Hummer H1 (2006+). Manual - part 45

OBD-24

On-Board Diagnostics

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Symptom – Surges/Chugs

Symptom – Lack of Power, Sluggishness, or Sponginess

Engine mechanical checks.

Check the engine for the following conditions:

• Improper valve timing.

• Low compression.

• Worn rocker arms.

• Broken or weak valve springs.

• Worn camshaft lobes.

Additional checks.

• Check for a no crank signal.

• Check the service bulletins for a control module software update.

NOTE: Definition: The engine has a power variation under a steady throttle or cruise. the vehicle seems to speed up and slow
down without a change in pressure on the accelerator.

Checks

Action

Preliminary checks.

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

• Be sure the driver understands the torque converter clutch operation.

• Be sure the driver understands the A/C compressor operation.

• Use the scan tool in order to ensure the reading of VSS matches the vehicle speedometer.

Fuel system checks.

C

heck the fuel pressure while the condition exists.

Additional checks.

• Check the control module grounds for being clean, tight, and in their proper locations.

• Check the generator output voltage. Repair if less than 9 or more than 16 volts.

• Check the vacuum lines for kinks or links.

• Check the TCC operation.

NOTE: Definition: The engine delivers less than the expected power. There is less on no increase in speed when partially applying
the accelerator pedal.

Checks

Actions

Preliminary checks.

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

• Compare the vehicle with a similar unit. make sure that the vehicle has an actual problem.

• Remove the air filter.

• Check for dirt, or for air ducts being plugged. Clean and replace if necessary.

• Inspect the transmission shift pattern and the down shift operation. 

• Check the fuel quality.

• Check the engine oil level and quality.

Fuel systems checks.

• Check the fuel supply to the injection pump and the fuel return from the injection pump.

• Check the fuel pump operation.

• Check for malfunction fuel injection nozzles.

Exhaust system checks.

• Check the exhaust system for a possible restriction.

• Inspect the exhaust system for damaged or collapsed pipes.

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

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 On-Board Diagnostics  OBD-25

5745804

Symptom - Fuel Knock/Combustion Noise

Air intake system checks.

• Check for an air leakage or a restriction in the air inlet ducts or the intake manifold.

• Check for a worn or a damaged turbo charger turbine wheel, shaft, or compressor wheel.

Engine mechanical check

Check the engine for the following:

• Low compression.

• Improper valve timing.

• Improper or worn camshaft.

Additional checks.

• Check the control module grounds for being clean, tight, and in their proper location.

• Check the torque converter clutch operation.

• Check the A/C operation.

• Check the generator output voltage. Repair if voltage is less than 9v and more than 16v.

NOTE: Definition: A mild to severe ping which is usually worse upon acceleration. The engine makes sharp metallic knocks
which change with the throttle opening.

Checks

Action

Preliminary checks.

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

• Make sure that the vehicle has an actual problem.

• Check the fuel quality.

Cooling system checks.

• Check fro obvious overheating problems.

• Check for a low engine coolant level.

• Check for a loose water pump belt.

• Check for restricted air flow through the radiator, or restricted coolant flow.

• Check for a malfunctioning or incorrect thermostat.

• Check for a correct coolant solution. The solution should be a 50/50 mix of anti-freeze 

and water.

Sensor check.

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 for air leaks in the fuel supply to the injection pump.

• Check the injection pump static timing.

• Check the injection nozzles.

Engine mechanical checks.

• Check for incorrect basic engine parts such as the cam, the heads, the pistons, etc.

• Check for an excessive oil entering the combustion chamber.

Additional checks.

Check the service bulletins for control module software updates.

NOTE: Definition: The engine delivers less than the expected power. There is less on no increase in speed when partially applying
the accelerator pedal.

Checks

Actions

OBD-26

On-Board Diagnostics

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Symptom - Hesitation, Sag, Stumble

D

Symptom - Cuts Out, Misses

NOTE: Definition: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur
at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. The condition may
cause the engine to stall, if severe enough.

Checks

Action

Preliminary check.

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

Fuel system checks.

• Check the fuel pressure.

• Check for water contamination in the fuel.

• Perform the injector balance test.

• Check for a low fuel pressure after a cold start or during a moderate or a full throttle ac-

celeration. If the fuel pressure drops below specification, there is possibly a malfunc-
tioning fuel pump or a restriction in the fuel system.

Additional checks.

• Check the service bulletins for any control module software updates.

• Check the generator output voltage.

NOTE: Definition: A steady jerking that follows the engine speed, usually more pronounced as the engine load increased. The vi-
bration is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound during idle, low speed,
or hard acceleration due to the fuel starvation that can cause the engine to cut-out.

Checks

Action

Preliminary check.

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

Ignition system checks.

Check for a cylinder misfire:

• Start the engine.

• Allow the engine to stabilize.

• Perform the injector balance test.

• If there is no RPM drop on one or more of the cylinders, or if there is an excessive vari-

ation in drop, refer to Engine mechanical checks.

Engine mechanical checks

• Perform a cylinder compression check. 

• Check the engine for the following conditions:

• Improper valve timing.

• Bent pushrods.

• Worn rocker arms.

• Worn camshaft lobes.

• Broken or weak valve springs.

• Check the intake and exhaust manifold passages for a casting flash.

Fuel system checks.

• Check the fuel system for a plugged fuel filter, low fuel pressure,. etc.

• Check for water contamination in the fuel.

Additional checks.

• Check for electromagnetic interference- The EMI on the reference circuit can cause a 

missing condition.

• Monitoring the engine RPM with the Tech 2 can detect an EMI.

• A sudden increase in the RPM with little change in the actual engine RPM will indicate 

that an EMI is present.

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 On-Board Diagnostics  OBD-27

5745804

Symptom - Poor Fuel Economy

Symptom - Excessive Smoke

NOTE: Definition: The fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, the economy is
noticeably lower than previously shown by an actual road test on this vehicle.

Checks

Action

Preliminary Checks

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

• Check the air cleaner filter for dirt or being plugged.

• Visually or physically inspect the vacuum hoses for splits, kinks, and proper connections.

• Perform the Diagnostic System Check.

• Check the driving habits of the owner. 

• Is the A/C “ON” full time? Is the defroster mode “ON”?

• Are the tires at the correct pressure?

• Are any excessively heavy loads being carried?

• Is the acceleration too much, too often?

• Suggest to the owner to fill the tank and recheck the fuel economy

Fuel system checks.

• Check the fuel type and quality.

• Check the fuel pressure.

Cooling system checks.

• Check the engine coolant level.

• Check the engine thermostat for the wrong heat range or possible being stuck open.

Additional checks.

• Check the transmission shift pattern.

• Check the torque converter clutch operation. When the TCC is commanded “ON”, the 

Tech 2 should indicate an RPM drop.

• Check the service bulletins for any control module software updates.

• Check for dragging brakes.

NOTE: Definition: White, black, gray or blue smoke under load, idle or start up hot or cold.

Checks Action

Preliminary check

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

• Make sure the vehicle has an actual problem.

• Check the fuel quality.

Fuel system checks.

• Check the injection pump.

• Check the injection pump timing.

• Check the injection nozzles.

Sensor Check

• Check the engine coolant temperature sensor by using the Tech 2 in order to compare the en-

gine coolant temperature with the Ambient Air Temperature on a cold engine. If the 
coolant temperature reading is more than 5˚ more or less than Ambient Air Temperature 
on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor it-
self.

• Check the glow plug system operation.

Air intake system check.

• 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.