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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

0.85W

Battery Joint Cable

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.

Reinstall the fuel pump relay.

DTC (Flash DTC = 29)

Fuel Pump Relay Shorted To Ground

Step

Action

Value(s)

Yes

Was the “On-Board Diagnostic (OBD) System

Check” performed?

Go to Step 2

Go to OBD

System

Check

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

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

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

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

Check for short to ground between the ECM and the fuel

pump relay.

Was a problem found?

Verify repair

Go to Step 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

Replace the EPROM or ECM.

Is the action complete?

Note) Refer to 6E1-243.

Verify repair

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

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

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

Repair the open circuit in the fuel pump ground wire.

Is the action complete?

Verify repair

1. Re-connect the horn relay in its proper location.

2. Replace the fuel pump relay.

Is the action complete?

Verify repair

Replace the fuel pump.

Is the action complete?

Verify repair

Content .. 99 100 101 102 ..