P050A: Cold Start Idle Air Control System Performance

What Does The P050A Code Mean?

A stored code P050A means that the powertrain control module (PCM) has detected a problem with the idle air control (IAC) system. The term cold start refers to an engine drivability strategy that is implemented only when the engine is at (or below) ambient temperature.

Controlled by the PCM, the IAC valve is responsible for regulating air flow through the throttle body and into the engine intake manifold when the engine is at idle.

With the throttle plate closed, very little air is allowed to enter the engine through the throttle bore. The engine will not idle smoothly with this miniscule amount of air. A steady supply of vacuum would be ineffective at promoting a smooth idle because variations in atmospheric pressure and engine temperature require varying degrees of intake air. An automatically adjustable method for varying idle air is required. The IAC valve meets this requirement.

The IAC is an electronically controlled valve that is mounted on the throttle body. It consists of a single housing with an electric motor and a pair of small air chambers. The two open chambers have a cone-shaped valve and seat between them. The IAC is mounted near the throttle bore so that one chamber is aligned with an intake opening outside the throttle plate. This chamber is called the inlet chamber.

The second chamber (outlet chamber) is positioned so that it is aligned with an intake opening inside the throttle plate. When the valve is pushed flush into the seat, no air may pass between the two chambers. As the valve is lifted off the seat by the electric motor, ambient air can be drawn through the inlet and outlet chambers and into the intake manifold.

The PCM uses input data from the crankshaft position sensor and camshaft position sensor to calculate engine RPM. Engine idle speed is programmed for a specific RPM level and the PCM uses the IAC motor to realize it. If actual engine RPM is higher than desired RPM, a voltage signal is output from the PCM to the IAC motor.

The motor extends the valve into the seat and air flow to the engine is restricted; RPM level decreases accordingly. By the same token, if actual engine RPM is lower than desired RPM, the PCM emits the opposite voltage signal. The motor retracts the valve from the seat and more air is allowed to enter the intake; the RPM level is increased. Since desired RPM level is precisely and aggressively targeted by the PCM, the valve is moved in very small increments, continuously.

If the PCM cannot effectively control the engine RPM level at cold start, a code P050A will be stored and a malfunction indicator lamp (MIL) may be illuminated. Multiple failures will likely be required for MIL illumination.

What Are The Symptoms Of The P050A Code?

Symptoms of a P050A engine code may include:

• High or low engine RPM level
• Engine may stall at idle
• The accelerator pedal may have to be depressed for the engine to start
• Unusual tapping or popping noise from IAC motor

What Are The Potential Causes Of The P050A Code?

Causes for this code may include:

• Defective or dirty IAC valve
• Vacuum leak
• Open or shorted circuits or connectors
• Defective electronic coolant temperature (ECT) sensor

How Serious Is This P050A Code?

A code P050A should be treated as severe because engine drivability may suffer from the conditions which cause it to be stored.

How Can You Fix The P050A Code?

If ECT related codes are stored, diagnose and repair these before attempting to diagnose the P050A.

Certain vehicle applications will exhibit an audible tap or pop when conditions are right for this code to be stored. If you are working on a Ford motor company product with a stored code P050A, and this noise is heard, suspect that the IAC is defective.

A source of reliable vehicle information, a diagnostic scanner, and a digital volt/ohmmeter (DVOM) will all be needed to diagnose a code P050A.

Component testing procedures and specifications, wiring diagrams, connector face views, connector pin-out charts, and diagnostic flow charts can be found in your source of vehicle information. These things will be required for a successful diagnosis.

A visual inspection of the IAC valve and all related wiring and connectors may yield a quick diagnosis. Look for varmint damage on the wiring harness atop the engine.

If the IAC valve and seat are carbon fouled, the valve will not seat properly. The valve may be cleaned on some vehicles but follow manufacturer’s recommendations carefully.

Use the DVOM (ohms) to test the IAC motor. Disconnect the motor from the harness and use the test leads to measure resistance. If the IAC motor does not comply with specifications, it is bad.

If the IAC motor is within specs, reconnect the IAC motor connector. Probe the input voltage circuit and ground of the IAC connector using the test leads of the DVOM. If voltage is within specifications and a ground is present, suspect that the IAC valve/motor is faulty.

Note: Search applicable technical service bulletins (TSB). If you find a TSB that matches the vehicle type, codes, and symptoms that you are experiencing, it will help you in your diagnosis.

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> IAC Valve
>>> ECT Sensor
>>> Autel Scanner MaxiCOM MK808S
>>> KAIWEETS Digital Multimeter

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Check This Video For Reference

Reference Sources

Diagnostic Trouble Code (DTC) Charts and Descriptions for P050A – Page 82.