Lotus 2004 ELISE Service Notes page 158

Lotus Service Notes
Idle Speed Control
P0506 Idle Air Control System RPM Lower Than Expected
P0507 Idle Air Control System RPM Higher Than Expected
P0508 Idle Air Control System Circuit Low (prior '06 M.Y.)
P0509 Idle Air Control System Circuit High (prior '06 M.Y.)
Description
Prior to '06 M.Y. the ECU controls the air entering the engine with an idle air control (IAC) valve. To increase the
idle the ECU commands the IAC to open up. This allows more air to bypass the throttle blades. To decrease
the idle speed the ECU commands the IAC to close up. This will reduce the amount of air bypassing the throttle
body. The ECU performs low and high circuit checks when it is activating the component.
For '06 M.Y. onwards, the electronically controlled throttle needs no IAC, as the ECU commands the throttle
valve itself to control idle speed.
Component connections (prior to '06 M.Y.)
Connector Description
1 Idle air control value
2 Battery Voltage
3 Ground
Malfunction Criteria
P0506 – This code is set if the engine fails to achieve the desired idle speed by more than 100 rpm.
P0507 – This code is set if the engine fails to achieve the desired idle speed by more than 200 rpm.
P0508 – This is set when the ECU does not get the expected feedback (prior to '06 M.Y.).
P0509 – This is set when the ECU does not get the expected feedback (prior to '06 M.Y.).
Enable Criteria:
• Engine at idle speed
• Battery Voltage between 10 – 16 V
• Idle speed learn limit ± 15%
• Timer expired 5 seconds
Monitor: Continuous
Potential failure modes:
• Throttle body sticking (not fully closing) (prior to '06 M.Y.)
• Connector / wiring corroded or loose connections (prior to '06 M.Y.)
• Throttle linkage / cable binding (prior to '06 M.Y.)
• Induction system air leak
• Excessive engine load from front end accessory drive system, e.g. water pump seizing
Notes:
The MIL will be illuminated if the fault is present for 2 consecutive trips.
sn_emp_cyclone.indd 35
P0506
P0507
P0508
P0509
ECU Pin ECU Connector
35 52 Way
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Section EMP
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