P0463, Check Engine Light On, Fuel Gauge Reads Half Full

My check engine light is on (but very dim) and it’s throwing code P0463: fuel level sensor A circuit high input. I’m using a code scanner that lets me delete codes.

I replaced the sending unit in the tank, and it’s still throwing the code. I unplugged the pump/sending unit, and it’s still throwing the code. I unplugged the instrument cluster, and it’s still throwing the code. The fuel gauge reads half full by the way, so it looks to me like it’s getting a proper signal. Any idea what might be causing this? Could it be a bad ECU?

It’s a 1996 4.0 manual btw

What research or diagnostics makes you suspect the ECU ? Always start any diagnostics with the basic inspection and testing, wires, fuses, wire plugs, circuits, sensors and components, and grounds. Shotgunning random new part at an undiagnosed problem seldom works.


P0463 JEEP

Possible Causes

- Faulty fuel level sensor
- Fuel level sensor harness is open or shorted
- Fuel level sensor circuit poor electrical connection

Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

The harness looks fine. I replaced the sending unit because everything I read indicated that was most likely the problem (and the fuel pump had gone bad from sitting). I tried something just now though: I hooked up the old sending unit outside the tank and cleared the code. It worked! I was under the impression the gas in the tank wasn’t terribly old, but the guy I bought this from was definitely shady. I’m thinking the gas is so bad that it’s affecting the resistance in the sensor. I also just noticed that the O2s/HTR/CAT symbols are flashing on my code reader but aren’t throwing any codes, not sure if it’s from not being driven or just really old gas. I’m going to drain the tank today and refill it to see what happens.

It means they are in reset mode and are not ready for a emissions test.