1989 Mitsubishi Precis BaseFACTORY OEM SERVICE PROCEDURE

Control Unit

NOTE: For ease of understanding, components are grouped into 2 categories. The first category, INPUT DEVICES, is components which control or produce voltage signals that are monitored by the ECU. The second category, OUTPUT DEVICES, are components that are controlled by the ECU (this is usually accomplished by the ECU grounding individual circuits).

The ECU (Electronic Control Unit) is an 8-bit microprocessor with Random Access Memory (RAM) and Read Only Memory (ROM). An input/output interface converts incoming sensor signals to values the processor can utilize to determine engine conditions and direct various output actuators. Main actuators are the Feedback Solenoid Valve (FBSV) and the Slow-Cut Solenoid Valve (SCSV).

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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.