KNOCK SENSOR
DESCRIPTION
The knock sensor threads into the cylinder block.
The knock sensor is designed to detect engine vibra-
tion that is caused by detonation.
OPERATION
When the knock sensor detects a knock in one of
the cylinders, it sends an input signal to the PCM. In
response, the PCM retards ignition timing for all cyl-
inders by a scheduled amount.
Knock sensors contain a piezoelectric material
which constantly vibrates and sends an input voltage
(signal) to the PCM while the engine operates. As the
intensity of the crystal’s vibration increases, the
knock sensor output voltage also increases.
The voltage signal produced by the knock sensor
increases with the amplitude of vibration. The PCM
receives as an input the knock sensor voltage signal.
If the signal rises above a predetermined level, the
PCM will store that value in memory and retard
ignition timing to reduce engine knock. If the knock
sensor voltage exceeds a preset value, the PCM
retards ignition timing for all cylinders. It is not a
selective cylinder retard.
The PCM ignores knock sensor input during engine
idle conditions. Once the engine speed exceeds a
specified value, knock retard is allowed.
Knock retard uses its own short term and long
term memory program.
Long term memory stores previous detonation
information in its battery-backed RAM. The maxi-
mum authority that long term memory has over tim-
ing retard can be calibrated.
Short term memory is allowed to retard timing up
to a preset amount under all operating conditions (as
long as rpm is above the minimum rpm) except WOT.
The PCM, using short term memory, can respond
quickly to retard timing when engine knock is
detected. Short term memory is lost any time the
ignition key is turned off.
NOTE: Over or under tightening affects knock sen-
sor performance, possibly causing improper spark
control.
LOCK KEY CYLINDER
DESCRIPTION
The lock cylinder is inserted in the end of the
housing opposite the ignition switch.
OPERATION
The ignition key rotates the cylinder to 5 different
detents (Fig. 12) :
• Accessory
• Off (lock)
• Unlock
• On/Run
• Start
IGNITION INTERLOCK
OPERATION
All vehicles equipped with automatic transaxles
have an interlock system. The system prevents shift-
ing the vehicle out of Park unless the ignition lock
cylinder is in the Unlock, Run or Start position. In
addition, the operator cannot rotate the key to the
lock position unless the shifter is in the park posi-
tion. On vehicles equipped with floor shift refer to
the - Transaxle for Automatic Transmission Shifter/
Ignition Interlock.
REMOVAL AND INSTALLATION
SPARK PLUG
Always remove the ignition coil assembly by grasp-
ing at the spark plug boot, turning the assembly 1/2
turn and pulling straight back in a steady motion.
REMOVAL
(1) Prior to removing the spark plug, spray com-
pressed air around the coil area and spark plug.
(2) Remove electrical connector from ignition coil.
On 3.2/3.5L engines, it is necessary to loosen the
screws by alternating back and forth. Do not lose the
spacers under the coil when loosening the screws.
(3) Remove 2 fasteners from ignition coil.
(4) Remove ignition coil assembly.
Fig. 12 Ignition Lock Cylinder Detents
LH IGNITION SYSTEM 8D - 5
DESCRIPTION AND OPERATION (Continued)
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