Engine/Transmission (1998.5 - 2002) Fuel gauge does not read????

[Tcolesanti]

O. k. here is the short of it. My level gauge stopped working last thursday and I ripped it apart tonight. I dropped the fuel tank figuring it was a bad connection, or the float had come off. I pulled the tank, everything was good to go. I did an ohms test on the sending unit, checked out fine. Then after fighting the fuel tank back in the truck, I figured it was the fuel gauge itself. Luckily my roomate has an '02 so I swapped him dashes, still nothing. I am at a loss, I checked and there is 12v at the plug to the seding unit, I need help.

 

[FourBarR]

almost bet its the sender. i have replaced 3 since new, now have 340000 km. if you go on the search function type in fuel sender . be prepared for lots of reading.

 

[Tcolesanti]

I did an ohms test on the sender and it is within spec.

 

[tractorface]

Check harness

I do not have my manual with me but I can give you a general idea of what to check next. The computer is looking for 220 ohms empty and 20 ohms at full. Sounds to me like you have an open circuit which would make the gauge read empty all the time. The four wire connector at the sender runs along the frame to a larger connector just inside the drivers front wheel well. there will be two connectors there if I had my manual I could help you better. If it was me I would simple start at the sender and short the two wires that attach to the sender, The gauge should go to full because the resistance will be very low. Move forward one connector at a time until you find the connector with the high resistance connection ( or open connection). I'll bett a little dielectric grease well placed in he connectors will solve your problem. One note of caution is to be sure you have a manual and short the correct wires otherwise the ecm may be very . On my 99 of the four wire at the sender one is the gauge ground the other one used by the diesel is the sender wire. Ther is also a power ground and power feed used by the gassers fuel pump. On my 99 the red power wire runs up to the connector in the w\heel well and stops. It is not connectd to power. I know all this beacause I installed a capacitance type fuel sender in my truck and had to do a little re-wiring.

Good luck



For whatever reason there is not a direct connection from the sender to the gauge. The sender and gauge are both connected to the ecm so I guess there remains the remote possibility that your problem is in the ECM. I would check the wiring first

 

[Tcolesanti]

Tractorface, I Checked the plug in the wheelwell and I have 12 volt power at one lead and nothing at the other. The sending unit does nothing but increase ir reduce resistance to give a reading, right? Which wire do I ground out on the plug? Both? Hook them together?

 

[tractorface]

Trying to follow you

Not sure you have the correct wire in the wheel well or not. At the sender you can touch the two sender wires together which if everything else was working would give you a full reading. It may take a couple of seconds as for some reason the ECM seems to buffer the response time. maybe to avoid erratic readings when the fuel is sloshing. don't short anything with positive voltage on it! The ecm is acting just like your multi meter that you checked resistance with. If you touch the multi-tester leads together your meter will read 0 ohms of resistance which would be a ful tank as anything under say 30 ohms will make the gauge read zero gallons. Please be sure you have the sender wires so as not to destroy anything.

Wish I had my manual with me. Hey just thought of something. You may be able to access the drawings online at the Cummins site.

 

[Tcolesanti]

O. k. , I have two new codes set. P-0462 and P-0463, fuel sender voltage two high and blah, bblah too low. I did hook the two wires at the sending unit together the only two wires you can on my 2000. The gauge still read nothing. I will check the other plugs as soon as I can scrape the undercoating off of it.

 

[tractorface]

interesting

Hmm never got that before, like I said the damn ECM is in between the sender and the gauge. Still sounds like wiring to me. I found a drawing from my 99. Sender plug, the two wires you are concerned with do not go to C129 which is the plug I described under the wheel well, they go to C128 and I cannot think of where that one is. It may be in the same spot as I remember two plugs are there. . My bad memory sorry. Unfortunately I do not have the whole drawing and cannot trace out until I get home with the manual. the sender wire is Dark blue and white while the sensor ground is black and light blue according to the partial page I have in front of me. Sorry for the confusion on the plug location, wish I had my manual with me. One other thought creeped into my head. The senders often loose tension and the contacts pull apart. It is possible that when you tested it you held it in such a way that the contacts were touching and when it is installed they are not. I know one of my senders was like that.

I can send you the drawings tomorrow, not even sure if 99 and 2000 are the same. Anyone help out on this point???

 

[Tcolesanti]

Yeah, the sending unit wires don't clip on like my father's '95 they are soldered on the sending unit itself and its just a plug on the bottom of the plastic module. I tested the sender at the external plug of the module where it connects to the chassis wiring. I got 20 and 220 for ohm readings. I will try to trace the wires better today if I have time but I need this gauge to work soon.

 

[tractorface]

Ok

Looks like C128 IS one of the two connectors above the cab mount in the drivers wheel well. The Dark Blue/White wire goes from the sender to C128 to connector C130 which is at the Power distribution center (fuse box where most folks mount the EZ), from there it goes to the far left plug on the PCM (mounted behind the Air cleaner on the passengers firewall). The other wire is the sensor ground. This is a black/light blue wire which leaves the sender connector and goes to a splice block in the Power distribution center. It is spliced to the sensor grounds for the battery temperature sensor and the vehicle speed control horn switch (are they all working?) from there it makes its way to C130 (above cab mount) and finally enters the PCM on the far right plug. If you have an automatic it is spliced to the transmission solenoid assembly. Hope this helps you trace the wiring. (assuming 99 and 2000 are similar)

 

[Tcolesanti]

I am really at a loss. I checked the plug at the wheel well and did an ohms test there. I got 158 ohms. It had like 10 gallons in it. I found out how to do a self diagnostics check on the dash itself and it checked out fine. I looked at the PCM but I would have to have some better weather to get into checking it. If the Sending Unit in the tank checks out on an ohms test is there still a possibility it could be bad??

 

[tractorface]

I don't see how

The PCM is just reading the ohms, so if you have 158 it sounds like the sender is fine. I would check that reading all the way to the PCM (remember the wires are in two different plugs) From there the manual says that the signal is sent from the PCM across CCD bus circuits to the instrument paanel.

No idea how to help there. Sounds like you have good trouble shooting skills and are on the right track Good luck

 

[tractorface]

Half @$$ idea

If you really get stumped you could always install a older style aftermarket fuel gauge to work with the sender. It is easy to find 240/40 ohm gauges. They would work fine with your sender.

 

[Tcolesanti]

I obviously have a problem between the connector at the wheelwell and the pcm or the pcm to the gauge. Narrows it down a bit. Still, it is such a mess of wires. I probably won't be able to go any further until next week when this storm passes. Sunny California-yeah right!

 

[Tcolesanti]

Tractorface, I also wanted to say thanks for all your help, when I check it out next week I will let you know what I find. Thanks again

-Tom

 

[Tcolesanti]

O. k. here is the update. I took it to dodge and they got back to me that day, said it was the PCM. I told the service manager I wanted to talk to the mechanic so he could explain it to me. I talked with the mechanic, he said there were three separate tests done on the fuel level system. The PCM sends 12V to the sender, the sender regulates the voltage depending on the level of fuel and sends it back to the PCM. The PCM in turn converts this to a BUS signal and sends it to the gauge. My PCM was not sending a BUS signal. Changed the PCM, all is good now.