Knock Ignition / O2 sensor Theory (VR6 but applies)

[brianm@earendel.org (brianm@earendel.org)]

http://www.ffp-motorsport.com/tuning/vr6tech.php

Volkswagen of America, Inc.

Printed in U.S.A.
Printed 12/91
Part # WSP 521-402-00

All rights reserved.  All information contained
in this manual is based on the latest product
information available at the time of printing.
The right is reserved to make changes at any
time without notice.

Always check Technical Bulletins and the mirofiche
system for information that may supersede any
information included in this manual.

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*** Knock Sensor I (G61) And Knock Sensor II (G66) ***

Two knock sensors are used.  A knock sensor works like a microphone to 
"listen" for spark knock or detonation.

When knocking occurs, the ignition timing is retarded until the knocking
is eliminated.  Since the knock limit differs from cylinder to cylinder 
and changes within the operating range, knock regulation is done
cylinder
selectively.


* Signal usage: *

Knock regulation does not occur until the engine coolant temperature of 
40 C (104 F) is reached.  Knock sensor I (G61) monitors cylinders 1,
2,
and 3.  Knock sensor II (G66) monitors cylinder s 4, 5 and 6.

With the aid of the Hall sender signal, the ECU can determine which 
cylinder is knocking.  The ignition angle of the knocking cylinder is 
retarded in steps until the knocking stops up to a maximum of 12.

If spark knock is still detected, the ECU will retard the ignition 
timing 11 for all cylinders and record a fault.

* Substitute function: *

If a knock sensor fails, the ignition timing angle of its assigned 
cylinders is retarded.

* Self-diagnosis: *

The ECU recognized an open circuit if no signal from knock sensor I
(G61) or knock sensor II (G66) is received by the ECU at an engine coolant
temperature above 40 C (104 F).


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*** Oxygen Sensor (G39) ***

The oxygen sensor (G39) is made of a ceramic material called zirconium
dioxide.  The inner and outer surfaces of the ceramic material are 
coated with platinum.  The outer platinum surface is exposed to the 
exhaust gas, while the inner surface is exposed to the outside air.

The difference in the amount of oxygen contacting the inner and outer 
surfaces of the oxygen sensor creates a pressure differential which 
results in a small voltage signal in the range of 100 to 1000 mV.  
The amount of voltage that is produced is determined by the fuel
mixture.

The oxygen sensor (G39) is heated electrically to keep it at constant 
operating temperature.  The heater also ensures that the sensor comes 
to operating temperature quickly.

The sensor has four wires.  Two are for the heating element (ground and 
power).  One wire is a signal wire for the sensor and one for the
ground.

* Signal usage: *

The base injection time is corrected according to the voltage signal 
from the oxygen sensor to maintain a fuel/air ratio of approximately
14.7:1. This allows the three-way catalytic converter to operate at its 
maximum efficiency.

If the fuel mixture is lean (excess oxygen), the oxygen sensor will send 
a low voltage signal (about 100mV) to the ECU.

If the fuel mixture is rich (lack of oxygen), the oxygen sensor will
send a voltage signal (about 900 mV) to the ECU.

* Substitute function: *

There is no substitute function for oxygen sensor (G39).  If signal
fails, no oxygen sensor regulation takes place.

* Self-diagnosis: *

The ECU recognizes a fault if no reasonable signal voltage range is 
attained within five minutes after engine start with an engine coolant 
temperature over 40 C (104 F).

The ECU also recognizes a open circuit in the wiring or a short circuit 
to ground andshort circuit to positive (sensor heating).