Code P018C and Your Fuel Pressure Sensor
Have you noticed your engine is hard to start, or won’t start at all? Your check engine light is on, with the code P018C? That relates to the fuel pressure sensor and the issue could be low fuel pressure. Check out this video where Andy shows you how to diagnose a hard-to-start engine with code P018C.
What Is Code P018C?
P018C is an OBD II fault code that stands for “Fuel pressure sensor “B” Circuit Low”. There are a few things that can cause this code like a bad sensor, or high or low fuel pressure. It pops up when the Power Control Module (PCM) receives an erratic signal voltage from the fuel pressure sensor. The problem is common in vehicles that come with a sensor to monitor fuel pressure. You’ll mostly get a check engine light but no drivability issue.
During normal driving, pressure varies constantly within the fuel rail. This is due to changes in fuel demand as you drive in different conditions. The fuel pressure sensor converts the pressure changes into a signal voltage that goes directly to the PCM. The light should only come on when the high or low fuel pressure is outside of the normal range.
The PCM then makes adjustments to the pulse width of the fuel injectors. This either increases or decreases the amount of fuel being sent to the engine, hence, maintaining a constant fuel rate and pressure within the fuel rail.
As you go on with your daily driving, the PCM expects to receive an accurate signal voltage from the fuel pressure sensor that reflects changes in pressure within the fuel rail. When the PCM notices that the signal voltage is low and does not reflect what it expects to receive, it will activate the check engine light and set the code P018C.
Symptoms of Code P018C and High or Low Fuel Pressure
As mentioned earlier, the two most common symptoms of this problem are a check engine light and a stored OBD-II trouble code. However, there are several other signs that you may notice depending on the application. They include:
- A hard start or a no-start condition
- Engine shuts off immediately after starting due to a deactivated fuel pump
- Rough idles, stumbling or hesitation when you try to accelerate
- Unpredictable and frequent stalls
- Periodic oxygen sensor related codes
Common Causes of P018C Code
- Faulty fuel pressure sensor
- Burnt, shorted, corroded, damaged, or disconnected wiring
- Faulty or corroded connector
- A faulty Power Control Module (PCM)
- Poor installation of aftermarket parts and accessories
How to Diagnose and Repair P018C Code
The first step to diagnosing a P018C code in your car is to check the wiring that goes to the fuel pressure sensor. You want to see if there are any damaged wires or loose connections. There could be a short somewhere where the wiring is in contact with a metal component of your car.
If everything looks good, the next step is to check the actual fuel pressure versus the desired fuel pressure reading. Start by connecting a scan tool to the car’s computer and click on the FPS data parameter. Both the desired and actual pressure readings should be at default when the engine is off.
Generally, the fuel pressure sensor is designed to send a high voltage signal when fuel pressure increases inside the fuel rail and a low signal voltage signal when it drops. Delayed or inaccurate signals from the sensor will affect how fuel is delivered through the injectors.
To make this reading easy, manufacturers use code settings based on time (in seconds) when changes that do not reflect expected fuel pressure values (in units of pressure) are reflected by the fuel pressure sensor as the fuel pump sends pressurized fuel either at its minimum or maximum voltage limits. To check this, start your engine and check the readings on the scan tool.
If the difference is more than a couple of psi, the fuel pressure sensor is bad and needs to be replaced. A bad fuel pressure sensor will mostly not move away from the default reading. You can go further and pull it in and out and observe the changes in the FPS data parameter. Make sure to first release the pressure within the fuel system before doing this. Fuel can spray all over the engine, creating a potential risk of having a fire.
If you discover that the actual and desired fuel pressure readings are both below the manufacturer’s recommended fuel pressure specifications, the fuel pressure sensor may not be the culprit. Chances are, you have a fuel delivery problem. It could be due to a bad fuel pump or something else within the fuel system. You’ll need to check it out and do the necessary repair.
Another way to check for a faulty fuel pressure sensor is to disconnect the connector and turn the key on. You should find your pressure sensor and the corresponding wiring connected directly to the fuel rail. If you end up with the code P018D instead of P018C, you have a bad fuel pressure sensor. If you didn’t get the code, you most likely have a short somewhere. There could be a wire that’s grounding to a metal part of the vehicle.