Vag - Com Scanning: 1991 200 20V

Can you help us trouble shoot this car?

John has a hesitation:

"Check eng light is OK.

If I disconnect the ecu and plug it back in the light comes on for a sec.

Had a Vag-com on it last week (thanks Scott from Boston) and

it pulled codes just a couple times out of about 20 times.

I managed to get a 2231 code out of it the other day but can't pull any more codes.

Car has a stumble at 3500-5000 rpm. In boost, out of boost, hot, cold.

All sensors check out. Do I have a bad ECU?"


I was able to communicate and pull codes (No DTC's) it said:

with Vag-Com a few times.  I'd get the "Motor" controller:

Most other times there was "no response from controller."

Hex-Com connector would go green, yellow, green, yellow then "no response"

If the data or controller was logged/read, it would blink red-ish then display data.


Full-scan of the car would produce no DTC's (fault codes)

although the menu said "may not be communicating with controller....."


I could occasionally, by restarting Vag-Com - version 303.1

or his unplugging and reconnecting the ECU harness, get these measuring blocks to work:

Don't worry, power (by key) & Vag-Com was disconnected each ECU connect.

Block 1 is temp

Block 2: okay  Block 3 RPM?  Okay.

Block 3,4,5,6 all were 1/2 the 120 or so value Bentley lists.  This points towards ISV & related.

Blocks 8 & 9 are O2.  Again these values were supposed to be 120 or so.

Block 10 supposed to be between 35 & 37.  OKAY.

Additional info:
Vag-Com on really old Laptop with super slow, like Audi likes, baud rate.
Offical 2x2 ugly cable. Hex-Com
able to pull codes and monitor Engine Channel 1, measuring blocks at: "000" occassionally.

Worked well as a test on another 200 20v in the driveway.

Codes (extrapolated data from Engine 1 as the Vag-Com could talk to the

"controller"/"motor", but wouldn't register a fault code (DTC)).

Channel "000" were O2 sensor readings flat & steady low 15 & 7 in fields/channels 8 & 9
and channels 4,5,6 were 1/2 the 120 or so value they needed to be 57. 60 -ish.

this leads towards the ISV (air leak). He checked this and carb cleaned the ISV valve.
Check the Bentley Volume 1, reference tables in trouble shooting,

in the back: D2-Page 440 for chart for above fields of data.


Car runs and drives except for the hesitation described above.