Idle Air Control Motors

The Idle Air Control Motor (IAC), also referred to as the Throttle Air Bypass Valve (TABP), is a stepper motor controlled by the vehicle’s onboard computer. The computer moves the pintle in and out of an opening that bypasses the throttle blade. This allows the computer to precisely control idle speed when varying loads are placed on the engine.

Common causes of Idle Air Control Motor failure:
• Build-up of carbon, rust, or debris
• Partial or complete jamming of the actuator

Symptoms of a failing Idle Air Control Motor may include:
• Engine surging or stalling
• Poor idle conditions
• Check Engine Light on

The following OBD II error codes are the most commonly found with this product type. On-Board Diagnostic (OBD) systems are integrated into the computers of our vehicles to monitor emissions. The first generation of OBD requirements was implemented in California in 1988. Since then, these requirements were adopted by the US EPA for all passenger vehicles manufactured after 1996. In 2005, OBD systems then also became mandatory for heavy-duty vehicles and engines up to 14,000 lbs. GVWR. In 2008 the EPA finalized OBD regulations for 2010 and later heavy-duty engines used in highway vehicles over 14,000 lbs. GVWR and made changes to the OBD requirements for heavy-duty applications up to 14,000 lbs. GVWR to align them with requirements for applications over 14,000 lbs. GVWR.

OBD II is now the standard in diagnosing vehicle emissions in. The codes listed for this product type are common instances that may relate to your vehicle and should be used as a guide only. Walker Products will not be held responsible for any use of this information. It is highly suggested that you consult with a professionally trained mechanic prior to any automotive repair, and that you follow all vehicle manufacturer and EPA guidelines for removal, replacement, diagnostics, OBD II code clearing, ECU and PCM relearn procedures.

o P0505 Idle Air Control System
o P0506 Idle Air Control System RPM Lower Than Expected
o P0507 Idle Air Control System RPM Higher Than Expected
o P0508 Idle Air Control System Circuit Low
o P0509 Idle Air Control System Circuit High
o P050A Cold Start Idle Air Control System Performance
o P050D Cold Start Rough Idle
o P0511 Idle Air Control Circuit
o P0518 Idle Air Control Circuit Intermittent
o P0519 Idle Air Control System Performance
o P2104 Throttle Actuator Control System – Forced Idle
o P2176 Throttle Actuator Control System – Idle Position not Learned
o P2177 System Too Lean Off Idle
o P2178 System Too Rich Off Idle
o P2179 System Too Lean Off Idle
o P2180 System Too Rich Off Idle
o P2187 System Too Lean at Idle
o P2188 System Too Rich at Idle
o P2189 System Too Lean at Idle
o P2190 System Too Rich at Idle
o P256A Engine Idle Speed Selector Sensor/Switch Circuit/Open
o P256B Engine Idle Speed Selector Sensor/Switch Range/Performance
o P256C Engine Idle Speed Selector Sensor/Switch Circuit Low
o P256D Engine Idle Speed Selector Sensor/Switch Circuit High
o P256E Engine Idle Speed Selector Sensor/Switch Circuit