P1504 - FAULT CODE - OBD2

P1504 Code failures by brands

P1504 FORD, LINCOLN, MERCURY: INTAKE AIR CONTROL CIRCUIT MALFUNCTION

Description of DTC code P1504

The IAC (Inactive Air Control) valve is usually located on the throttle body. This valve regulates the engine's idle speed, preventing the engine from stalling. For this purpose, it controls the air around the throttle plate that enters the engine.

The PCM (Powertrain Control Module), as the engine management module, controls the IAC valve by sending voltage pulses to it. By doing this, the valve's internal motor can move and direct the flow of air found in the throttle plate. The Power Control Module regulates the wanted idle speed or bypass air and marks it in conjunction with the IAC valve, using a specified duty cycle. Consequently, the valve controls the bypass air. The Engine revolutions per minute are also monitored by the PCM. These can decrease or increase the valve duty cycle to get the desired RPM.

When the diagnostic code P1504 OBDII is set, it means the PCM has found a malfunction of the circuit that controls the intake air, being closely related to the IAC valve.

Symptoms of fault code P1504

Check Engine light ON.
During idle speed, the vehicle exhibits performance instabilities.
In cold weather conditions, starting the engine is difficult.

Causes of OBD2 P1504

Reasons to store the DTC P1504 OBD2 DTC code :

Inactive Air Control valve wiring may have common damage.
The IAC valve circuit may be shorted or open.
The IAC valve may be in bad condition.

Possible solutions of the DTC code P1504

To solve the P1504 OBDII fault code, try this:

Consult the Technical Service Bulletins.
Check for common burn damage, corrosion, or wear on wiring or other electrical components. Repair any such conditions that are present.
Measure the voltages of the control circuit of the Inactive Air Control Valve, and check if they match the manufacturer's specifications. If you find inconsistencies, make the right repairs.
Inspect the IAC valve gasket, it may be leaking or damaged due to the air pressure to which it is exposed. If cleaning does not fix the situation, there may be defects on the valve, replace it.