Chevrolet Silverado / GMC Sierra. Service manual — part 1703

Range Selector Lever Cable Adjustment (MYC 6L80E, MYD 6L90E)

Range Selector Lever Cable Adjustment (MW7 Allison)

Park/Neutral Position Switch Adjustment (M30 4L60E, M70 4L70E)

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

Starter Solenoid Cable Replacement (4.3L) or Starter Solenoid Cable Replacement
(4.8L, 5.3L, 6.0L, and 6.2L) or Starter Solenoid Cable Replacement (6.6L) or Starter
Solenoid Cable Replacement (6.2L w/Auxiliary Battery)

Clutch Pedal Engine Start Switch Replacement (TZ0 Manual)

Park/Neutral Position Switch Replacement (M30 4L60E, M70 4L70E)

Control Valve Body Assembly Removal for shift shaft position switch replacement
(MYC 6L80E, MYD 6L90E)

Control Valve Body Assembly Disassemble for shift shaft position switch replacement
(MYC 6L80E, MYD 6L90E)

Transmission Internal Mode Switch Replacement (MW7 Allison)

Starter Motor Solenoid Replacement (6.6L) 6.6L Diesel (LMM)

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

Control Module References for BCM or ECM replacement, setup and programming

STARTER SOLENOID CLICKS, ENGINE DOES NOT CRANK

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.

Circuit/System Description

When the ignition switch is placed in the START position, a discrete signal is supplied to the
body control module (BCM) notifying it that the ignition is in the START position. The BCM
then sends a serial data message to the engine control module (ECM) that crank has been
requested. The ECM monitors the park/neutral position switch and the clutch pedal position
sensor. If the transmission is in Park or Neutral, or the clutch pedal is pressed, and there are no
DTCs that inhibit engine starting, then the ECM supplies voltage to the control circuit of the
STRTR relay. When this occurs, battery voltage is supplied through the STRTR relay to the X2-S

2008 Chevrolet Silverado 1500

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

terminal of the starter solenoid. The starter solenoid energizes, and supplies battery voltage to the
starter from the B terminal to crank the engine.

Reference Information

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Starting System Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Circuit/System Verification

1. Attempt to start the engine. Verify that the starter solenoid clicks.

If the starter solenoid does not click, refer to Starter Solenoid Does Not Click.

If the engine cranks slowly, refer to Engine Cranks Slowly.

2. Go to Circuit/System Testing.

Circuit/System Testing

1. Verify that the battery is sufficiently charged and that the battery cables are clean and tight.

Refer to Charging System Test.

If the battery is not sufficiently charged, refer to Battery Charging.

If the battery cables are not clean and tight, refer to Fastener Tightening
Specifications.

2. Using a DMM, measure voltage between the positive battery terminal and X1 terminal B at

the solenoid as the ignition switch is turned to the START position. Voltage should be less

2008 Chevrolet Silverado 1500

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

than 0.5 volt.

If greater than the specified value, replace the starter solenoid cable.

3. Using a DMM, measure voltage between the negative battery terminal and the starter motor

case as the ignition switch is turned to the START position. Voltage should be less than 0.5
volt.

If greater than the specified value, replace the negative battery cable.

4. Remove the drive belt(s). Refer to one of the following:

Drive Belt Replacement for the 4.3L (LU3) engine

Drive Belt Replacement for the 6.6L Diesel (LMM) engine

Drive Belt Replacement - Accessory for all other engines (w/o LU3 or LMM)

Air Conditioning Compressor Belt Replacement for all other engines (w/o LU3 or
LMM)

5. Attempt to start the engine, with the drive belt(s) removed.

If the engine cranks, inspect the engine accessories and belt drive system for
mechanical binding.

6. Attempt to rotate the crankshaft using a breaker bar, or other suitable tool. Verify that the

engine is not seized.

If the engine is seized, refer to one of the following:

Engine Will Not Crank - Crankshaft Will Not Rotate for the 4.3L (LU3)
engine

Engine Will Not Crank - Crankshaft Will Not Rotate for the 6.6L Diesel
(LMM) engine

Engine Will Not Crank - Crankshaft Will Not Rotate for all other engines
(w/o LU3 or LMM)

7. If all circuits test normal, replace the starter motor, or the starter solenoid (LMM 6.6L

Diesel).

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Battery Charging

Starter Solenoid Cable Replacement (4.3L) or Starter Solenoid Cable Replacement
(4.8L, 5.3L, 6.0L, and 6.2L) or Starter Solenoid Cable Replacement (6.6L) or Starter
Solenoid Cable Replacement (6.2L w/Auxiliary Battery)

Battery Negative Cable Replacement (4.3L) or Battery Negative Cable Replacement

2008 Chevrolet Silverado 1500

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

(4.8L, 5.3L, 6.0L, and 6.2L) or Battery Negative Cable Replacement (6.6L)

Starter Motor Solenoid Replacement (6.6L) (LMM 6.6L Diesel)

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

ENGINE CRANKS SLOWLY

Perform the following checks:

Battery-Battery Inspection/Test. Refer to Battery Inspection/Test.

Wiring-Inspect the wiring for damage. Inspect all connections to the starter motor, solenoid,
battery, and all ground connections. Refer to Circuit Testing , Wiring Repairs , Testing
for Intermittent Conditions and Poor Connections and Connector Repairs .

Engine-Make sure the engine is not seized. Refer to Symptoms - Engine Mechanical .

If the battery, the wiring and the engine are functioning properly and the engine continues to
crank slowly, replace the starter motor. Refer to Starter Motor Replacement (4.3L) or Starter
Motor Replacement (4.8L, 5.3L, 6.0L, and 6.2L) or Starter Motor Replacement (6.6L).

STARTER MOTOR 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.

Circuit/System Description

The PG starter motors are non-repairable. They have pole pieces that are arranged around the
armature. Both solenoid windings are energized. The pull-in winding circuit is completed to the
ground through the starter motor. The windings work together magnetically to pull and hold in
the plunger. The plunger moves the shift lever. This action causes the starter drive assembly to
rotate on the armature shaft spline as it engages with the flywheel ring gear on the engine. Moving
at the same time, the plunger also closes the solenoid switch contacts in the starter solenoid. Full
battery voltage is applied directly to the starter motor and it cranks the engine.

Reference Information

Description and Operation

2008 Chevrolet Silverado 1500

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