Isuzu C22NE Workshop Manual page 403

DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 29)
Circuit Description
When the ignition switch is first turned ON, the engine
control module (ECM) energizes the fuel pump relay
which applies power to the in-tank fuel pump. The fuel
pump relay will remain ON as long as the engine is
running or cranking and the ECM is receiving 58X
crankshaft position pulses. If no 58X crankshaft
position pulses are present, the ECM de-energizes the
fuel pump relay within 2 seconds after the ignition is
turned ON or the engine is stopped.
The fuel pump delivers fuel to the fuel rail and
injectors, then to the fuel pressure regulator. The fuel
pressure regulator controls fuel pressure by allowing
excess fuel to be returned to the fuel tank. With the
engine stopped and ignition ON, the fuel pump can be
turned ON by using a command by the scan tool.
This code detects a fuel pump relay short to ground or
disconnected.
Battery Joint Cable
ECM
Fuse
15A
Fuel
Pump
Fuse
20A
Fuel
Injectors
Fuel
M
Pump
2B
FUEL PUMP RELAY SHORTED TO GROUND
DRIVEABILITY AND EMISSIONS 6E1-233
0.85W
Relay
Fuel
Pump
0.5
G/W
A13
Engine
Control
Module
(ECM)
Conditions for Setting the DTC
• ECM has commanded Fuel Pump relay to be de-
energized.
• Feedback information shows relay is still energized
or, an open contact is present.