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 438 (ENGINE CONTROLS - TROUBLE SHOOTING - NO CODES)SYMPTOMSCUTS OUT, MISSESSENSOR/SYSTEM CHECKS
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Sensor/System Checks
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Sensor/System Checks
WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
- Check Mass Airflow (MAF) sensor and connections.
- Check the Engine Coolant Temperature (ECT) sensor for being shifted in value. Connect the scan tool and compare the ECT with the Intake Air Temperature (IAT) sensor on a cold engine. The ECT and IAT should be within 5°F of each other. Check the resistance of the ECT sensor if the temperature is out of range with the IAT sensor. See TEMPERATURE VS RESISTANCE table for specifications.
- Check Throttle Position (TP) sensor and connections. See DTC P0121: THROTTLE POSITION SENSOR CIRCUIT INSUFFICIENT ACTIVITY under DIAGNOSTIC TESTS in SELF-DIAGNOSTICS - 4.0L AURORA article.
- Check for throttle body tampering, excessive deposits, or damage.
- Check the Exhaust Gas Recirculation (EGR) system for proper operation. See EXHAUST GAS RECIRCULATION under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4.0L AURORA article.
TEMPERATURE VS RESISTANCE
| Temperature - °F (°C) | (1) Ohms | ||
|---|---|---|---|
| 302 (150) | 47 | ||
| 266 (130) | 77 | ||
| 230 (110) | 132 | ||
| 194 (90) | 241 | ||
| 158 (70) | 467 | ||
| 122 (50) | 973 | ||
| 104 (40) | 1459 | ||
| 86 (30) | 2238 | ||
| 68 (20) | 3520 | ||
| 50 (10) | 5670 | ||
| 32 (0) | 9420 | ||
| 14 (-10) | 16,180 | ||
| -4 (-20) | 28,680 | ||
| -40 (-40) | 100,700 | ||
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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.