A/C Idle-Up System Operation

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.
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.
Enable diagnostic mode by connecting Jumper Wire (09843-18020) between terminals TE1 and E1 of DLC No. 1. See Figure. If engine speed increases and decreases as described in step 2), A/C idle-up system is okay.
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.