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 MANUALSCHEVROLET1987CHEVETTE L4-98 1.6LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSTESTING AND INSPECTIONINITIAL INSPECTION AND DIAGNOSTIC OVERVIEWDIAGNOSTIC CIRCUIT CHECK
1987 Chevrolet Chevette L4-98 1.6L
Diagnostic Circuit Check
1987 Chevrolet Chevette L4-98 1.6LSECTION Diagnostic Circuit Check
Fig. 010 - Procedure for Diagnostic Circuit Check VIN C:
1982-87 VIN C (1.6L)
The purpose of the Diagnostic Circuit Check is to:
a. Make sure the "CHECK ENGINE" lamp is working.
b. The ECM is operating and can recognize a fault. This is the starting point for any diagnosis. If there are no trouble codes indicated, go to the System Performance Check. If no additional checks are called out from the System Performance Check, go to the Driveability Symptom in Section "B."
Fig. 009 - Chart - Diagnostic Circuit Check:
1. This checks the "CHECK ENGINE" lamp circuit. Normal operation is when "CHECK ENGINE" lamp is "on" steady.
2. This checks to see if the ECM can recognize a fault. Because the engine is not running, then there is no reference pulse and light should flash trouble code 12.
3. This checks to see if there is a problem that will set a code at curb idle for one minute.
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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.