1995 Lexus ES 300FACTORY OEM SERVICE PROCEDURE

A/C Idle-Up System Operation

  1. Ensure air hoses leading to A/C idle-up valve are not clogged. See COMPONENT LOCATIONS  under INTRODUCTION. Run engine at operating temperature. Shift transmission into Neutral. Block wheels. Ensure idle speed is 650-750 RPM. See CONNECTING TACHOMETER  under INTRODUCTION. Turn A/C on.
  2. In step 3), you will enable a diagnostic mode that causes the ECM to send signals to the A/C idle-up valve. Before enabling diagnostic mode, read the following description of what should happen after mode is enabled:
    • First 3 Seconds Full idle-up should occur, causing engine speed to increase to about 1000 RPM.
    • 3-15 Seconds Partial idle-up should occur, causing engine speed to decrease to about 700-800 RPM (at this point, record engine speed for comparison later).
    • After 15 Seconds Normal idle-up should occur, causing engine speed to increase by no more than 100 RPM.
  3. Enable diagnostic mode by connecting Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1. See Figure. I f engine speed increases and decreases as described in step 2), A/C idle-up system is okay.
  4. If engine speed does not increase and decrease as described in step 2), repair system as follows, according to time frame in which system failed test:
    • First 3 Seconds If engine speed decreased by about 100 RPM or more, or if engine idled roughly or stalled, check A/C idle-up valve. If A/C idle-up valve is okay, check for voltage at ECM. If voltage is present at ECM, replace ECM.
    • 3-15 Seconds If engine speed did not decrease as specified, check A/C idle-up valve. If A/C idle-up valve is okay, check for voltage at ECM. If voltage is present at ECM, replace ECM.
    • After 15 Seconds If engine speed increased by more than 100 RPM, adjust A/C idle-up valve as follows: Use a 4-mm hexagon wrench to turn screw on A/C idle-up valve. See Figure. Turn screw until engine speed is about 100 RPM more than engine speed that was previously recorded.
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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.