Computers and Control Systems: Adjustments

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

PROCEDURE
- 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 ECM.
- If not within specifications, refer to DIAGNOSIS BY SYMPTOM/DIAGNOSIS AND TESTING PROCEDURES/ROUGH, UNSTABLE OR INCORRECT IDLE.

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]

Man. N 900 5-20 CL

Auto D 800 15-40 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).