Chevrolet Silverado / GMC Sierra. Manual

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Auxiliary Battery Relay Replacement (6.2L)

Auxiliary Generator Replacement (6.6L)

Battery Positive Cable Fuse Replacement (w/Single Battery) or Battery Positive
Cable Fuse Replacement (w/Auxiliary Battery)

Generator Replacement (4.3L) or Generator Replacement (4.8L, 5.3L, 6.0L, and
6.2L) or Generator Replacement (6.6L)

Generator Battery Jumper Cable Replacement

Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an
Electrical Center)

GENERATOR NOISE DIAGNOSIS

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Aids

Noise from a generator may be due to electrical or mechanical noise. Electrical noise or magnetic
whine usually varies with the electrical load placed on the generator and is a normal operating
characteristic of all generators. When diagnosing a noisy generator, it is important to remember
that loose or misaligned components around the generator may transmit the noise into the
passenger compartment and that replacing the generator may not solve the problem.

Circuit/System Testing

1. Start the engine. Verify the noise can be heard. Compare the concern to a similar vehicle.

2. Perform a charging system test. Verify that the generator is charging properly. Refer to

Charging System Test.

If the battery is discharged, charge the battery.

If the generator fails the charging system test, replace the generator.

3. Verify that the power steering fluid level is not low, if equipped. Refer to Checking and

Adding Power Steering Fluid (With Hydroboost) or Checking and Adding Power
Steering Fluid (Without Hydroboost) or Checking and Adding Power Steering Fluid
(With Hydroboost) or Checking and Adding Power Steering Fluid (Without

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Electrical - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Hydroboost) .

If the power steering fluid level is low, go to Power Steering Fluid Leaks .

4. Inspect the generator, generator mounting, wiring harness, heater hoses, A/C lines, or other

accessory equipment that may be misrouted or be the cause of noise being transmitted into
the passenger compartment.

5. Ignition OFF, remove the engine drive belt(s). Refer to one of the following:

Drive Belt Replacement 4.3L (LU3)

Drive Belt Replacement 6.6L (LMM)

Drive Belt Replacement - Accessory all others (w/o LU3 or LMM)

Air Conditioning Compressor Belt Replacement all others (w/o LU3 or LMM)

6. Verify the generator, A./C compressor (if equipped), water pump pulley, power steering

pump (if equipped), idler pulley(s), and tensioner pulley(s) spin freely, and that the pully
bearings are not loose.

If any of the pulleys do not spin freely, or has a loose bearing, replace the affected
component.

7. Start the engine, with the drive belt(s) removed. Verify that the noise goes away. Operate

the engine for no longer than 30 seconds.

If the noise is still present, the generator is not the cause of the noise.

8. Loosen all generator mounting bolts and ensure the generator is properly aligned. Tighten

the mounting bolts to specification, refer to Generator Replacement (4.3L) or Generator
Replacement (4.8L, 5.3L, 6.0L, and 6.2L) or Generator Replacement (6.6L).

9. If the noise is still present, replace the generator.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Generator Replacement (4.3L) or Generator Replacement (4.8L, 5.3L, 6.0L, and 6.2L) or
Generator Replacement (6.6L)

STARTER SOLENOID DOES NOT CLICK

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Electrical - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Diagnostic Fault Information

Circuit/System Description

The engine control module (ECM) controls engine cranking based on a power mode input and the
status of the park/neutral position (PNP) switch or clutch pedal position sensor. With the
transmission in Park/Neutral, voltage at the ECM PNP switch signal circuit is low. This indicates
to the ECM that conditions are acceptable for cranking. When a power mode crank request is
seen, the ECM applies voltage to the starter relay coil control circuit. This energizes the coil side
of the relay, which pulls the switch side of the relay closed, applying voltage to the starter X2-S
terminal and engaging the starter solenoid.

Reference Information

Schematic Reference

Starting and Charging Schematics

PSD SIE TITLE Error: SIE linked to empty Cell ID 167881 (TZ0 Manual)

Automatic Transmission Controls Schematics (M30 4L60E, M70 4L70E)

Automatic Transmission Controls Schematics (MYC 6L80E, MYD 6L90E)

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

Underhood Fuse Block B+

175 A MEGA Fuse

STRTR Fuse 60 (LMM) or 64
(w/o LMM)

Park Neutral Signal
(Automatic)

Clutch Pedal Position Signal
(TZ0 Manual)

P0807

P0808

P0806

Starter Relay Coil Control

Starter Solenoid Crank
Voltage

Underhood Fuse Block
Ground

1. No crank
2. Cranks in any gear
3. Cranks all the time

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Electrical - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Automatic Transmission Controls Schematics (MW7 Allison)

Connector End View Reference

Component Connector End Views

Description and Operation

Starting System Description and Operation

Electrical Information Reference

Testing for Intermittent Conditions and Poor Connections

Circuit Testing

Wiring Repairs

Connector Repairs

Scan Tool Reference

Control Module References for Scan Tool Information

Diagnostic Aids

Inspect the STRTR Fuse 60 (LMM) or 64 (w/o LMM), and the 175 A MEGA Fuse for an
open.

A misadjusted PNP switch (M30 4L60E, M70 4L70E) or range selector lever cable
(automatic) may result in a starter solenoid does not click condition.

Circuit/System Verification

1. Ignition ON, transmission in Park or Neutral. Observe the PNP Switch parameter with a

scan tool, in Engine Control Module, Data Display, Engine Data. Verify that the scan tool
PNP Switch parameter is Park/Neutral (automatic only).

If the scan tool PNP Switch parameter is not Park/Neutral, refer to Circuit/System
Testing: PNP Switch Circuit Malfunction below.

2. Command the Starter Relay ON with the scan tool, or turn the ignition switch to the START

position. The starter solenoid should engage and the engine should crank.

If the solenoid does not engage, refer to Circuit/System Testing: STRTR Relay Circuit
Malfunction below.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Electrical - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

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Chevrolet Silverado / GMC Sierra. Manual - part 1701