Computers and Control Systems: Adjustments

NOTE: Before performing this check:
- Verify no codes displayed.
- Idle air control system has been checked.
- Ignition timing is correct.

CONTROLLED IDLE SPEED CHECK
- Set parking brake and block drive wheels.
- Connect a SCAN tool to the assembly line data link (ALDL) connect with tool in Open Mode.
- START engine and bring it to normal operating temperature.
- Check for correct state of PARK/NEUTRAL switch on SCAN tool.
- Check specifications chart for controlled idle speed and IAC valve pintle position (counts).
- If within specifications, the idle speed is being correctly controlled by the control module.
- If not within specifications, refer to DIAGNOSIS BY SYMPTOM.

MINIMUM IDLE AIR RATE CHECK
Minimum Idle Air Rate is not adjustable on this engine.

CONTROLLED IDLE SPEED

Transmission Gear Idle Speed IAC Counts [1] OPEN/CLOSED Loop [2]


Auto D 550 5-40 CL


[1] Add 2 counts for engines with less than 500 miles. Add 1 count for every 1000 ft. above sea level.
[2] Let engine idle until proper fuel control status is reached (OPEN/CLOSED loop).