The easiest way to diagnose a problem with your Ford is by reading the code relayed by the Power Control Module (PCM). The code could indicate a severe or minor issue with the car. Hence, you should always find out what it means. Getting such a code can be troubling if you are a new car owner, especially when you are far away from a mechanic shop. Code P1504 is one of those codes that can appear in your Ford vehicle, especially when idling. But what does this code mean? How can you fix it? Don’t worry! Today, we will discuss everything you need to know about code P1504.
What does code P1504 mean?
The Idle Air Control (IAC) Valve regulates the air needed to maintain an idle speed. This valve relies on information it receives from the PCM. A problem with the valve will result in the entry of excess air. The PCM will detect this, and code P1504 will be produced. Since the IAC valve is not used at any speed when idling, you will mostly notice the fault when starting the car or during traffic.
Symptoms of code P1504
You will likely observe several symptoms when your Ford vehicle has code P1504. They include:
1. Illuminated Check Engine Light
As mentioned above, the IAC valve regulates the air that enters the engine’s cylinder during idling. Therefore, when it malfunctions, the engine will not operate normally. The PCM detects this, and the check engine light is turned on.
2. Rough Idling
If excess air flows through the IAC valve, the air-mixture ratio will not be balanced. As such, your Ford will idle roughly. Some of the symptoms you will observe are lots of vibration, inconsistent RPM, slipping sound, and idling above the regular speed.
3. Poor engine performance
An issue with the IAC valve will result in poor engine performance, especially when you are used to idling a lot. For instance, you will notice that your Ford vehicle consumes more fuel than usual. This is because excess air in the engine cylinder will make the PCM let in more fuel.
4. Hard Start
When starting the car, the throttle closes while the IAC valve opens to let in the correct amount of air needed for combustion. A faulty IAC valve will let in either too much air or too little air, resulting in a hard start. Therefore, if you find it challenging to start your Ford vehicle, code P1504 is likely to be present.
5. Engine backfires
As indicated above, a bad IAC valve will supply too little air in the combustion chamber, affecting the air-fuel mixture ratio. This will, in turn, result in some fuel being left unburned. This fuel could flow to other areas of the engine and could create a backfire.
What causes code P1504?
If you are wondering what causes this code, look no more! Below are the things you should pay attention to whenever you get code P1504. These things are related to the IAC valve; hence you shouldn’t go far when you get the code.
1. Leaking IAC
There are several airports in the IAC. These Airports are sealed with gaskets. If the gaskets start leaking, the air that reaches the combustion chamber will be less. This will result in code P1504 being produced. Things that could make the gaskets leak include excess vibration and heat. Also, the mechanic shop attendant may have adjusted it wrongly during maintenance.
2. Dirty IAC
Since the IAC valve draws in air, it is prone to dust and debris contamination. These contaminants could make the valve thin, hence limiting the amount of air reaching the combustion chamber. The valve sensors will detect this and informs the PCM. In turn, the PCM will relay code P1504 through the OBD II system.
3. Bad IAC circuit
The PCM electronically controls the IAC valve. As such, the IAC has an electric bypass circuit. If the circuit develops an electric short, the IAC valve won’t function. The IAC circuit needs around 12 volts. Any deviation from this will result in code P1504 being shown.
4. Defective IAC harness
Four internal wires link the IAC to the PCM. These wires are pulsed by varying voltages from the PCM. If one of the wires gets defective, the IAC motor will not operate well. The PCM will detect this, and code P1504 will be relayed.
5. Faulty IAC sensor
The PCM relies on the information conveyed by the IAC sensor. If the IAC sensor gets faulty, no information will reach the PCM. For instance, the IAC sensor can tell the PCM that the IAC valve has an issue, yet that is not true. The PCM will, in turn, cause code P1504 to be shown in the OBD II system. This IAC sensor can get bad due to exposure to water, debris, and even excess vibration.
6. Malfunctioned PCM
Your Ford’s PCM is basically a computer; hence it is prone to bugs. If the PCM develops bugs, it will give wrong readings. For instance, it can tell the OBD II system that the IAC valve is faulty yet good. This is usually a less severe issue; hence it shouldn’t drive you crazy. However, it can also get damaged in many ways. For example, electric shorts can damage its electric connections. In this case, you should have it fixed as soon as possible.
Can you drive with code P1504?
Since the IAC valve is only needed when idling, you can drive with code P1504 present. However, this is not recommended since it can make the engine stall. Therefore, you should try fixing it before it affects the engine. Some of the fixes you can apply are;
1. Replace the gaskets
You will hear some sound coming from the IAC valve when it leaks. When that is the case, replacing the gaskets will fix code P1504. While installing the new gaskets, remember to apply extreme caution as the gasket is fragile. If you don’t have the technical skills to perform this task, consider taking your Ford vehicle to a mechanic shop.
2. Clean the IAC
If the gaskets are fine, try checking the IAC valve for contaminants. However, you must unscrew it from the throttle body and then detach its wires. Once you have done that, pour gasoline into the IAC valve and pass compressed air through it. That will remove code P1504 from your Ford vehicle.
3. Fix the IAC circuit
Using a digital multimeter, you can check whether the IAC circuit is okay. If the multimeter gives a reading of fewer than 10.5 volts or no reading at all, you have a faulty IAC circuit. Remember that different IAC circuits need different voltages; hence you should consult your Ford manual for the correct specification. Unfortunately, it is hard to repair a bad circuit in the IAC; therefore, you should consider replacing the IAC motor with a new one.
4. Replace the IAC harness
If you spot any damage to the IAC harness, replacing it is the most efficient option. Sometimes, the harness is shorted; hence you have to check for its resistance using a digital multimeter. To do so, set the multimeter to measure electrical resistance and choose more than 10,000 ohms. If the digital multimeter gives a value less than that, the IAC harness is defective. Like the IAC circuit, replacing the IAC harness is a better option.
5. Replace the IAC sensor
The multimeter can also tell you if the IAC sensor is bad. Just connect the two wires of the IAC sensor to the multimeter. If the multimeter shows no voltage reading, the IAC sensor is faulty and needs to be replaced.
6. Reboot the PCM
If all the above fixes cannot eliminate code P1504, consider rebooting the PCM. An issue with the PCM normally goes away after rebooting it. Your Ford manual contains the procedure for rebooting the PCM. However, if code P1504 is still there after rebooting the PCM, you may have to examine the PCM for damages, such as electric shorts. The process is tedious and needs a good grasp of how to do car repairs; hence you should consider consulting a specialist.
To sum up,
You will mostly receive code P1504 when idling. This code means that the IAC valve has encountered a problem making it unable to maintain an idle speed. It is usually accompanied by symptoms such as engine backfires, poor engine performance, illuminated check engine light, hard start, and rough idling. Whenever you get this code, you should examine if the IAC is leaking or if the IAC circuit is shorted. Other cause of this code includes defective IAC harness, malfunctioned PCM, and faulty IAC sensor. By repairing or replacing these parts, you will get rid of code P1504. If you don’t have the technical know-how to fix it, you should take it to a mechanic expert to avoid damaging other parts.