Fuel Level Sensor Voltage code

Hello, a wiring issue can cause this code, the PCM (engine computer) is seeing a low voltage reading for the fuel tank level sensor, (the code setting criteria is a voltage reading of below 0.4volts (400mv). The fuel level sensor works by having high resistance threw it when the gas tank is full and the resistance lowers as the fuel level lowers.

*What was the reason for replacing the fuel pump assembly first? And did the fuel level gauge work prior to replacing the new pump?

I will post the code flow chart to help give some direction, but if the fuel level sensor worked before replacing the pump, then either the new pump assembly is faulty, there is a wiring harness issue (ie the connector at the pump has a pin fitment issue), etc.
If you can reach the fuel pump connector easy enough, try plugging in the old fuel pump assembly, move the float level up and down and you should see it change the fuel level on the instrument cluster, if you do, then you know its not a wiring issue up near the instrument cluster, either way you will have a better idea of what the fault may be. Ill post some service info for you here in a minute. Retrace your steps.

When I plug in the old pump, the gauge doesn’t even attempt to lift or lower. I checked the wiring under the tank and it looked fine. But looks don’t always tell things. I truly hope a wire didn’t break inside the car that runs the level sensor unit. However when I reset the PCM, it works for a bit and then stops. So it’s definitely a wire issue

Here is the code setting service info, along with the oem wiring diagram for the fuel level sensor, thankfully they have a diagram which is pretty easy to read compared to some. Let us know what you find and of course if you have any further questions.

Just seeing your latest posting, we could have you disconnect the PCM connector that has the two wires for the sending unit and check for a complete circuit from the two PCM wires, I will also find this C300 connector so you can check it for corrosion, give me a minute here.

I didn’t know they was a in line connector between the PCM and Fuel Pump. Maybe I should check there when I find the location of it. PCM looks okay.

Here is the C300 connector location and pinout (drivers side lower dash, kick panel area), youre looking for the Purple wire and the Black wire at C300. If you unplug the connector, technically you should read 5volts on the Purple wire with the key On, the PCM should be supplying 5volts to the fuel level sensor.
Then to verify the circuit is not and Open, check the resistance on the same two wires with the connector still unplugged, just make sure youre checking the sensor side of the harness. So you are measuring the circuit and sensors resistance from one end to the other. You should get a reading, not an OL reading on the meter.
And you are not getting any codes setting in the instrument cluster or any other modules?

Is this the connector? I found it on the side of the lower dash

Go by the wire colors on the oem wiring diagram, you should have a Brown wire (pin A), White wire pin-B, x2 Black wires pin-C pin-E, Red wire pin-D, Gray wire pin-F, DarkGreen wire pin-G, LightGreen pin-H, Purple wire pin-J, White wire pin-K. If I have that all correct,

I cannot tell from this picture if thats the connector, but it is the right color connector, just see if those wire colors match, and check for a 5volt reference.

We have a problem. The purple wire has no power going to it even with the car on. And my test light grounded too. So I may have just found something.

We also have no five volt reference as well.

Are all the wire colors matching the wiring diagram? and is the other half of the connector there hanging from under the dash? You wont see much with a test light on a 5volt reference circuit, the reference circuits are very low current and only used for sensor readings. Next you'll need to check for 5volts right at the PCM just in case that connector under the dash is not the one we are looking for. C300 looked more like it was behind the left lower kick panel, but then again with a vehicle this old, its been taken apart and put back together over the years many times Im sure.

Yes all the wires are matching that diagram so that is the correct harness. PCM is getting power at the harness

It also says there is a c413 as well. Maybe I should check that one as well? But I don’t see the location for that one

This is the PCM C2 connector, if you can back probe the Purple wire while its still plugged into the PCM, that would help get an accurate reading, we dont want to go down the wrong path due to chasing the incorrect wire, dont ask why I know that =).
But being easy on it, and dont force it because you can short pins inside the PCM connector together by accident and get all kinds of strange readings.
And I am not sure if this is correct, but I also noticed the wiring on the ground side of the level sensor changes colors 3 times. At the sensor the Low Reference wire is Black/White, then another connector (C413 they have almost hidden), then the wire goes to Orange/Black, then apparently back through the C413 connector, where it changes over to a solid Black wire to the PCM. I will locate C413 as well

Yup good catch, I was already looking for its location.

Here is C413's location and pinout, it is a pass through connector, from the interior to the under side of the vehicle, good location to check for corrosion.

Maybe run through the flow chart real quick, it does have disconnecting C413 and testing for shorts right there.

We have no power at all going to the purple wire on the PCM. No light from the test light either. It’s the connector with the blue tint on it right?

Its listed as Lite Grey in color, that might be the rubber weather pack color also though, I go by wire color and location in the connector when I am trying to ID a certain one. The oem diagrams are going to be the closest with correct wire colors.
Do you have 5volts on any of the wires coming from that connector on the body side of the harness? Are you grounding your meter at battery negative? And this might sound dumb, but are your meter leads ok? connected together and shaking the leads you dont have any high resistance showing up on the meter. Just want to make sure we dont have any equipment failure.

I just messed up. I pinned the wrong connector and now my instrument cluster isn’t showing anymore. No lights other than the SES light.

pinned the wrong connector? check all your fuses with a test light first. Make sure you have a good ground when testing with a meter or test light.

Blown fuse. I’m now checking out the other connections on the PCM plug and the same ordeal. No power on the pin for the fuel level sender signal circuit

We indeed do have a 5 volt reference as it’s getting more than 5 volts at the black wire. Light also lights up too. Would there possibly be a short somewhere with more than 5 volts

We however don’t have any volts coming off the main purple wire running the level sender at the PCM plug

yes almost anything is possible in this field. Whats the actual voltage reading you are getting?

This A pin? Black wire ground..

Are these 8 digits in your Vin #?

Yes my vin ends in 200021

The black wire and black and white wire are reading and so is the purple one under the car as the ohms change on our voltmeter. But no power to the PCM pin

Ok I doubt this applies, but there was a technical service bulletin on in tank corrosion, but I think we are dealing with something else here.
Were you able to check the PCM connector's reference voltage without unplugging the PCM? If so, with the key off, check the condition of the PCM connectors pins themselves, and check both connector for any corrosion or broken wires right inside the PCM connectors, try to look as far into the connector as possible, green corrosion can grow right inside of wiring and you cant even see it sometimes.
Another check, with the C413 disconnected, PCM C2 disconnected, key Off, see if there is continuity to ground, being that the circuit is almost isolated.
in the 4th diagram, that other Black wire is also a ground which runs into the PCM.

Wait are you taking resistance readings or voltage readings? Because you cant properly measure resistance with a component plugged into a circuit.

Okay found a discovery. When it’s plugged into the car, it goes to open loop. Unplugged it shows 0.03 volts. Seems like we may have a break somewhere

Ok well, see what else you find, I need to go drop off a vehicle to a customer, but we will get right back on this when I return. Shouldnt take too long.