1F–146 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F170
DIAGNOSTIC TROUBLE CODE (DTC) – P0327 KNOCK SENSOR CIRCUIT FAULT
Circuit Description
The knock sensor(KS) system is used to detect engine
detonation, allowing the engine control module(ECM) to
retard ignition control spark timing based on the KS sig-
nal being received. The KS produces an AC signal so
that under a no knock condition the signal on the KS cir-
cuit measures about 0.007V AC. The KS signal’s ampli-
tude and frequency depend upon the amount of knock
being experienced. The ECM contains a non-replace-
able knock filter module called a signal-to-noise en-
hancement filter (SNEF) module. This filter module in
the ECM determines whether knock is occurring by
comparing the signal level on the KS circuit with the volt-
age level on the noise channel. The noise channel al-
lows the ECM to reject any false knock signal by
knowing the amount of normal engine mechanical noise
present. Normal engine noise varies depending on en-
gine speed and load. When the ECM determines that an
abnormally low noise channel voltage level is being ex-
perienced, a DTC P0327 will set.
Conditions for Setting the DTC
D Knock sensor SPI bus in failure during 7 seconds.
D The knock sensor voltage is below 0.2V.
D Engine Coolant Temperature is higher than 80°C
(176°F).
D Engine rpm is more than 2,500rpm.
D Mass air flow is higer than 180mg/tdc.
Action Taken When The DTCs Sets
D The Malfunction Indicator Lamp (MIL) will illuminate.
D The ECM will record operating conditions at the time
the diagnostic fails. This information will be stored in
the Freeze Frame and Failure Records buffers.
D A history DTC is stored.
Conditions for Clearing the MIL/DTC
D The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
D A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
D DTC(s) can be cleared by using the scan tool.
DIAGNOSTIC AIDS
Check and correct any abnormal engine noise before
using the diagnostic table.
Any circuitry that is suspected as causing engine noise
complaint should be thoroughly checked for the follow-
ing conditions :
D Backed-out terminals.
D Improper mating.
D Broken locks.
D Improperly formed.
D Damaged terminals.
D Poor terminal-to-wire connections.
D Physical damage to the wiring harness.
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