1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

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1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby blue_rodeo » Tue Jul 24, 2012 11:54 pm

First off, I have searched and Googled, and searched again. So my wife's 98 Rodeo's gas gauge hasn't worked in a while. First, the gauge cluster had gone on the fritz a while ago and ended up getting it replaced. The speedo and fuel gauge didn't work on that one. On the new one, the speedo worked again but the fuel gauge still didn't work. So I assumed that it was the notorious fuel sending unit problem. I held off getting it fixed and finally ordered the whole new fuel pump/ sending unit assembly. I dropped the tank hooked it all up, and the fuel gauge still does not work. (And yes it has gas in the tank) I'm not sure where to go from here. I have another cluster that I am going to try tomorrow and see if it is maybe just the gauge. If that is not it, does anyone know where the sending unit wires go to, to find out if it is a wiring issue? Thanks
- 1995 Rodeo 4x4 (Sold)
- 1998 Rodeo 4x4 Base (Wife's Daily Driver)
- 1998 Rodeo 4x4 LS (Current Project)
- 1999 Dodge Durango SLT (My Daily Driver)


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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Buster28 » Wed Jul 25, 2012 6:25 am

The PCM provides a +5VDC reference voltage to one side of the fuel tank sending unit which is a variable resister with a resistance range of 80 to 290 Ohms, the return side of the sending unit is connected to the PCM.

The +5VDC sending unit reference voltage supplied by the PCM is connected to a pull-up resistor in the PCM, so electrically the sending unit (variable resistor) is in series with the pull-up resistor and the return in the PCM. This configuration creates a voltage divider so the voltage the PCM fuel gauge circuit senses varies with the fuel level. As the fuel level decreases the sending unit resistance increases causing more of the + 5VDC to be dropped across the resistance of the sending unit. When fuel is added, the resistance decreases and less voltage.

When this circuit is open due to broken wires or an open in the sender DTC P0463 will be set and the CEL will be ON. Since you do not have this DTC set, you probably have a problem related to the gauge cluster.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Gizmo42 » Wed Jul 25, 2012 8:10 am

Its simpler then that. Some rodeos have to have the PCM flashed with an upgrade program in order to read the new fuel sending unit. Most often its '98s that need to have it done but not all do. If you cant find an isuzu service garage in your area, any honda dealership can do it since the passport is a rebadged rodeo and has the same issue.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby blue_rodeo » Wed Jul 25, 2012 6:36 pm

So I switched out gauge clusters today. Now with the float all the way up the gauge moved up to about 1/8 of a tank and the fuel light went off, but it still isn't working properly. I made an appointment at a former Isuzu dealer here in town for tomorrow. Do you think that the PCM just needs reflashed and should they be able to do it?
- 1995 Rodeo 4x4 (Sold)
- 1998 Rodeo 4x4 Base (Wife's Daily Driver)
- 1998 Rodeo 4x4 LS (Current Project)
- 1999 Dodge Durango SLT (My Daily Driver)


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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Gizmo42 » Wed Jul 25, 2012 8:32 pm

Sounds to me like thats all it is. As long as they are still an Isuzu service center (most former dealerships are) and have all the stuff to do it, should be no problem.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby blue_rodeo » Mon Jul 30, 2012 11:53 am

Thanks for all of the help guys, got it all fixed!
- 1995 Rodeo 4x4 (Sold)
- 1998 Rodeo 4x4 Base (Wife's Daily Driver)
- 1998 Rodeo 4x4 LS (Current Project)
- 1999 Dodge Durango SLT (My Daily Driver)


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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Gizmo42 » Tue Jul 31, 2012 12:21 am

Did you have to get it reprogrammed?
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby blue_rodeo » Tue Jul 31, 2012 12:31 am

Yeah they had to reprogram it
- 1995 Rodeo 4x4 (Sold)
- 1998 Rodeo 4x4 Base (Wife's Daily Driver)
- 1998 Rodeo 4x4 LS (Current Project)
- 1999 Dodge Durango SLT (My Daily Driver)


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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby mossyoakjim » Mon Aug 20, 2012 6:37 pm

Hey Buster 28 or anyone else that might be able to help.... where do i check the ohm range on the new module? i had to replace the fuel module assembly and now my fuel gauge is not working. I carried it to the local isuzu dealer to get it reflashed after reading this post but they said it was the wrong part or installed incorrectly. I thought i took my time when installing the new one and have rechecked my wires but its still not working? Any help will be appreciated.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Buster28 » Tue Aug 21, 2012 5:47 am

You would measure the resistance across the two leads that go to fuel sending unit, difficult to do with the tank in place and the resistance you measure would depend on the amount of fuel in the tank so that is not much of a test. You could measure the resistance at the PCM as well, but you would need a schematic to figure out which pins.

Did the gauge work before you replaced the sending unit?
Why did you replace the original fuel sending unit?
What replacement brand did you use?
Is the CEL ON?
Does the low fuel indicator work?
Does the gauge show any reading at all?
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby mossyoakjim » Tue Aug 21, 2012 1:55 pm

The old gauge would work occasionally. I replaced the whole fuel pump module so it had the new sending unit on it. It was a delphi unit. No CEL, the fuel light does work and it will read about an 1/8 of a tank when completely full.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Buster28 » Tue Aug 21, 2012 6:19 pm

Based on your information I think you wired the unit correctly, if the wires from the PCM to the sending unit were open the CEL would be on, a DTC set, and the low fuel indicator would not work.

I think the actual problem with the 98 model is that the algorithm in the PCM firmware that controls the fuel gauge is not compatible with the new fuel sending units and a new version of the firmware needs to be loaded into the PCM You could try a Honda dealer, a 98 Passport would have the same issue so they will have the necessary equipment.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby ammon91 » Mon Aug 26, 2013 10:05 pm

I have called every possible Isuzu/honda dealer around the Allentown Pennsylvania area and no one has the equipment to reflash. I was referred to dealers in Harrisburg, Reading, and Scranton with no luck. Anyone have a idea of somewhere that can still do the reflash of my 98 Rodeo PCM?
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Buster28 » Tue Aug 27, 2013 5:45 am

Par-Tech, Inc. 139 Ellen Drive Lake Orion, MI. 48359 (248) 276-0213, used to advertise to do the job for $55.00.
Apparently Ellen Drive was renamed Premier Drive : www.partechgss.com
Par-Tech, Inc. 139 Premier Dr Lake Orion, MI 48359 (248) 364-0215
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby mutts » Mon Sep 02, 2013 4:12 pm

Will a broken unit register anything? Mine also shows 1/8th when full andvthen CEL. Perhaps mine needs reflashing
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby Buster28 » Mon Sep 02, 2013 4:37 pm

If the CEL is illuminated there is a stored DTC, best starting place is to retrieve the trouble code and see what it is reporting and proceed from there.
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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby boknows20 » Sun Jun 29, 2014 3:20 am

I just replaced my FSU and need my PCU updated. I've contacted all the local dealerships in a 500 mile radius with no success.

Has anyone had any luck with Par-Tech?

Anyone have luck with a non dealership update?

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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby dlatulip » Thu Jul 17, 2014 10:06 am

I am in the same boat, I can't find anyone to program my 1998 Rodeo after changing the fuel pump and sensor. Is there any other work arounds? Is it possible to remove it from the rodeo and send it somewhere? Where?


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Re: 1998 Rodeo Fuel Level Sender Problem...Maybe Gauge?

Postby boknows20 » Thu Jul 17, 2014 3:46 pm

I just sent mine to Par-Tech, http://isuzusource.com/v2/service_techn ... cement.php , and just got it back on Monday.

This the form I used, http://techinfo.honda.com/rjanisis/pubs ... 20Form.pdf , but I think you will be able to use the link above and pay online.

It cost $125.00, They received it on Thursday and I got it back on Monday.

It was awesome to see the gas gauge go to full!


PS. I purchased a PCM of ebay ($35.00) and installed it in my passport while I shipped my OEM to them for programming since I still wanted to use my truck while it was shipped.


Let me know if you have any questions.

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