Diagnostic Trouble Code (DTC) P0327 Knock Sensor Circuit Fault

Diagnostic Trouble Code (DTC) P0327

Knock Sensor Circuit Fault



Circuit Features



  • Detecting engine detonation is the primary task of the knock sensor system(KS).
  • This system is specially empowered to enable the transaxle control module(TCM)/engine control module(ECM) to thwart  ignition control spark timing on the basis of the signals received from the KS.
  • The system is so devised that the KS can generate an AC signal which under a  ‘no knock ‘condition on the KS circuit can read nearly 0.007V AC.
  • The number of knocks being received determines the amplitude and frequency of the KS.
  • A signal-to-noise enhancement filter (SNEF) module (a non replaceable knock filter module) is a part of the ECM in this circuit.
  • The SNEF ensures if any knock is being created on the basis of the comparison of the signals on the KS circuit including the voltage level on the noise channel.
  • The noise channel guides the ECM to disregard any inaccurate knock signal by collecting information of the amount of normal engine mechanical noise being created.
  • Engine speed and load are the key factors on which the normal engine noise depends.
  • A DTC will be prompted as soon as the ECM understands that an unusually low noise channel voltage level is being regulated.






                                               When does DTC set?


In this circuit DTC sets when

a)       There is a failure in the knock sensor SPI bus during the initial 10 seconds.

Or  when



1)       The knock sensor voltage is < 0.3V.

2)       The engine coolant temperature is > 60°C(145°F).

3)       The engine speed is > 1,500rpm.

4)       The mass air flow is > 180mg/tdc.

Or when

  • The variation between the original signal valve and filtering valve is < 5%.
  • The engine coolant temperature is > 60°C(145°F).
  • The mass air flow is > 170mg/tdc.




Task boosted after DTC sets

When will DTC clear?

1) The Malfunction Indicator Lamp (MIL) will be seen glowing after three repetitive trips with a fail.


1) The MIL will go off after four repetitive ignition cycles where the diagnostic runs flawlessly.


2) The ECM will begin to record operating conditions at the time when the diagnostic fails which will be stored in the Freeze Frame.


2) A history DTC will clear by itself after 40 successive warm-up cycles flawlessly

3) A history Diagnostic Trouble Code (DTC) will be stored.



3) The scan tool can be used to remove all existing DTCs.



4) Disconnecting the ECM battery feed for 10 seconds





Diagnostic Assistance



It is advised that you examine and repair any unusual engine noise before referring to the diagnostic table.

Any circuitry that is suspected to be the source of the engine noise  should be checked for the following conditions :

a)       Backed-out terminals

b)       Improper mating

c)       Broken locks

d)       Improperly formed

e)       Damaged terminals

f)         Poor terminal-to-wire connection

g)       Physical damage to the wiring harness