C 3500 Truck 2WD V8-8.1L VIN G (2001)
Camshaft Position Sensor: All Technical Service Bulletins
Electronic Ignition System - Revised Diagnosis
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 01-06-04-047
Date: November, 2001
SERVICE MANUAL UPDATE
Subject:
Revised Electronic Ignition System Diagnosis
Models:
2001 Chevrolet and GMC C/K Pickup and Utility Models
(Silverado, Sierra, Sierra Classic HD, C/K Classic HD, Suburban, Yukon XL)
2001 Chevrolet and GMC B7 Bus Chassis and C-Series Conventional Medium Duty Models
with 8.1L Engine (VIN G - RPO L18)
This bulletin is being issued to revise the Electronic Ignition System Diagnosis in the Engine Controls-8.1 L sub-section of the Service Manual. Please
replace the current information in the Service Manual with the following information.
The following information has been updated within SI2000. If you are using a paper version of this Service Manual, please make a reference to this
bulletin on the affected page.
Electronic Ignition (E1) System Diagnosis
Circuit Description
The electronic ignition system uses an individual ignition coil for each cylinder. The powertrain control module (PCM) controls the ignition operation
through eight individual ignition control (IC) circuits. Each bank of tour ignition coils is connected to the PCM, power, or ground by the following
circuits:
^
Low reference
^
Chassis ground
^
Ignition 1 voltage
^
The appropriate IC circuit
The PCM triggers an ignition coil by grounding the appropriate IC circuit using information from the crankshaft position (CKP) and camshaft position
(CMP) sensors.
Diagnostic Aids
Important:
A missing CMP sensor signal may cause a long crank condition.
The CKP signal must be available for the engine to start. The CMP signal is not needed to start and operate the engine. The PCM can determine when a
cylinder is on either the firing or exhaust stroke by the 24X signal.
The 12 volt reference circuit for the CKP and CMP sensors are shared internally in the PCM.
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the
PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
For an intermittent condition, refer to Intermittent Conditions.
