1990 Mazda B2600i Base, 2D PickupFACTORY OEM SERVICE PROCEDURE

System Inspection

  1. Check vacuum hoses for correct routing, clogging or leaking. Repair or replace as necessary. Warm engine to normal operating temperature and allow to idle. Disconnect vacuum hose from EGR control valve and plug hose. If engine does not run smooth, check EGR control valve.
  2. Connect vacuum gauge to hose removed from EGR control valve. Verify gauge shows no vacuum with engine at idle speed. Accelerate engine and verify gauge shows vacuum. Decelerate engine. Verify gauge again shows no vacuum. If problem is found, check duty solenoid valve and ECU terminals 2L and 2K. See PIN VOLTAGE CHART S and SENSOR RANGE CHARTS articles.
  3. With vacuum hose connected to EGR control valve, connect vacuum gauge into hose with "T" fitting. Accelerate engine and note amount of vacuum. Disconnect vacuum hose from EGR valve and plug it. Accelerate engine. If gauge does not show higher vacuum reading, check EGR position sensor, duty solenoid valve and terminal 1F of ECU. See PIN VOLTAGE CHART S and SENSOR RANGE CHARTS articles.
  4. Disconnect vacuum hose from EGR control valve and plug hose. Disconnect coolant temperature switch connector. See Figure . Connect a jumper wire across switch connector. Accelerate engine. If gauge shows vacuum, check duty solenoid valve and ECU terminal 1Q. See PIN VOLTAGE CHART S and SENSOR RANGE CHARTS articles. Reconnect temperature switch electrical connector and EGR vacuum hose.
Factory Service Tools

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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.