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Hummer H1 (2006+). Manual - part 44

OBD-20

On-Board Diagnostics

_______________________________________________

Engine Cranks But Does Not Run

Step

Action

Value(s)

Yes

NOTE: Before clearing DTC(s) use the Scan Tool “Cap-
ture Info” to record Freeze Frame and Failure Record for
reference, as data will be lost when “Clear Info” function is
used.

Was the “On-Board Diagnostic System Check” per-
formed?

—

Go to step 2.

Go to OBD System

Check.

Turn ON the ignition, with the engine OFF.

Observe the DTC Information with a scan tool.

Does the scan tool display DTC P0090, P0193, P0335,

P0336, P0340, P0370, P0374, P0601, P0602,
P0603, P0604, P0611, P0612, P0642, P0643,
P0670, P0698, P0699, P1621, P1626, P1631,
P1683, P1687, or U0105?

—

Go to the Diag-

nostic trouble

code test.

Go to step 3.

Is the customer's concern with a fuel smell or fuel leak?

—

Go to Fuel

Leaks.

Go to step 4.

Observe the Actual Fuel Rail Pressure parameter with a
scan tool.
Is the pressure within the specified range?

145-261 psi

1-1.8 MPa

Go to step 5.

Go to step 15.

Observe the Ignition 1 signal parameter with a scan tool.
Is the Ignition 1 signal parameter at the specified value?

B+

Go to step 6.

Go to step 18.

Inspect for the following conditions:

• Excessive fuel in the engine oil.

• Fuel specific gravity.

Did you find and correct the condition?

—

Go to step 26.

Go to step 7.

Install the J-44638 Vacuum Gage to the fuel system
service port on the right front side of the engine.

Attempt to hand prime the fuel manager 30 times or
until the specified pressure is reached.

Can you prime the system to the specified value?

8 psi

Go to step 8.

Go to step 23.

Does the pressure measure more than the specified value
for more than 2 minutes?

2 psi

Go to step 9.

Go to step 12.

Perform the Engine Compression Test.
Repair the engine as necessary.
Did you find and correct the condition?

Go to step 27.

Go to step 10.

Did any of the cylinders emit any fuel vapor during the
Engine Compression Test?

—

Go to step 22.

Go to step 11.

Crank the engine for 15 seconds.

Observe the Actual Fuel Rail Pressure parameter
with a scan tool.

Is the Actual Fuel Rail Pressure parameter more than the
specified value?

1,450 psi

(10 MPa)

Go to step 13

Go to step 12.

05-03-06

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On-Board Diagnostics OBD-21

5745804

Prime the fuel manager to 10 psi.

Attempt to start the engine while the prime is still
above 8 psi.

—

Go to Fuel Sys-

tem Diagnosis.

Go to Fuel System

Diagnosis High

Pressure Side.

NOTE: If there is high resistance in the signal or low
reference circuits of the crankshaft position (CKP) sen-
sor the Engine Speed parameter of the scan tool will dis-
play a value more than 0. It will not be an accurate
measure of engine speed, and can cause an Engine
Cranks but does Not Run condition.
Test the CKP sensor signal and low reference circuits
for high resistance.

Did you find and correct the condition?

—

Go to step 26.

Go to step 14.

Inspect for the following conditions:

• A plugged air filter.

• A collapsed air intake duct

• The fuel heater is inoperative. If the customer

concern is that the engine will not start when am-
bient temperatures are less than 2-4˚C (35-40˚F).

• A restricted exhaust system.

Did you find and correct the condition?

—

Go to step 26.

Go to Diagnostic
Aids.

Disconnect the fuel rail pressure sensor.

Observe the Actual Fuel Rail Pressure parameter on
the scan tool.

Does the Actual Fuel Rail Pressure parameter measure
more than the specified value?

25,380 psi

(175 MPa)

Go to step 17.

Go to step 16.

Test the fuel rail pressure sensor signal circuit for a short
to ground.
Did you find and correct the condition?

—

Go to step 26.

go to step 21.

Test the fuel rail pressure sensor circuits for high resis-
tance.
Did you find and correct the condition?

—

go to step 26.

Go to step 19.

Test the ignition 1 voltage circuit of the engine con-
trol module (ECM) for a short to ground, a high
resistance or an open.

Replace the fuse, if necessary. (Refer to section 12
Figure 12-108 Fuel Injection Wiring Schematic)

Did you find and correct the condition?

—

Go to step 26.

Go to step 20.

Test for an intermittent or for a poor connection at the
fuel rail pressure sensor.
Did you find and correct the condition?

—

Go to step 26.

Go to step 24.

Clean and tighten the ECM shared ground located
on the lower right side of the engine.

Attempt to start the engine.

Does the engine start?

—

Go to step 26.

go to step 21.

Engine Cranks But Does Not Run

Step

Action

Value(s)

Yes

05-03-06

OBD-22

On-Board Diagnostics

_______________________________________________

Symptom – Intermittent Condition

Test for an intermittent and for a poor connection at the
ECM.
Did you find and correct the condition?

—

Go to step 26.

Go to step 25.

NOTE: When the fuel injector pressure lines are re-
moved, debris will fall on the fuel injector inlet fitting.
Vacuum the debris from the area to prevent the debris
from falling in the fuel injector.

Replace the fuel injectors on the affected cylinders.
Did you complete the replacement?

—

Go to step 26.

—

Before replacing the fuel filter/heater element housing,
inspect the fuel vent screw for damage or cross thread-
ing. Replace the vent screw w/O-ring if either condition
is found.
Replace the fuel filter/heater element.
Did you complete the replacement?

—

Go to step 26.

—

Replace the fuel rail pressure sensor. Refer to section 3
Did you complete the replacement?

—

Go to step 26.

—

Replace the ECM. Refer to section 12 for replacement,
setup and programming

—

Go to step 26.

—

Clear any DTCs with a scan tool.

Attempt to start the engine.

Does the engine start and continue to run?

—

Go to step 27.

Go to step 2.

Allow the engine to idle until normal operating tem-
perature is reached.

Observe the DTC Information with a scan tool.

Are any DTCs displayed?

—

Go to the Diag-

nostic Trouble

Code Test.

System OK

NOTE: Definition: The problem may or may not turn the MIL on or store a diagnostic trouble code.

Checks

Actions

Preliminary Checks

Refer to Basic Symptom Checks ( page Section: OBD–17 ).

Electrical Connections or Wiring. Poor electrical connections or wiring can cause most intermittent problems. Perform a careful

check of the suspected circuit for the following conditions.

• Poor mating of the connector halves

• Backed out terminals - Terminals not fully seated in the connector body.

• Improperly formed or damaged terminals - Carefully reform or replace all the connector

terminals in the problem circuit to ensure the proper contact tension.

• Poor terminal to wire contact - Check for poor terminal to wire connections by remov-

ing the terminal from the connector body and inspecting the terminals.

Road Test.

If a visual and physical check does not locate the cause of the problem, drive the vehicle with a
DVOM connected to the suspected circuit, or use a scan tool. An abnormal voltage or scan
reading, when the problem occurs, indicates the problem.

Engine Cranks But Does Not Run

Step

Action

Value(s)

Yes

05-03-06

______________________________________________

On-Board Diagnostics OBD-23

5745804

Symptom – Hard Start

Intermittent Malfunction
Indicator Lamp (MIL).

The following can cause an intermittent MIL and no DTCs:

• Electrical system interference caused by a malfunctioning relay, engine control module

(ECM) driven solenoid, or switch - All of these can cause a sharp electrical surge. Nor-
mally, the problem will occur when the malfunctioning component is operating.

• The improper installation of electrical devices, such as lights, 2-way radios, cell phones, etc.

• The malfunction indicator lamp (MIL) circuit intermittently shorted to ground.

• Poor ECM grounds.

Loss of DTC Memory.

Check for loss of DTC memory by disconnecting the engine coolant temperature (ECT) sensor
and idling the engine until the MIL turns “ON”. An engine coolant temperature (ECT) DTC
should store and remain in memory when turning “OFF” the ignition for at least 10 seconds. If
not, the ECM is malfunctioning.

Additional checks

Check for an open diode across the A/C compressor clutch and for other open diodes.

NOTE: Definition: the engine cranks OK, but does not start for a long time. The engine does eventually run, or may start but im-
mediately die.

Checks

Action

Preliminary checks.

• Refer to Basic Symptom Checks ( page Section: OBD–17 ).

• Make sure that the driver is using the correct starting procedure.

Sensor checks.

Check the engine coolant temperature sensor. Use the scan tool in order to compare the engine
coolant temperature with the Ambient Air Temperature on a cold engine. If the coolant temper-
ature reading is more than 5˚ more or less than the Ambient Air Temperature on a cold engine,
check for a high resistance in the coolant sensor circuit or the sensor itself.

Fuel system checks.

• Check the supply to the injection pump.

• Check for air in the fuel system.

• Check the fuel return from the injection pump.

• Check the engine shut-off solenoid operation.

• Check the fuel injection nozzles.

• Check the fuel tank cap vent.

• Check for an internal injection pump problem.

Electrical system check.

• Check the glow plug operation.

• Check for a slow cranking speed.

Air intake system checks.

• Check the air cleaner and the air intake ducts for a restriction.

• Check For a restriction in the turbo charger inlet duct.

• Check for a restriction in the intake manifold.

Exhaust system check.

Check the exhaust system for a possible restriction.

NOTE: Definition: The problem may or may not turn the MIL on or store a diagnostic trouble code.

Checks

Actions

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