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 DIAGNOSISENGINE MECHANICALELECTRIC COOLING FANSDIAGNOSTIC TESTSDTC P0495TEST DESCRIPTION

2003 Chevrolet TrailBlazer 4.2 S, 4WD

Test Description

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description

The numbers below refer to the test step numbers.

2)

This step ensures that the DTC has failed this ignition cycle. If the scan tool displays Passed, then the answer is No.

3)

The cooling fan noise should increase as the cooling fan engages. It can take up to 2 minutes for full cooling fan engagement. If cooling fan is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, then answer Yes.

4)

In the previous step the cooling fan was fully engaged. This step tests to ensure that the cooling fan will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan and a disengaged cooling fan. The cooling fan is completely disengaged when the excessive fan noise is not heard.

5)

Tests the ability of the PCM to control the cooling fan speed. If answer to question is Yes, see DIAGNOSTIC AIDS .

6)

Disconnecting the cooling fan and running the engine ensure that the cooling fan is not engaged. When rotating the cooling fan it should spin freely. If not then the cooling fan will not disengage.

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.