PleasureCraft Engine Group 5.0L, Руководство по диагностике

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4A - 6 Distributor Ignition 5.0/5.7L
MEFI 4 - PCM
Knock Sensor (KS) System Description
Purpose
To control spark knock (detonation), a knock sensor
(KS) system is used. This system is designed to retard
spark timing when excessive spark knock is detected in
the engine. The KS system allows the engine to use
maximum spark advance for optimal driveability and fuel
economy under all operating conditions.
Operation
The ECM uses a knock sensor to detect abnormal
vibration in the engine (detonation/spark knock). Mounted
on the engine block, the knock sensor produces an AC
voltage signal at all engine speeds and loads. The ECM
then adjusts the spark timing based on the amplitude and
frequency of the KS signal. The ECM uses the KS signal
to calculate an average voltage. Then, the ECM assigns
a voltage range above and below the average voltage
value. The ECM checks the KS and related wiring by
comparing the actual knock signal to the assigned voltage
range. A normal KS signal should vary outside the
assigned voltage range as shown in the NORMAL KS
fi gure. If the ECM detects a KS signal within the assigned
voltage range as shown in the ABNORMAL KS fi gure, the
applicable DTC will set.
Normal Knock Sensor Signal
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Abnormal Knock Sensor Signal
Legend
1. Upper fail region
2. Knock sensor calculated average
3. Knock sensor signal
4. Lower fail region
A diagnostic trouble code (DTC) may set for the following
conditions or faults:
ï The ECM malfunctions in a manner which will not
allow the ECM to run a diagnostic of the KS circuit.
•
The KS signal is within the assigned voltage range.
•
The KS signal is not present.
•
The Knock Sensor is improperly torqued.
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