Idle Air Control Valve (IAVC) - From 99MY

The idle air control valve is positioned at the top rear of the engine, on the side of the air inlet pipe. The unit is clamped to the inlet manifold by two bolts passing through 'P' clips.

A grey three-pin connector is provided at the back of the unit. One wire supplies the voltage feed from the engine compartment fusebox, while the other two wires carry the valve positioning control signals.
The IACV is used to make adjustments to optimize the engine idle speed under all operating conditions. Engine load at idle will vary in reaction to a combination of conditions and influences such as engine friction, water pump , air conditioning, altitude etc. The IACV utilizes closed loop control to compensate for the changing conditions by regulating the air flow into the engine.

The IACV utilizes two electromagnetic coils which use opposing PWM signals to control the positioning of a rotary valve. The rotary valve position determines how much air is allowed to flow through the bypass route.


CAUTION: Do not try to forcibly set the valve position, the actuator cannot be serviced. In the event of failure the IACV must be replaced as a unit.


If one of the electrical circuits supplying the PWM signals tails, the ECM switches off the other circuit to prevent the valve from biasing towards a maximum or minimum setting. Under these conditions, a default position for the valve is provided by a permanent magnet, which sets the valve position to maintain the idle speed at a fixed value of approximately 1200 rpm with no load applied.

During cold start conditions, the idle speed is held at 1200 rpm in neutral for 20 seconds. Ignition timing is retarded as a catalyst heating strategy.

If the IACV should fail, the following symptoms may be observed:
- Either low or high idle speed
- Engine stalls
- Difficult starting
- Raised idle speed in default condition.

An IACV failure is likely to occur for the following reasons:
- Rotary valve seized
- Faulty actuator
- Connector or harness fault
- Intake system air leak
- Actuator port or hoses blocked, restricted or crimped

If the IACV should fail, the following fault codes will be generated by the ECM diagnostics, which can be retrieved by Testbook:

- P0101 - Blocked IACV valve - rpm error high
- P0101 - Blocked IACV valve - rpm error low
- P1509 - Short circuit to battery supply - opening winding
- P1509 - Short circuit to ground - opening winding
- P1509 - Open circuit - opening winding
- P1550 - Short circuit to battery supply - closing windings
- P1550 - Short circuit to ground - closing winding
- P1550 - Open circuit - closing winding