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Truck Wont Start Code P018C on Your Ram 1500 4th Gen 2009-18

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Created on: 2021-01-04

Andy shows you how to diagnose a hard to start engine with code P018c. This video features a Ram 1500, but this problem is also common on GM trucks, and could occur on any vehicle that monitors fuel pressure!

In this video, we're going over the fuel rail pressure sensor circuit on this fourth-generation RAM.

We have this fourth-generation RAM 1500. There's no drivability issues. We happen to have a check engine light with a code P018C, which the description is fuel pressure sensor circuit low. What that code is referring to is the pressure sensor right here. It's on the driver side at the top of the engine, where the fuel line comes into the fuel rail.

The reason why you have this code is the PCM or the computer, basically the brain of the vehicle, is trying to get a signal from that sensor, and it's getting a very low voltage signal, which it's inaccurate, so it thinks there's either something wrong with the fuel pressure or the sensor itself.

What we want to do is see what the computer is actually seeing from that sensor. So, we're going to use the scan tool. We're going to click on variable speed, fuel pump actual rail pressure, and then also the desired rail pressure. So, this is what the computer wants it to be, and this what it actually is. We'll confirm. And those are the two readings. So, that looks pretty accurate right now. Now, that's just with the vehicle sitting still, not running. Now, if you don't have the scan tool, what you can do is look at the connector, and make sure the connector is on there, and just take a look at the wires and see if the wires look good. Everything looks good here, so go on to the next step.

Now, these are the readings with the vehicle running. Now, the desired pressure should be 58, and it's still stuck at 62.3. So, that's pretty much saying that the sensor is not moving and it should be. It should have dropped down. So, this 62.35 is a default. Right now the sensor is disconnected. If I plug the sensor in, it goes to zero. If we wait a minute, it goes back to that 62.35. If I disconnect it, it goes to 101.5, and then it goes back to the default. And this is what it should look like with a working fuel pressure sensor.

So, we started out with this code, the P018C, which is fuel pressure circuit low. Now, in the diagnostic flow chart, what you need to do is disconnect the connector, and turn the key on. And if you end up with this code, the circuit high, which is pretty much the opposite, then what the problem is is actually the sensor itself. That basically tells you that the wiring to the sensor is working properly in the connector and that all you have to do is replace the sensor.

If you didn't have a fancy scan tool like this that you could actually view the data of the fuel pressure sensor, when you disconnected the sensor and you got that code, that's another way you know that that sensor is bad. If you disconnected that sensor, and you didn't get that other code, most likely you have a short somewhere where the wire is contacting something metal on the car. So, when you get that fuel pressure sensor code, you either have a bad fuel pressure sensor, bad wiring, a connector, or there might be a problem in the computer, the PCM. More often than not, it's just a fuel pressure sensor. I hope you enjoyed this video. If you did, make sure to subscribe to our channel, ring that bell, turn on all notifications so you don't miss any of our videos.

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