Page text (OCR transcript)
EG–568
ENGINE – 2JZ–GTE 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 Low 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–503.
WIRING DIAGRAM
Engine Control Module
B+
GR
B-R 5
EA3
L-O L-O 10 L-O 8 GR 24
B-R IC2 EA1 E10 M-REL
G-R 4
AR
12
B 1 Fuel Pump ECU
FP Data Link
Connector 1 +B
L-R FPC 11 4 V-W 22 FPC
J1K 7 L-R FP IC3K J1 E10
J1K 2
+B+
B-R 7 DI 12 G 12 G 21 DI
EFI No.2 Relay 6 BP IC3K J1 E10
E
EFI Main Relay L 4 8
W-B
R/B Fuel Pump
No.2 W-B
2 W-B
EFI No.2 5
EFI No.1 W-B W-B
R/B
No.2
FI6833