Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 970 (ENGINE CONTROLS - 4.8L, 5.3L, & 6.0L (INTRODUCTION))REPAIR INSTRUCTIONSFUEL COMPOSITION SENSOR REPLACEMENT (5.3L (L59) ENGINE)INSTALLATION PROCEDURE

2003 Chevrolet TrailBlazer 4.2 S, 4WD

Installation Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Installation Procedure

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Refer to Fastener Notice in Cautions and Notices.

If required, install the fuel composition sensor to the bracket and install the bolts.
Tighten: Tighten bolts to 10 N.m (89 lb in).
Install the fuel composition sensor.
Install the fuel composition sensor nuts.
Tighten: Tighten nuts to 17 N.m (13 lb ft).

Fig 1: Fuel Composition Sensor & Nuts

Courtesy of GENERAL MOTORS CORP.

Connect the fuel pipes to the fuel composition sensor. Refer to Quick Connect Fitting(s) Service (Metal Collar) .
Install the fuel line retainers (1).

Fig 2: Fuel Line Retainers

Courtesy of GENERAL MOTORS CORP.

Connect the fuel composition sensor electrical connector.

Fig 3: Fuel Composition Sensor Electrical Connector

Courtesy of GENERAL MOTORS CORP.

Lower the vehicle.
Use the following procedure in order to inspect for leaks:
1. Turn the ignition ON, with the engine OFF, for 2 seconds.
2. Turn the ignition OFF for 10 seconds.
3. Turn the ignition ON, with the engine OFF.
4. Inspect for fuel leaks.

RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.