Idle Control System: Notes
Idle speed is controlled by ECU through AAC valve and Fast Idle Control Device (FICD) valve on G20 and M30. ECU controls idle speed components based upon signals received from various input devices. If idle speed components test correctly but idle speed is not being regulated properly, check input signals to ECU. See IDLE SPEED SYSTEM INPUT SIGNALS
table.
On Q45, fast idle is controlled by fast idle cam on non-traction control system equipped vehicles and air cut valve on traction control system equipped vehicles. Engine coolant temperature changes volume of wax element to control amount of air by-passing secondary throttle valve. As engine warms, by-pass air is reduced, reducing idle speed.
NOTE:
On Q45, see ADJUSTMENTS
article in the ENGINE PERFORMANCE Section for testing and adjustment of fast idle cam.
IDLE SPEED SYSTEM INPUT SIGNALS
| Application |
Model Usage |
| A/C Clutch Signal |
G20, M30 & Q45 |
| Airflow Meter |
Q45 |
| Battery Voltage |
G20, M30 & Q45 |
| Crank Angle Sensor |
G20, M30 & Q45 |
| Engine (Coolant) Temperature |
G20, M30 & Q45 |
| Ignition (START) Switch |
G20, M30 & Q45 |
| Neutral Switch |
G20 |
| Park/Neutral (Inhibitor) Switch |
G20,
M30 &
Q45 |
| Power Steering Pressure Switch |
G20, M30 & Q45 |
| Throttle Position Sensor |
G20, M30 & Q45 |
| Throttle (Idle) Switch |
M30 & Q45 |
| Vehicle Speed Sensor |
G20, M30 & Q45 |