ECU “output tests”

[Marc Boucher]

I get some inconsistent results when I perform ECU “output tests” and I was looking for some ideas.  I’m using the tests described as “Output Tests 1987-88 5000S, and 1989-91 Audi 100 with CIS-E-III” which is described at this link:

http://www.sjmautotechnik.com/trouble_shooting/100ecuf.html#out2

 

First let me mention that I’ve got 2 ECU’s sets, and the same result occurs with both.  Second, the WOT switch has been verified to be working correctly via ohmmeter.  Same for the idle switch.  During these tests the idle switch is verified to be closed and the WOT is opened and closed to activate the tests. 

 

One of the tests involves pressing the WOT switch and verifying that the Cold Start Valve cycles on and off for 10 seconds.  This test passes exactly as described: when you cycle to that test (via fuse and fuel pump relay), nothing happens until you close the WOT switch.  This isn’t the first test, but I mention it first as further evidence that the WOT switch is working.

 

The other tests results aren’t quite exactly as described:

 

Another test says “Close the full throttle switch again, and the Carbon Canister Solenoid valve is cycled on and off”.  In my case, this valve is cycled on and off as soon as you get to that test, and the WOT switch has no effect.

 

Another test says “Close the full throttle switch and the Idle Stabilizer valve cycles.”   ”.  In my case, this valve is cycled on and off as soon as you get to that test, and the WOT switch has no effect.

 

Finally, another test says, “The Differential Pressure Regulator with have 10 milli amps applied to this regulator when the full throttle switch is manually closed. 100 milli amps when the throttle switch is open”.   My result: a steady 10 milliamps passing through the regulator regardless of whether the WOT is closed or open.

 

Thus the WOT tests appear to have no impact on 3 of the tests.  But on the 4th, it does.  

 

I’ve been doing some repairs on the car and its now driving perfectly.  I've pulled the codes and there are none.  But I’m wondering what could be wrong why the test results are so different from what's described, in particular the Differential Pressure Regulator never getting 100 milliamps.

 

Thanks for any suggestions,

MC