Codes P018D, P0300, P0446 and P0463

Tiny
7ELEVEN
  • MEMBER
  • 2015 GMC ACADIA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 133,333 MILES
Sorry, this is so long. We are desperate for ideas. These are the events that have taken place.

The gas gauge stopped working a few months ago. We didn’t have the money at the time and found a work around by monitoring mileage.

A month and a half after the gauge stopped working, the battery drained and was replaced. Plugged in a new battery and gas gauge started working briefly. Then dropped to E and didn’t move.

About 2 months later sitting at a light the idle got a little rough and gradually increased but never stalled. Right before I would expect it to stall the Traction Control switched off and the idle smoothed out. I was able to drive it home, but it would hesitate and when pushing the gas at nothing would happen. Then it would accelerate as normal.

The rough idle is not consistent, it can happen shortly after the car is started or 15 minutes after it’s been running. The vehicle is drivable. (We are not driving it in fear of making the issue worse)

These are the codes we got:

P018D
P0300
P0446
P0463

Actions taken:

Changed out fuel pump in tank module-same issue persists.

Changed out gas cap-same issue persists.

Changed out ignition coils and spark plugs- same issue persists.

Took out fuel injectors, cleaned and replaced- same issue persists.

Replace fuses for the ECM/FPM IGN and FPM- gas gauge worked briefly then stopped same issue persists.

We need ideas of what we could be missing.
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Friday, April 22nd, 2022 AT 12:22 PM

5 Replies

Tiny
AL514
  • MECHANIC
  • 3,979 POSTS
Hello, these are circuit codes, not necessarily a fuel pressure issue, both these two codes P018D and P0463 are for Fuel Pressure sensor "circuit" high and Fuel level sensor "circuit" high input. The Fuel pressure sensor is on the fuel line in this vehicle and the fuel level sensor as you know is in the fuel tank. But these three components share a Ground connection. The Fuel level sensor (1st Diagram), the Fuel Pressure sensor, and the Fuel Tank Pressure sensor all share a Ground together. The Fuel Tank pressure sensor will set an Evap code because it's part of that system.
The Ground is circled in green in both diagrams. With a bad Ground wire, it will set voltage high codes because the voltage for the sensor is not being pulled to Ground and the voltage signal stays high. The Ground wire is the one thing that can cause all three of those codes at once. The P0300 is a random misfire code that is the result of the other conditions. You need to track down this Ground wire in the diagrams and find out where it is either broken or has a bad connection.
It's the tan colored wire on all the components, including on top of the fuel tank. These sensors work on a 5-volt Reference circuit, but this explains all the codes together.
The other two diagrams are the first two connectors coming from those sensors, you'll see them on the wiring diagrams. The X305 is a connection in the fuel tank so I would check the wiring first. Since you have already been in the fuel tank.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-a-car-electrical-system-works
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Friday, April 22nd, 2022 AT 1:39 PM
Tiny
7ELEVEN
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  • 3 POSTS
Perfect! Thank you, we are taking the tank back down and working on this today. I really appreciate your help and will update with findings!
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Sunday, April 24th, 2022 AT 7:52 AM
Tiny
AL514
  • MECHANIC
  • 3,979 POSTS
That x100 connection is not on top of the fuel tank though, it is in the engine compartment near a fuse panel. The connector is only listing the Fuel Tank Pressure Sensor Low Reference, but you can see by the last diagram that all 3 low ref (Grounds) run through that connector.
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Sunday, April 24th, 2022 AT 2:06 PM
Tiny
7ELEVEN
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AL W, please accept my apologies for the delayed response! The family has been under the weather, and I haven’t been able to get back to you! The Tan wire in the tank harness was damaged from what looked like debris hitting it. We striped it and spliced it and it totally fixed that problem! You are a life saver! My family and I cannot thank you enough!
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Sunday, June 5th, 2022 AT 1:49 PM
Tiny
AL514
  • MECHANIC
  • 3,979 POSTS
That's great news, this was awhile back. I hope the family is doing better. Yeah, the tan ground wire was the only thing that tied all 3 components together. Glad it was something simple. It was either that or possibly a failed module.
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Monday, June 6th, 2022 AT 12:37 PM

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