Hummer H2. Manual - part 1502

ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS (WITHOUT SPECIAL TOOL AND E85)

Description

Water contamination in the fuel system may cause driveability conditions such as hesitation, stalling, no start,
or misfires in one or more cylinders. Water may collect near a single fuel injector at the lowest point in the fuel
injection system, and cause a misfire in that cylinder. If the fuel system is contaminated with water, inspect the
fuel system components for rust, or deterioration.

Alcohol concentrations of 10 percent or greater in fuel can be detrimental to fuel system components. Alcohol
contamination may cause fuel system corrosion, deterioration of rubber components, and subsequent fuel filter
restriction. Some types of alcohol are more detrimental to fuel system components than others. Ethanol is
commonly used in gasoline, but in concentrations of no more than 10 percent. Some fuels, such as E85, contain
a very high percentage of ethanol. Fuel with more than 10 percent ethanol may cause driveability conditions
such as hesitation, lack or power, stalling, or no start.

Alcohol in Fuel Testing Procedure

2. Inspect for leaks in any of the following locations:

The fuel tank, fill limiter vent valve, pressure relief valve, and
the grade vent valves-Refer to Fuel Tank Replacement .

The fuel sender housing and the fuel sender seal - Refer to
Fuel Sender Assembly Replacement .

The fuel tank pressure (FTP) sensor seal - Refer to Fuel Tank
Pressure Sensor Replacement .

The EVAP vapor pipes - Refer to Evaporative Emission
(EVAP) System Hoses/Pipes Replacement (Engine
Compartment EVAP Pipe) or Evaporative Emission
(EVAP) System Hoses/Pipes Replacement (Chassis EVAP
Pipe) or Evaporative Emission (EVAP) System
Hoses/Pipes Replacement (EVAP Vent Pipe) or
Evaporative Emission (EVAP) System Hoses/Pipes
Replacement (Rear EVAP Fuel Tank Pipe) and
Evaporative Emission (EVAP) Canister Replacement .

The fuel fill pipe and hose - Refer to Filler Tube
Replacement .

Did you find and correct the condition?

Go to

Step 8

Go to

Diagnostic

Aids

Replace the fuel tank. Refer to Fuel Tank Replacement .
Did you complete the repair?

Go to

Step 8

Replace the leaking fuel pipe. Refer to Fuel Hose/Pipes Assembly
Replacement .
Did you complete the replacement?

Go to

Step 8

Operate the system in order to verify the repair.
Did you correct the condition?

System

Go to Step 2

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be
detected. The sample should be bright and clear. If alcohol contamination is suspected then use the following
procedure to test the fuel quality.

1. Using a 100 ml specified cylinder with 1 ml graduation marks, fill the cylinder with fuel to the 90 ml

mark.

2. Add 10 ml of water in order to bring the total fluid volume to 100 ml and install a stopper.

3. Shake the cylinder vigorously for 10-15 seconds.

4. Carefully loosen the stopper in order to release the pressure.

5. Re-install the stopper and shake the cylinder vigorously again for 10-15 seconds.

6. Put the cylinder on a level surface for approximately 5 minutes in order to allow adequate liquid

separation.

If alcohol is present in the fuel, the volume of the lower layer, which would now contain both alcohol and
water, will be more than 10 ml. For example, if the volume of the lower layer is increased to 15 ml, this
indicates at least 5 percent alcohol in the fuel. The actual amount of alcohol may be somewhat more because
this procedure does not extract all of the alcohol from the fuel.

Particulate Contaminants in Fuel Testing Procedure

The fuel sample should be drawn from the bottom of the tank so that any water present in the tank will be
detected. The sample should be bright and clear. If the sample appears cloudy, or contaminated with water, as
indicated by a water layer at the bottom of the sample, use the following procedure to diagnose the fuel.

1. Using an approved fuel container, draw approximately 0.5 liter of fuel.

2. Place the cylinder on a level surface for approximately 5 minutes in order to allow settling of the

particulate contamination.

Particulate contamination will show up in various shapes and colors. Sand will typically be identified by a white
or light brown crystals. Rubber will appear as black and irregular particles. If particles are found clean the entire
fuel system thoroughly. Refer to Fuel System Cleaning .

ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS (WITH SPECIAL TOOL)

Description

Ethanol concentrations of greater than 10 percent in non-blended gasoline, or greater than 85 percent with E85
blended gasoline for flexible fuel applications, can cause driveability conditions and may contribute to fuel
system deterioration. Excessive ethanol concentrations can result in driveability conditions such as hesitation,
lack of power, stalling, or a no start, and may contribute to fuel system corrosion, deterioration of fuel system
components, and a restricted fuel filter.

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

Test Procedure

1. Test the fuel composition using J 44175 Fuel Composition Tester and J 44175-3 Instruction Manual.

2. If water appears in the fuel sample, perform the following steps:

1. Clean the fuel system. Refer to Fuel System Cleaning .

2. Replace the fuel filter if the vehicle is equipped with a serviceable fuel filter.

3. Subtract 50 from the reading on the DMM in order to obtain the percentage of alcohol in the fuel sample.

Refer to the examples in the Fuel Composition Test Examples table.

4. If the non-blended gasoline fuel sample contains more than 15 percent ethanol, or if the E85 blended

gasoline fuel sample contains more than 85 percent ethanol, add fresh, regular gasoline to the vehicle's
fuel tank.

5. Test the fuel composition.

6. If additional testing indicates that the ethanol percentage is still more above 15 percent for a non-blended

gasoline sample, drain and replace the vehicle's fuel. Refer to Fuel System Cleaning . If additional
testing indicates that the E85 blended gasoline sample is still above 85 percent, continue adding fresh,
regular gasoline until the ethanol content is 85 percent or less.

Fuel Composition Test Examples

ELECTRONIC IGNITION (EI) SYSTEM DIAGNOSIS

Circuit Description

The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module
(PCM) controls the ignition operation through eight individual ignition control (IC) circuits. Each bank of four
ignition coils is connected to the PCM, power, or ground by the following circuits:

Low reference

Chassis ground

Ignition 1 voltage

The appropriate IC circuit

The PCM triggers an ignition coil by grounding the appropriate IC circuit using information from the crankshaft
position (CKP) and camshaft position (CMP) sensors.

Diagnostic Aids

Frequency (Hz)

Subtract 50

Ethanol Percent

Example A

50 Hz

-50

Example B

65 Hz

-50

Example C

129 Hz

-50

Example D

135 Hz

-50

IMPORTANT: A missing CMP sensor signal may cause a long crank condition.

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

For an intermittent condition, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

5: Monitoring the misfire current counters determines if a fault is present.

12: A good indication that the fuse is open is all off the misfire current counters are incrementing on one
side of the engine. Inspect the ignition positive voltage circuit for a grounded circuit. If the fuse is open
and the ignition coil circuits are OK, inspect the injector circuits for being grounded.

Electronic Ignition (EI) System Diagnosis

The CKP signal must be available for the engine to start. The CMP signal is not
needed to start and operate the engine. The PCM can determine when a
cylinder is on either the firing or exhaust stroke by the 24X signal.
Remove any debris from the PCM connector surfaces before servicing the
PCM. Inspect the PCM connector gaskets when diagnosing or replacing the
PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water
intrusion into the PCM.

Step

Action

Value

(s)

Yes

Schematic Reference:Engine Controls Schematics
Connector End View Reference:Engine Controls Connector End Views or Powertrain Control
Module (PCM) Connector End Views

Did you perform the Diagnostic System Check -
Engine Controls?

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

Attempt to start the engine.
Does the engine start and run?

Go to Step 5

Go to Step 3

1. Observe the Engine Speed parameter with a

scan tool.

2. Crank the engine.

Does the scan tool indicate RPM is present?

Go to Step 7

Go to Step 4

Is DTC P0335, P0336, or P0351-P0358 also set?

Go to Diagnostic

Trouble Code

(DTC) List

Go to Step 16

1. Idle the engine.

2. Observe the misfire current counters on the

scan tool.

Does the scan tool display any misfire current
counters incrementing?

Go to Step 6

Go to Diagnostic

Aids

2004 Hummer H2

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

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