Reading Measuring Block (ECM "A")

• Only the values in display field 7 are used to check A/C auxiliary signal (idle speed boost) and/or A/C compressor cut-out signal
• CO level cannot be adjusted using CO fuel trim potentiometer.
• Leave PCV hoses connected to valve covers.

Ensure engine temperature is at least 185°F (85°C). Turn A/C on. Enter self-diagnostics. See ENTERING SELF-DIAGNOSTICS. Select function 08. Select display group number 00. Check value displayed in sector 7. If value is not 20, A/C switch is on, A/C compressor is on, CTP switch is open or transmission is not in Park (Neutral on M/T).