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Hummer H1 (2006+). Manual - part 27

2-14

Engine

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Oil leaks at:

• Rocker covers

• Oil pan

• Rear main seal

• Oil filter

• Timing gear cover or seal

• Cooler hoses/lines

Locate and correct leaks as needed.

Engine problem:

• Worn broken piston rings

• Worn valve seats or guides

Run compression test to verify ring problem.
Overhaul cylinder heads if guides, seals or valves
are worn. If wear is premature, check injectors
and injection pump. Excessive fuel will wash oil
off walls/guides causing ring and valve wear.

Engine
Vibration

NOTE: See
road test infor-
mation in this
section.

Loose engine accessories:

• Alternator

• A/C compressor

• Power steering pump

• Mounting brackets

• Pulleys

• Belt tensioner

• Serpentine belt

• Drive pulleys

Check and repair as needed. Replace damaged
missing bolts and apply Loctite 242 to loose bolt
threads. Replace serpentine belt if damaged.
Replace bent or broken pulleys.

Torsional damper damaged or loose.

Replace damper if damaged, worn or loose.

Flywheel (driveplate) cracked or loose.

Replace flywheel and also check for ballooned or
damaged converter.

Torque converter imbalance caused by
internal damage or missing balance weight.

Replace converter.

Overheating

Dirt, debris blocking air flow through cool-
ers, condenser and radiator.

Remove and clear fins with compressed air, soft
bristle brush or water stream.

Low coolant level.

Add coolant and check for leaks (hoses, surge
tank, hose connections, water pump and radiator).

Serpentine belt loose, worn or tensioner
inoperative.

Replace belt and/or tensioner if either part has
failed or is worn beyond limit.

Prolonged idling/slow speed operation in
heavy traffic when ambient temperatures are
high.

If this type operation cannot be avoided, have
driver turn on heater and “rev” engine when
stopped in traffic. This will help dissipate some
heat and get more air through radiator (from fan).

Failed thermostat or radiator cap.

Check thermostat and cap operation. Replace
either part if inoperative.

Geared fan drive inoperative.

Replace geared fan drive.

Water pump inoperative.

Check coolant flow and replace pump if neces-
sary.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

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Engine 2-15

5745804

TURBOCHARGER SERVICE AND DIAGNOSIS

Description

The turbocharged diesel engine is equipped with an IHI turbocharger. Vanes in the turbine housing control the boost. The position
of the vanes is variable and controlled by a vain position solenoid based on information sent to the ECM by the boost sensor. The
vane position is monitored by the vane position sensor. This allows a proportionate increase in fuel injected into the cylinders. The
result is a much denser cylinder charge and greater power output.

The turbocharger turbine and compressor impellers are the mechanisms that pump additional air into the combustion chambers.
The impeller wheels are operated by the high speed gas flow through the engine exhaust system.

The turbocharger is mounted in the lifter valley at the rear of the engine block. It is positioned between the two halves of the intake
manifold.

A turbocharger is fundamentally an air pump used to generate additional engine power. This is accomplished by increasing volume
and pressure of air entering the engine combustion chambers. An increase in air volume allows a proportional increase in fuel in-
jected into the cylinders. The net result is a denser fuel/air mixture. A denser mixture produces more power when compressed and
burned in the combustion chamber.

A turbocharger feature concerns the method of operation. The turbocharger turbine and compressor impellers are rotated by the
flow of engine exhaust gases. As a result, separate drive belts and pulleys are not needed.

The turbocharger used on 6.6L engines consists of a turbine impeller and housing, a compressor impeller and housing, turbo-
charger vanes, vane position sensor, vane position control solenoid valve, vane position unison ring, hydraulic piston, cam and an
impeller connecting shaft (Figure 2-5).

Blown head gasket.

Verify that coolant is leaking into combustion
chamber and replace gasket.

Crack in block or leaking freeze plug.

Replace corroded freeze plugs. Replace block if
cracked.

10. Coolant temperature gauge or sensor faulty.

10. Test and replace gauges or sensors as needed.

High Fuel
Consumption

Prolonged high speed - high load operation.

Normal with this type of operation. Have driver
reduce speed or load if possible.

Air cleaner/filter partially plugged.

Remove and clean air horn, intake hose and air
cleaner. Replace filter.

Fuel leaks in lines, hoses at connections.

Locate and repair as needed.

Restriction in exhaust system (should also
be accompanied by drop in power).

Inspect and replace bent, kinked or damaged com-
ponents.

Decrease in boost on turbocharged models,
caused by manifold leak or turbo damage.

Correct leaks. Replace turbocharger if inopera-
tive.

Brake drag.

Repair stuck/seized calipers.

Converter one way clutch failure.

Replace converter.

Injection pump internal problem.

Diagnose and replace as necessary.

Power loss due to worn rings, valve guides,
cylinder bores, valves, etc.

Overhaul engine.

Engine Diagnosis

PROBLEM

POTENTIAL CAUSE

CORRECTION

2-16

Engine

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Figure 2-5: Turbocharger Components (Typical)

Turbocharger Operation

The turbocharger increases engine power by pumping compressed air into the combustion chambers, allowing a greater quantity of
fuel to combust at the optimal air/fuel ratio. In a conventional turbo, the turbine spins as exhaust gas flows out of the engine and
over the turbine blades. This spins the compressor wheel at the other end of the turbine shaft, pumping more air into the intake sys-
tem. The turbocharger for this system has vane position control by the engine control module (ECM). The vanes can be opened and
closed to vary the amount of boost pressure. The boost pressure can be controlled independent of the engine speed. There are con-
trollable vanes in the turbocharger. The vanes mount to a unison ring that can be rotated to change the vane angle. When the engine
is not under load, the vanes are open to minimize boost and the exhaust back pressure. To increase boost when the engine load re-
quires it, the vanes are commanded closed. The ECM will vary the boost dependent upon the load requirements of the engine. The
turbocharger vanes are normally open when the engine is not under load. However, the ECM will often close the turbocharger
vanes to create back pressure to drive the exhaust gas through the exhaust gas recirculation (EGR) valve as required. At extreme
cold temperatures, the ECM may close the vanes at a low load conditions in order to accelerate the engine coolant heating.

TURBOCHARGER LEARN PROCEDURE

Description

The turbocharger (TC) learns the vane positions automatically during each ignition cycle. The engine control module (ECM) per-
forms the turbocharger learn procedure automatically when the enable criteria are met. After each ignition cycle, and before the en-
able criteria ha been met, the ECM will use the previously learned value. If the ECM does not have a previously learn value, it will
default to a stored calibrated value. The ECM will use this value until the enable criteria have been met. It will then perform this
procedure to learn the new value. If the ECM attempts to perform the learn procedure and fails, DTCsþP0046 or P2563 may set.

The turbocharger learn procedure must be performed manually with a Techþ2 when any turbocharger system service has been per-
formed. Certain enable criteria must be met for the ECM to perform this procedure.

TURBOCHARGER

VANE POSITION

SENSOR

TURBOCHARGER

VANE POSITION

CONTROL SOLENOID

VALVE

TURBOCHARGER

VANE POSITION

UNISON RING

TURBINE

TURBOCHARGER

VANES

HYDRAULIC

PISTON

CAM

11-1-05

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Engine 2-17

5745804

The turbocharger learn procedure is required when the following service procedures have been performed:

• The turbocharger vane position control solenoid valve replacement

• The turbocharger vane position sensor replacement

• The engine control module (ECM) replacement

• The turbocharger replacement

• Any service that disturbs the turbocharger components

Learn Procedure

NOTE: Once the enable conditions have been met the throttle must remain at idle. Do not change the accelerator pedal position
(APP) during this procedure.

The following conditions must be met for the ECM to perform the turbocharger learn procedure:

• The A/C is OFF.

• The vehicle is in Park or Neutral.

• Start and idle the engine.

• The engine coolant temperature (ECT) is more than 104°F (40°C).

After the enable conditions have been met and the engine idle is stabilized, enter the TC Learn Output function from the Engine
Output Control Menu. Command the TC Vane Position Sensor ON for at least 5þseconds, then command it OFF. The system
should have learned the new turbocharger position. The TC Learned parameter should have toggled from No to Yes.

Electronic Accelerator Pedal

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of 3þin-
dividual sensors within one housing. Three separate signal, low reference, and 5-volt reference circuits are used in order to inter-
face the accelerator pedal sensor assembly with the ECM. Each sensor has a unique functionality to determine pedal position. The
ECM uses the APP sensor to determine the amount of acceleration or deceleration desired by the person driving the vehicle. The
APP sensorþ1 voltage should increase as the accelerator pedal is depressed, from below 1.0þvolt at 0þpedal travel to above 2þvolts
at 100þpercent pedal travel. APP sensorþ2 voltage should decrease from above 4þvolts at 0þpedal travel to below 3.0þvolts at
100þpercent pedal travel. APP sensorþ3 voltage should decrease from above 3.8þvolts at 0þpercent pedal travel to below 3.3þvolts
at 100þpercent pedal travel (Figure 2-6).

Figure 2-6: Electronic Accelerator Pedal

PEDAL AND

ARM

MOUNTING

BRACKET

POSITION
SENSORS

11-1-05

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