Page text (OCR transcript)
EG–457
ENGINE – 2JZ–GE ENGINE TROUBLESHOOTING
DTC 78 Fuel Pump Control Circuit
CIRCUIT DESCRIPTION
The fuel pump speed is controlled at 2 steps (high speed, low speed) by the condition of the engine (starting,
light load, heavy load), when the engine starts (STA ON), the engine control module sends a Hi signal (battery
positive voltage) to the fuel pump ECU (FPC terminal).
The fuel pump ECU then outputs Hi voltage (battery positive voltage) to the fuel pump so that the fuel pump
operates at high speed.
After the engine starts, during idling or light loads, the engine control module outputs a Low signal (about 9 V)
to the fuel pump ECU, the fuel pump ECU outputs Lo battery voltage (about 9 V) to the fuel pump and causes
the fuel pump to operate at low speed.
If the intake air volume increases (high engine load), the engine control module sends a Hi signal to the fuel
pump ECU and causes the fuel pump to operate at high speed.
DTC No. | Diagnostic Trouble Code Detecting Condition | Trouble Area
78
(1) Open or short in fuel pump circuit for
1 sec. Or more with engine speed
1,000 rpm or less
(2 trip detection logic)*
2) Open in input circuit of fuel pump ECU
(FPC) with engine speed 1,000 rpm or
less
(2 trip detection logic)*
(3) Open or short in diagnostic signal line (DI)
of fuel pump ECU with engine speed
1,000 rpm or less
(2 trip detection logic)*
• Open or short in fuel pump ECU circuit
• Fuel pump ECU
• Engine control module power source circuit
• Fuel pump
• Engine control module
*: See page EG–397.
WIRING DIAGRAM
Engine Control Module
B+
GR
B-R
5 B-R 10
IB1 IC2
GR 8 24
EA1 E13 M-REL
B-R
3 EA3
B-R
4 Fuel Pump ECU
+B
5V
B-R 12
+B
FP
Data Link
Connector 1
FPC V-W 11 V-W 4 22
IC2 IJ1 E10 FPC
R/B
No.2
L-R 8 L-R 7 L-R FP
IJ1 IC2
B+
DI G 12 G 12 G 21 DI
2 IC2 IJ1 E13
E1
B-Y
R/B
No.2
EFI No.1
W-B
2A
B
Battery
SP1
Fuel Pump
L 4
E
W-B
2 SP1
W-B
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