fuel AUDI A4 1999 B5 / 1.G AFC Engine Cold Start Driveability Problems Workshop Manual

24-44

CAUTION!

Use a second technician to operate the VAG
1551 scan tool.

- Start engine (without previously switching
ignition off), drive and record voltage signal
(display field 3 shows bank 1; display field 4
shows bank 2).

When oxygen sensor control starts, the voltage
signal fluctuates between 0.0 and 0.9 volts (the
voltage signals of both banks do not need to be
synchronous with one another).
If driveability difficulties occur before the start of
oxygen sensor control, oxygen sensor control
can not be the cause of the problem.
If driveability difficulties occur after the start of
oxygen sensor control, check function of heated
oxygen sensor page 24
-45
.

If driveability improves after the start of closed-
loop oxygen sensor control, the cause (e.g. air
leak, faulty fuel injector) works against the
improvement by interrupting control. This can
be recognized by reading the oxygen sensor
learned values Repair Group 01, "Read
Measuring Value Block" function 08, display
Pa
ge 3 of 4 Cold start driveabilit
y problems, overview
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