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 VARIANT/TRIMSECTION 2 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS - 5.3L)SELF-DIAGNOSTIC SYSTEMINTERMITTENT CONDITIONSELECTROMAGNETIC INTERFERENCE AND ELECTRICAL NOISE
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Electromagnetic Interference and Electrical Noise
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Electromagnetic Interference and Electrical Noise
WARNING: This page is about a different variant/trim than selected.
Some electrical components or circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Perform the following procedures:
- Inspect for a misrouted harness that is too close to a high voltage or high current device. This condition may induce electrical noise on a circuit that could interfere with normal circuit operation. Inspect for wires that are too close to the following devices:
- Secondary ignition components.
- Motors.
- The generator.
- Determine whether the electrical system interference is caused by a malfunctioning relay, PCM driven solenoid or switch. These components may cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating.
- Determine whether non-factory or aftermarket add-on accessories are installed in the vehicle. These accessories may lead to an emission related OBD-II failure. Determine if any of the following non-factory or aftermarket add-on accessories is causing the intermittent:
- Lights.
- 2-way radios.
- Amplifiers.
- Electric motors.
- Remote starters.
- Alarm systems.
- Cell phones.
- Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
- Test for proper performance of the generator. See ON-VEHICLE TESTING in appropriate GENERATORS & REGULATORS article in ELECTRICAL.
- If a DTC is determined to be intermittent, and the tests in this section do not reveal a problem, see VEHICLE DATA RECORDER .
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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.