Isuzu engine C22NE / 22LE / 20LE. Manual — part 101
DRIVEABILITY AND EMISSIONS 6E1-233
Fuel
Pump
Fuse
20A
Relay
Fuel
Pump
A13
Fuel
Injectors
Fuel
Pump
M
0.85W
Battery Joint Cable
2B
0.5
G/W
Engine
Control
Module
(ECM)
ECM
Fuse
15A
DIAGNOSTIC TROUBLE CODE (DTC) (Flash DTC = 29)
FUEL PUMP RELAY SHORTED TO GROUND
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.
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.
6E1-234 DRIVEABILITY AND EMISSIONS
Action Taken When the DTC sets
• The ECM will turn ON the Malfunction Indicator
Lamp.
Conditions for Clearing the DTC
Once the ECM determines that a fault(s) has been
rectified then the CEL will switch OFF, although the
fault code will remain in the ECM memory.
Any fault codes will remain in ECM memory until -
1. They are cleared by disconnecting the Battery for
more than 30 seconds.
2. A service tool such as Tech 2 is used to clear them.
3. Ten consecutive starts without logging a fault.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:
• Poor connection or damaged harness - Inspect the
ECM harness and connectors for improper mating,
broken locks, improperly formed or damaged
terminals, poor terminal-to-wire connection, and
damaged harness.
• This malfunction detects a fuel pump relay short to
ground or disconnection.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. If the fuel pump is operating but incorrect pressure
is noted, the fuel pump wiring is OK and the “Fuel
System Pressure Test” chart should be used for
diagnosis.
Caution: To reduce the risk of fire and
personal injury:
• It is necessary to relieve fuel system
pressure before connecting a fuel pressure
gauge. Refer to Fuel Pressure Relief
Procedure, below.
• A small amount of fuel may be released
when disconnecting the fuel lines. Cover
fuel line fittings with a shop towel before
disconnecting, to catch any fuel that may
leak out. Place the towel in an approved
container when the disconnect is
completed.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood
relay center.
3. Start the engine and alow it to stall.
4. Crank the engine for an additional 3 seconds.
Fuel Pressure Gauge Installation
1. Remove the shoulder fitting cap.
2. Install fuel pressure gauge 5-8840-0378-0 to the
fuel feed line located in front of and above the right
side valve cover.
3.
Reinstall the fuel pump relay.
DTC (Flash DTC = 29)
Fuel Pump Relay Shorted To Ground
Step
Action
Value(s)
Yes
No
1
Was the “On-Board Diagnostic (OBD) System
Check” performed?
-
Go to Step 2
Go to OBD
System
Check
2
1. Read the “Caution” above.
2. Relieve the fuel system pressure and install the fuel
pump pressure gauge to the test fitting.
3. Use a scan tool to command the fuel pump ON.
Is there an immediate pressure build-up which indicates
the pump is running?
-
Go to Step 3
Go to Step 4
DRIVEABILITY AND EMISSIONS 6E1-235
DTC (Flash DTC = 29)
Fuel Pump Relay Shorted To Ground (Cont’d)
Step
Action
Value(s)
Yes
No
3
1. Verify that the pump is not running by removing the fuel
filler cap and listening.
2. Check the fuel pump relay connector is loosely fitting or
disconnected.
Repair it necessary.
3. Command the pump ON with the scan tool.
Did the pump turn OFF after 2 seconds?
-
Test
completed
Go to Step 4
4
1. Ignition OFF.
2. Remove the fuel pump relay.
3. Connect a test light between the two wires that connect
to the fuel pump relay pull-in coil.
4. Ignition ON.
Did the test light illuminate for 2 seconds and then turn
off?
-
Go to Step 9
Go to Step 5
5
1. With a test light connected to battery (
−), probe the fuel
pump relay connector at the wire which runs form the
relay pull-in coil to the ECM.
2. Ignition ON.
Did the test light illuminate for 2 seconds and then turn
off?
-
Go to Step 6
Go to Step 7
6
Check for short to ground between the ECM and the fuel
pump relay.
Was a problem found?
-
Verify repair
Go to Step 7
7
1. Check the fuel pump relay circuit for a poor terminal
connection at the ECM.
2. If a problem is found, replace terminal as necessary.
Was a problem found?
-
Verify repair
Go to Step 8
8
Replace the EPROM or ECM.
Is the action complete?
Note) Refer to 6E1-243.
-
Verify repair
-
9
1. Honk the horn to verify that the horn relay is
functioning.
2. Substitute the horn relay for the fuel pump relay.
3. Leave the test light connected as in step 12.
4. Command the fuel pump ON with the scan tool.
Did the test light illuminate for 2 seconds when the fuel
pump was commanded ON?
-
Go to Step 13
Go to Step 10
10
1. Re-connect the horn relay in its proper location.
2. Check for a short circuit, blown fuse or open circuit
between the relay and the fuel tank.
Is the action complete?
-
Verify repair
-
11
1. With the fuel pump electrical connector at the fuel tank
disconnected, connect a test light between the feed
wire and the ground wire (harness side).
2. Command the fuel pump ON with a scan tool.
Did the test light illuminate for 2 seconds?
-
Go to Step 14
Go to Step 12
6E1-236 DRIVEABILITY AND EMISSIONS
DTC (Flash DTC = 29)
Fuel Pump Relay Shorted To Ground (Cont’d)
Step
Action
Value(s)
Yes
No
12
Repair the open circuit in the fuel pump ground wire.
Is the action complete?
-
Verify repair
-
13
1. Re-connect the horn relay in its proper location.
2. Replace the fuel pump relay.
Is the action complete?
-
Verify repair
-
14
Replace the fuel pump.
Is the action complete?
-
Verify repair
-
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