P1551

P1551
Idle Air Control (IAC) Valve - Interruption.

P1552
Idle Air Control (IAC) Valve Closing Coil - Below Lower Limit.

P1553
Idle Air Control (IAC) Valve Closing Coil - Upper Limit Exceeded.

Function:
Idle speed control is realized via the idle air control valve. Two coils, the opening coil and closing coil, are integrated in the idle air control valve for this purpose.
In the basic or emergency position, neither of the coils is triggered. To increase the rpm, the opening coil is triggered with a certain pulse duty ratio; the closing coil is triggered to control the rpm.

Diagnostic Conditions:
A fault is recognized and stored in memory when the engine speed is higher than 80 rpm and the battery voltage is between 7.5 Volt and 17 Volt.

NOTE: If a fault occurs that would lead to very high engine speed, a late adjustment of the ignition angle sets in to act as an engine speed limiter.

Wiring Diagram:




Diagnostic Procedure:

DTC P1551:

DTC P1552:

DTC P1553:

1. Check coil resistance of IAC Valve.
1. Remove connector for IAC Valve.
2. Connect ohmmeter to pins 2 and 1 at IAC Valve.

Specified Value: 14 - 17 Ohms at 20°C.

2. Check wiring from ECM to IAC Valve for continuity.
1. Remove connector for IAC Valve.
2. Connect special tool 9616 to wiring harness.
3. Connect ohmmeter to special tool 9616, pin 2 and to IAC Valve connector, pin 1.

Specified Value: 0 - 5 Ohms.

If meter reads 0 - 5 Ohms, check wiring for chafing and pinching damage.

3. Check wiring from ECM to IAC Valve for short circuit to ground.
1. Remove connector for IAC Valve
2. Connect special tool 9616 to wiring harness.
3. Connect ohmmeter to special tool 9616, pin 2 and to ground.

Specified Value: Infinite Ohms.

If meter reads 0 - 5 Ohms, check wiring for chafing and pinching damage.

4. Check wiring from ECM to IAC Valve for short circuit to B+.
1. Remove connector for IAC Valve.
2. Connect special tool 9616 to wiring harness.
3. Connect voltmeter to special tool 9616 pin 2 and to ground.

Specified Value: 0 Volt.

If meter reads battery voltage, check wiring for chafing and pinching damage.