GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Terraza Ext. 🢒 Engine 🢒 Engine Controls - 3.9L 🢒 Electronic Ignition (EI) System Diagnosis

Diagnostic Fault Information

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

Circuit/System Description

There are 3 dual-tower ignition coils that are part of the ignition control module (ICM). The ICM contains coil driver circuits that command the coils to operate. The ICM has the following circuits:

    • An ignition voltage circuit
    • A ground
    • An ignition control (IC) 1 control circuit for the 1-4 ignition coil
    • An IC 2 control circuit for the 2-5 ignition coil
    • An IC 3 control circuit for the 3-6 ignition coil
    • A low reference circuit

The engine control module (ECM) controls each dual-tower ignition coil by transmitting timing pulses on the ignition coil control circuit to the ICM for the proper coil to enable a spark event.

Diagnostic Aids

Inspect the spark plug wires for proper orientation.

Reference Information
    •  Electronic Ignition (EI) System Description
    •  Ignition System Specifications

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Connector End Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

    •  Electrical Center Identification Views
    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Special Tools Required

    • J 26792 Spark Tester
    • J 43244 Relay Puller Pliers

Circuit/System Testing
  1. With the ignition OFF, remove the fuel pump relay using the J 43244 .
  2. Crank the engine and test for a strong spark on each cylinder spark plug wire using the J 26792 . Ground the companion cylinder spark plug wire of each cylinder when it is tested.
    3. ⇒If a strong bright blue spark is present on all 6 of the cylinders, remove and inspect all of the spark plugs for proper torque, proper gap, wear, damage, and fouling. Refer to Spark Plug Replacement , Spark Plug Inspection , and Ignition System Specifications . Replace the spark plugs if necessary.
    ⇒If there is no spark on any of the cylinders, test the ignition voltage circuit of the ICM for an open/high resistance or short to ground, or test the ground circuit of the ICM for an open/high resistance, or a faulty ICM. The wire circuit resistance should measure less than 3 ohms.
    ⇒If there is no spark on any of the cylinders, or spark is weak or intermittent, test the IC circuit for an open/high resistance, or a faulty ICM. The wire circuit resistance should measure less than 3 ohms.
    ⇒If spark is present on one or more of the cylinders, inspect and test the spark plug wires for arching, cuts, rubbing on other components, and proper resistance. Refer to Spark Plug Wire Inspection and Ignition System Specifications , or a faulty ICM.
    ⇒If all tests are normal, then the system is operating correctly.

Component Testing
    • With positive polarity to the low reference terminal, measure for 9,000-11,000 ohms at 20-23°C (68-74°F) room temperature between each of the ignition coil control terminals and the low reference terminal of the ICM.
       ⇒If the resistance is not within the specified range, replace the ICM.
    • Measure for 7,000-15,000 ohms at 20-23°C (68-74°F) room temperature between each pair of coil towers on the ICM.
       ⇒If the resistance is not within the specified range, replace the ICM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Spark Plug Wire Replacement for spark plug wire replacement
    •  Spark Plug Replacement for spark plug replacement
    •  Ignition Coil Replacement for ICM and coil assembly replacement