just have hard plastic connectors.)

I haven't taken the time to re-read Scott's page, but I believe what he wants 
you to do is to keep the connector attached.  By "pulling back the rubber 
boot" I think he means to pull the rubber boot at the back of the connector, 
so you can use fine probes to read the current without pulling off the 

Cheap ascii:

=(wire)==========[:|:](throttle switch)

                 tap readings off wire here

The next step in the Bentley requires connecting a test unit and adapter
cable to check the voltages out of the Motronic control unit, and if
incorrect replace it. (Please tell me it ain't so...).  Of course,
without some adapter, even with Scotts pin out info, I can't measure
anything at the ECU.

I think the adaptor may be allowing you to read voltages without damaging the 
ECU pins on the connector.

Incidently, driving home last night I found that boost is reduced,
another indication of potentiometer problems: I could only pull 1.9 bar,
instead of my usual 2.4. No whistle or leaking sounds, either.

Your thoughts? Anyone else have any ideas?


Tom Forhan
Takoma Park MD, near Washington DC

I'm still not sure how you're reading 2.4 bar on a stock gauge... the 200q20v 
gauge is supposed to only read up to 2.0 bar (and above that, still reads 
2.0).  Stock boost is only 1.8; typical mods change the pressure transducer 
and allow up to 2.4 bar max, but the changed pressure transducer usually 
means the stock gauge reads low.  Who did the chip?

Also, how's your crankcase breather hose setup, and control valve?

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