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 355 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L BI-FUEL)DIAGNOSTIC TESTSDTC P1020: FUEL INJECTOR CONTROL CIRCUITTEST DESCRIPTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD
Test Description
2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Test Description
WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedure.
- 2 - The step determines if the condition exists. When DTC P1020 sets, the vehicle will switch over to gasoline operation.
- 4 - The step determines if the condition affects CNG and gasoline operation.
- 5 - This step tests the fuel injector control circuit from the PCM to the AF injector relay. If the test light blinks, the PCM and wiring are okay.
- 6 - This step determines if a ground is constantly applied to the fuel injector control circuit.
- 8 - This step tests the fuel injector signal circuit from the FICM. If the test light illuminates, the FICM and wiring are okay.
- 9 - This step isolates the inoperative AF injector relay. Remove the AF injectors from the mounting bracket to prevent misdiagnosis.
- 10 - This step tests the ignition voltage circuits to each AF injector relay coil.
- 11 - This step tests the ground circuits to each AF injector relay coil.
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.