A21043
Starter Relay
EFI Relay
Circuit Opening
Relay
Fuel Pump Relay
MREL
FPR
Tr2
Tr1
EFI No.1
IGN
ECM
FC
NE
Fuel Pump
Battery
Starter
Fuel Pump Resistor
AM2
Ignition Switch
STA
Crankshaft Position
Sensor (NE Signal)
–
DIAGNOSTICS
ENGINE
DI–179
373
DTC
P0230
Fuel Pump Primary Circuit
CIRCUIT DESCRIPTION
In the diagram below, when the engine is cranked, current flows from terminal STAR of the ECM to the starter
relay coil and also current flows to terminal STA of the ECM (STA signal).
When the STA signal and NE signal are input to the ECM, the Tr1 is turned ON, current flows to the coil of
the circuit opening relay, the relay switches on, power is supplied to the fuel pump, and the fuel pump oper-
ates.
While the NE signal is generated (engine running), the ECM keeps the Tr1 ON (circuit opening relay ON)
and the fuel pump also keeps operating.
The fuel pump speed is controlled at two levels (high speed or low speed) by the condition of the engine
(starting, light load, heavy load). When the engine starts (STA ON), the Tr2 in the ECM is OFF, so the fuel
pump relay closes and battery positive voltage is applied directly to the fuel pump. The fuel pump operates
at high speed.
After the engine starts while idling or light loads, since the Tr2 goes ON, power is supplied to the fuel pump
via the fuel pump resistor. The fuel pump operates at low speed.
DICEW–02