1990 MAZDA 232 octane

F2 CONTROL SYSTEM
KNOCK CONTROL SYSTEM [BP TURBO]
This svstem retards the ignition timina when enaine knocking occurs because of usage of low octane fuel, etc.
1NTAKE
MANIFO
KNOCK SENSOR
(INSTALLED BETWEEN No.2 AND
No.3 CYLINDER)
IGNITER
KNOCK iX?NTROL
UNIT
Operation
When the engine vibrates, the knock sensor generates a slight voltage signal that is the sent to the knock
control unit. The knock control unit determines whether the signal is a knocking signal. If it is a knocking
signal, the ignition spark is retarded according to the intensity of the knock to a maximum of 4O.
Inhibition of spark retardation
In order to improve drivability and fuel economy, the ECU inhibits the above spark retardation when the
‘engine load Ls light, the coolant temperature is below O°C (32OF), the engine is cranking during engine test
conditions.
Note
l The knock ~ensur and knock control unit cannot be inspected individually.
When a matfunction code number 05 is indicated, replace the knock controt unit or sensor
only after inspecting the related wiring and connectors.
F2-22

I
F2
fNSPECTlON ACTION
I Check if cootrng system IS OK’
YES Go to next step
No Repair or reptace
l Thermostat l
l Electric cooling fan * l Radiator*
5 Try known good ECU and check if condltlon Yes Replace ECU * rnproves
NO Change fuel to another brand or use
higher octane fuel
l Refer to 323 Workshop Manual [1203-l O-89F (Europe) or It 204-I O-89F (Australia)]. %%‘3OF2-748 -
F2-4 I