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HOMESERVICE MANUALSISUZU1985I-MARK 2D HATCHBACK, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSISFEEDBACK CARBURETOR SYSTEMTESTINGDIAGNOSTIC SYSTEM
1985 Isuzu I-Mark 2D Hatchback, Standard

Diagnostic System

1985 Isuzu I-Mark 2D Hatchback, StandardSECTION Diagnostic System

The ECM of the Closed Loop Emission Control system is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, the ECM will light the amber "CHECK ENGINE" lamp located on the instrument panel. When a malfunction is detected and lamp is turned on, a corresponding trouble code is stored in ECM memory.

As a bulb and system check, the "CHECK ENGINE" lamp will glow when ignition switch is on and engine is not running. When engine is started, the lamp should go out after 1-4 seconds. If not, a malfunction has been detected in the Closed Loop Emission system.

NOTE: Trouble codes will be recorded at various operating times. Some codes require operation of sensor or switch for 5 seconds; others require operation for 5 minutes or more.

Diagnosis of the Closed Loop Emission system is done in the following order:

  1. Ensure all engine systems NOT related to the system are fully operational. DO NOT  proceed with testing unless all other problems have been corrected. Ensure that all electrical and vacuum connections are correct and in good condition.
  2. Enter diagnostic mode and record trouble codes flashed by "CHECK ENGINE" lamp. Exit diagnostic mode.
  3. Distinguish between fixed or intermittent trouble codes.
  4. If trouble codes were displayed, go to Diagnostic Circuit Check chart. Follow instructions given in chart.
  5. If no trouble codes were recorded, go to Driver Complaint chart and follow instructions given there.
  6. After any repairs are made, perform System Performance Check. Clear any trouble codes.

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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.