GM 4.2L Index of Articles

Ignition System Wiring Diagram (2002-2005 4.2L Chevrolet TrailBlazer)

Ignition System Wiring Diagram (2002-2005 4.2L Chevrolet TrailBlazer)

The following simplified ignition system wiring diagrams include the coil-on-plug (COP) ignition coils, camshaft position sensor, crankshaft position sensor, and the knock sensor circuits. Applies to the 2002, 2003, 2004, 2005 4.2L Chevrolet...   read more >>

How To Test The Ignition Coils (2002-2005 4.2L Chevrolet TrailBlazer)

How To Test The Ignition Coils (2002-2005 4.2L Chevrolet TrailBlazer)

In this tutorial I'm going to explain how to test the ignition coils on the 2002, 2003, 2004, and 2005 4.2L Chevrolet TrailBlazer and GMC Envoy. Testing the ignition coils, to find out if you have a defective one, isn't hard and I'll explain how...   read more >>

How To Test The MAP Sensor (2002-2007 4.2L Chevrolet Trailblazer)

How To Test The MAP Sensor (2002-2007 4.2L Chevrolet Trailblazer)

This tutorial will help you to test the manifold absolute pressure (MAP) sensor on the 2002-2007 4.2L Chevrolet TrailBlazer or GMC Envoy. All you'll need to test it is a vacuum pump and a multimeter. Now if you don't have a vacuum pump, don't...   read more >>

TAC System Wiring Diagram (2006-2007 4.2L Chevrolet TrailBlazer)

TAC System Wiring Diagram (2006-2007 4.2L Chevrolet TrailBlazer)

The throttle actuator control (TAC) system is made up of the following: APP Sensor 1, APP Sensor 2, TPS 1, TPS 2, Throttle Actuator Motor. This simplified wiring diagram includes the electronic throttle body circuit diagram and the APP sensor...   read more >>

How To Test APP Sensor 1 And 2 (2002-2003 4.2L Chevrolet TrailBlazer)

How To Test APP Sensor 1 And 2  (2002-2003 4.2L Chevrolet TrailBlazer)

In this tutorial I'm going to explain how to test accelerator pedal position (APP) sensor 1 and sensor 2. Testing both of these APP sensors simply involves testing the resistance between two terminals as the pedal is depressed and...   read more >>

Camshaft Position Actuator Solenoid Test (2002-2009 4.2L Chevrolet TrailBlazer)

Camshaft Position Actuator Solenoid Test (2002-2009 4.2L Chevrolet TrailBlazer)

In this tutorial I'm going to be showing you how to test the camshaft position actuator solenoid. The exact same camshaft position actuator solenoid is used on the 2002 through 2009 4.2L Chevrolet TrailBlazer and GMC Envoy. With your test...   read more >>

Electronic Throttle Body Tests (2002-2007 4.2L Chevrolet TrailBlazer)

Electronic Throttle Body Tests (2002-2007 4.2L Chevrolet TrailBlazer)

This tutorial will explain how to test the electronic throttle body on the 2002-2007 4.2L Chevrolet TrailBlazer and GMC Envoy. You'll be able to find out if TPS 1 or TPS 2 is defective or not. We'll also test the throttle actuator motor. You...   read more >>

How To Test Camshaft Position Sensor (2002-2005 4.2L Chevrolet Trailblazer)

How To Test Camshaft Position Sensor  (2002-2005 4.2L Chevrolet Trailblazer)

In this tutorial I'm going to show you how to test the camshaft position sensor, on the 2002-2005 4.2L Chevrolet TrailBlazer and GMC Envoy, using a multimeter in Volts DC mode. With your multimeter test results will be able to accurately...   read more >>

TAC System Wiring Diagram (2002-2005 4.2L Chevrolet TrailBlazer)

TAC System Wiring Diagram (2002-2005 4.2L Chevrolet TrailBlazer)

Here's a simplified throttle actuator control (TAC) system wiring diagram. Includes the electronic throttle body circuit diagram and the APP sensor assembly circuit diagram. Contents of this tutorial: DIAGRAM 1: Electronic...   read more >>

How To Test APP Sensor 1 And 2 (2004-2007 4.2L Chevrolet TrailBlazer)

How To Test APP Sensor 1 And 2 (2004-2007 4.2L Chevrolet TrailBlazer)

Testing APP sensor 1 and APP sensor 2 on the 2004-2007 4.2L Chevrolet TrailBlazer or GMC Envoy is something that can be done easily with just a multimeter. In this tutorial I will explain how to do it in a step-by-step way so that you can find...   read more >>