Actron CP9087 - Manual (Page 34)

2-26
Testing Sensors
Section 2
What to
Inspect
Sensor operation (see test on page 2-27). Poor
connections at sensor or computer. Faulty sensor
wiring (open or short circuits). Spark timing. Bad
fuel quality.
When to Test
• Related trouble codes sent by computer.
• Knocking during cruise or hard acceleration (not
enough spark retard), hesitation, poor perfor-
mance and fuel economy (excess spark retard).
Location
Usually threaded into (or bolted on) the engine
block, intake manifold or exhaust manifold. Often
near the cylinder heads.
How it is
used?
The computer (or other spark timing controller) is
designed to recognize sensor signals caused by
engine knock vibrations. Then, spark timing is
retarded to eliminate the damaging knock condition
What is It?
The knock sensor is a piece of piezoelectric
material mounted in a metal housing. The sensor
acts like a microphone - it changes vibrations into a
small AC voltage signal. The sensor usually has a
one wire or two wire connector.
Yellow
Black
Yellow
Black