P0463 is a moderately common OBDII trouble code that can occur in your Mercury Montego. It indicates that the vehicles computer has detected an inaccurate fuel level reading. It shouldn’t affect the drivability of your Montego, but it can be inconvenient.
Your Montego will get the P0463 code when the signal coming from the fuel tank indicates that there is more fuel than is mathematically possible for the fuel tank to hold.
P0463 Symptoms: Mercury Montego
This trouble code indicates that there is something wrong with the reading from the fuel tank. Most of the time, the only symptom is going to be the faulty fuel gauge, but there are exceptions. Here are the most common symptoms of P0463:
- Unreliable fuel gauge
- Gas gauge will say that the tank is full when it is not
- Fluctuating fuel levels in the tank
- Check engine light
- Out of fuel
- Low Fuel Light
Mercury Montego P0463 Code Causes
A common mistake that is made when diagnosing P0463 is replacing the fuel pump when the fuel level sensor is what needs replaced, or replacing the fuel level sensor when it’s a wiring issue.
1. Fuel Level Sensor
The fuel level sensor is one of the most common reasons that P0463 appears in your diagnostic codes.
Here’s a fantastic video on how to test the fuel level sending unit from HOWSTUFFINMYCARWORKS (YouTube).
2. Wiring
The wiring coming to and from the fuel pump can go bad over time. A shorted or damaged wiring harness can lead to a bad signal going to the fuel gauge, as well as the powertrain control module.
You’ll need to inspect the wiring harness for a short. Being that the harness is under the vehicle, and has a decent distance to the computer, it can short out or become damaged.
3. Float
Your Montego’s gas tank uses a float to measure the amount of fuel left in it. It’s buoyant, and sits on top of the fuel. As it goes down it sends a signal to the fuel gauge telling you how much fuel you have left in the tank. If something goes wrong with it, you’ll get P0463 and the check engine light.
4. Gas Tank
If the gas tank gets too corroded, or damaged, it can cause the P0463 code.
P0463 Diagnosis: Mercury Montego
The first thing that you are going to want to do is pull any other trouble codes with an OBD-II scanner. Then clear them all and see if you can duplicate the issue again by driving your Montego around. While driving around see if the fuel tank looks like it is consistently in place, or if it erratic.
Start with taking a look at the wiring harness first. You don’t want to replace a fuel level sensor or fuel gauge without making sure that the wiring harness going to/from the sensor is ok. You’re going to look for faulty wiring or a short circuit. Here’s a great article that explains how to do that: How to find a short (BackYardMechanic).
If the wiring looks good, you’ll need to test the sensor itself. The video above on this page will help you do that.
Conclusion: P0463 Montego
P0463 is challenging to diagnose, due to the location of the fuel level sensor and wiring. Good luck diagnosing your Mercury Montego. If there is anything that you would like to add, please leave a comment.