1990 MAZDA 232 ECU

FUEL SYSTEM F2
Two-stage WeI pump operation
Engine running (Except heavy load or cranking)
The ECU 1 I circuit is ON, opening the contact plate in the fuel pump resistor/relay. Current from the circuit
opening relay to the fuel pump flows through the resistor in the fuel pump resistor/relay, and the voltage
to the fuel pump is reduced to approx. WV, causing the fuel pump to operate at a reduced speed to im-
move fuel pump longevity.
MAIN RELAY
Engine under heavy load or cranking
The ECU 1 I circuit is OFF and the contact plate in the fuel pump resistor/relay is closed. Unreduced battery
current flows to the fuel pump through the contact plate, causing the fuel pump speed and output to be
increased to meet the demands of the engine.
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93GW2-725
FZ-17

F2 FUEL SYSTEM
93GOF2-726
FUEL PUMP RESISTOR/RELAY [BP TURBO]
The fuel pump resistorlretay supplies battery voltage to the
fuel pump when the ECU 11 circuit is OFF, and approx. 1 OV
when the ECU 11 circuit is ON. It is mounted on the firewall.
TRANSFER PUMP CONTROL
Outline
The fuel tank is buitt with separate right and left sections to accommodate the. installation of the propeller
shaft. As fuel is puited from the right side of the tank, the transfer pump pumps the fuel from the left to the
right (fuel pumb) side to balance the fuel level.
FUEL IN LEFT TANK
I
FUEL PUMP CONTROL. UNIT
/ TRANSFER PUMP
TRANSFER PUMP SWITCH: OFF
NO FUEL IN LEFT
TANK
FUEL PUMP CONTROL UNIT / TRiNSFER PUMP
TRANSFER PUMP SWITCH: UN
93GOF2-727
Operation 1. Whenever the ignition switch is ON and fuel is in the left (transfer pump)
side of the fuel tank the fuel pump switch is open, the transfer pump circuit in the fuel pump control unit is
closed, and the transfer pump
operates.
2. When the fuel in the left side of the tank drips betow a specified point, the fuel pump switch is grounded
and the transfer pump stops operation.
3. To prevent the transfer pump from
being turned ON and OFF repeatedly, possibly shorting the life of the
pump, when the vehicle is driven on a rough
road and the fuel level is low, there is a ten-second delay
circuit in the control unit to delay the turning ON and OFF the pump.
f2--I 8

CONTROL SYSTEM
WE~DOST WARNlNG BUZZER [BP TURBO]
To improve engine reliability, the overboost warning buzzer installed in the instrument cluster sounds during
overboost conditions as detected by engine
speed and intake air amount caiculations within the ECU. The
driver is thus warned to reduce engine
speed.
DETECTtON
OVERBOOST
BUZZER
TURBOCHARGE INDICATOR [BP TURBO]
When the turbocharger boost pressure calcul’ated by intake air amount and engine speed reaches the predeter-
mined level and the transaxle is in gear, the turbocharge indicator illuminates to inform the driver of turbocharge
operation.
1
AIRFLOW METER
DISTRI BUTUR
rd” i
4 NEUTRAUCLUTCH
SWITCH ECU
* CALCULATION
-, OF
BOOST
PRESSURE
TURBOCHARGE
INDICATOR

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

F2 CONTROLSYSTEM
AK CUT-OFF SYSTEM (AI-X)
To improve the retiability of the engine at high temperature condition, the water thermoswitch on the radiator
is switched OFF above approx. II I “C (232OF) and stops the A/C operation.
ECU
NC OPERATION BLOWER FAN
WATER
THERMOSWITCH
IABOVE
111 OC (232OF): OFF]
NC SWITCH
IGNITION
T
l 1
BLOWER SWITCH
MAGNET
CLUTCH
93GOF2-73
F2-24

SUPPLEMENTAL SERVICE INFORMATION F2
SUPPLEMENTAL SERVICE INFORMATION
The following points in this section are changed in comparison to the Mazda 323 Workshop Manual
[I 203-I U-89F (Europe) or 120410-89F {Australia)].
intake air system components [BP Turbo]
l Removalllnspectionll nstaltation
WASTEGATE [BP Turbo]
l Inspection
WASTEGATE SULENOlD VALVE [BP Turbo]
l Inspection
Turbocharger [BP Turbo]
l Inspection
l Removalllnstaltation
Air bypass valve [BP Turbo]
l Removal/hstallation
l 1 nspection
lntetcoolet [BP Turbo]
l RemovaMnspection/tnstaltation
Fuel tank
l Removal ! Inspection I Installation
Fuel pump control unit [BP Tubto]/4x4 control unit [BP SOHC]
l 1 nspection
l Replacement
Transfer pump switch
l Inspection
l Replacement
Transfer pump
l Inspection
l Replacement
Fuel pump resistor/relay
l System operation
l Inspection
injector [8P Turbo]
l Volume test
Exhaust system components
l Removal / 1 nspection / Installation
Engine control unit (ECU) [BP Turbo]
l Terminal voftage
Oxygen sensor [BP Turbo]
l Inspection
l Replacement
Knock sensor [BP Turbo]
l Replacement 93GOFZ736
F2-25

SELF-DIAGNOSIS FUNCTtON F2
Q3en
or short ci rculi - ON
26
OFF -
ON
34
OFF
ON
42
OFF
Caution
l If there is more than one failure present, the code numbers will be indicated in numerical or-
der, lowest number first.
l After repairing a failure, turn off the ignition switch, disconnect the negative battery cable,
and depress the brake pedai for at least five (5) seconds to erase the malfunction code(s) from
the ECU memory.
f2--27

F2 SELF-DIAGNOSlS FUNCTION
Troubleshooting
If a malfunction code number is shown on the SST (49 l-l01 8 9Ai, 49 B019 9AO), check for the cause
using the chart related to the code number shown, [Regarding code numbers except 05, 24, and 42, refer
to “Troubleshooting” in Workshop Manual [I 203-I O-89F (Europe) or 1204-f 0-89F (Australia)].
r C :ODE No. 05 (KNOCK CONTROL UNIT)-BP TUR80
;TEP
2
3 I INSPECTION
Check knock sensor and knock control unit
circuit for poor connectlon ACTtON
Yes Repalr or replace connector
Check knock control unit terminal voltage with
ignition switch ON
Check that voltage at ECU terminal 2J is
approx. 4V at idle
rs7 page F2-64 Yes Recheck ECU connector for poor
connection
4 If OK, replace ECU
4 If not OK, repair or replace connector
NO Repair wiring harness (R/Y) between
ECU terminal 2J and knock control unit
93GOF2-7:
Circuit Diagram
I
ECU
IGNITION
SWITCH
15A BATTERY
MAIN
RELAY
(FUEL 1N.J)
l W/L Y/i3 G/O W RIB R/L
YIL
jr- -- - - 1 BlLG
-
-
MCK CONTROL
I
. :
MAIN RELAY (FUEL INJ)
W/G BIW
C&=&A
KNOCK CONTROL UNIT
W/R EMLG RN Y/L
1
KNOCK SENSOR