Chevrolet Silverado / GMC Sierra. Manual — part 1875

The fourth through ninth digits are the last 6 digits of the VIN.

DIAGNOSTIC INFORMATION AND PROCEDURES

DIAGNOSTIC STARTING POINT - ENGINE MECHANICAL

Begin the system diagnosis by reviewing the Disassembled Views, Engine Content
Specifications, Engine Component Description, Lubrication Description (RPO LY2) or
Lubrication Description (RPO LH6/LMG/LY5/LC9) or Lubrication Description (RPO
LY6/L92) or Lubrication Description (RPO L76), Camshaft Position Actuator and
Solenoid Valve Description, and Cylinder Deactivation (Active Fuel Management) System
Description. Reviewing the description and operation information helps you determine the
correct symptom diagnostic procedure when a malfunction exists. Reviewing the description and
operation information also helps you determine if the condition described by the customer is
normal operation. Refer to Symptoms - Engine Mechanical in order to identify the correct
procedure for diagnosing the system and where the procedure is located.

SYMPTOMS - ENGINE MECHANICAL

Strategy Based Diagnostics

1. Perform the Diagnostic System Check - Vehicle before using the symptom tables.

2. Review the system operations in order to familiarize yourself with the system functions.

Refer to Disassembled Views, Engine Content Specifications, Engine Component
Description, Lubrication Description (RPO LY2) or Lubrication Description (RPO
LH6/LMG/LY5/LC9) or Lubrication Description (RPO LY6/L92) or Lubrication
Description (RPO L76), Camshaft Position Actuator and Solenoid Valve
Description, and Cylinder Deactivation (Active Fuel Management) System
Description.

All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform
approach for repairing all systems. The diagnostic flow may always be used in order to resolve a
system condition. The diagnostic flow is the place to start when repairs are necessary. For a
detailed explanation, refer to Strategy Based Diagnosis .

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the engine. Refer to
Checking Aftermarket Accessories .

Inspect the easily accessible or visible system components for obvious damage or conditions

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

which could cause the symptom.

Inspect for the correct oil level, proper oil viscosity, and correct filter application.

Verify the exact operating conditions under which the concern exists. Note factors such as
engine RPM, ambient temperature, engine temperature, amount of engine warm-up time,
and other specifics.

Compare the engine sounds, if applicable, to a known good engine and make sure you are
not trying to correct a normal condition.

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system
is operating properly.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:

Base Engine Misfire without Internal Engine Noises

Base Engine Misfire with Abnormal Internal Lower Engine Noises

Base Engine Misfire with Abnormal Valve Train Noise

Base Engine Misfire with Coolant Consumption

Base Engine Misfire with Excessive Oil Consumption

Engine Noise on Start-Up, but Only Lasting a Few Seconds

Upper Engine Noise, Regardless of Engine Speed

Lower Engine Noise, Regardless of Engine Speed

Engine Noise Under Load

Engine Will Not Crank - Crankshaft Will Not Rotate

Coolant in Combustion Chamber

Coolant in Engine Oil

Cylinder Deactivation (Active Fuel Management) System Diagnosis

Engine Compression Test

Cylinder Deactivation (Active Fuel Management) System Compression Test

Cylinder Leakage Test

Oil Consumption Diagnosis

Oil Pressure Diagnosis and Testing

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Cylinder Deactivation (Active Fuel Management) Oil Pressure Relief Valve
Diagnosis and Testing

Cylinder Deactivation (Active Fuel Management) Valve Lifter Oil Manifold
Diagnosis and Testing

Camshaft Position Actuator and Solenoid Valve Diagnosis and Testing

Oil Leak Diagnosis

Crankcase Ventilation System Inspection/Diagnosis

Drive Belt Falls Off and Excessive Wear Diagnosis

Drive Belt Tensioner Diagnosis

BASE ENGINE MISFIRE WITHOUT INTERNAL ENGINE NOISES

Cause

Correction

Fuel injector harness connectors are
connected to the incorrect fuel
injectors/cylinders

Relocate the fuel injector harness connectors,
as necessary.

Abnormalities, such as severe cracking,
bumps, or missing areas in the accessory drive
belt
Abnormalities in the accessory drive system
and/or components may cause engine RPM
variations and lead to a misfire diagnostic
trouble code (DTC). A misfire code may be
present without an actual misfire condition.

Replace the drive belt. Refer to Drive Belt
Replacement - Accessory .

Worn, damaged, or mis-aligned accessory
drive components or excessive pulley runout
May lead to a misfire DTC.
A misfire code may be present without an
actual misfire condition.

Inspect the components and repair or replace,
as required.

Loose or improperly installed engine flex
plate or crankshaft balancer
A misfire code may be present without an
actual misfire condition.

Repair or replace the flex plate and/or
balancer, as required. Refer to Automatic
Transmission Flex Plate Replacement , or
Crankshaft Balancer Replacement .

Restricted exhaust system
A severe restriction in the exhaust flow can

Repair or replace, as required.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado