2001 Isuzu Rodeo Fuel Gauge not working

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2001 Isuzu Rodeo Fuel Gauge not working

Postby Kyle56403 » Thu Dec 24, 2020 11:51 pm

I have a 2001 Isuzu Rodeo and when I bought it the fuel gauge wasn't working, so I read up and found out that the sending unit goes out on these cars sometimes. So like anyone would do I replaced the sending unit and... Still no fuel gauge. I was wondering if there's another problem or if I need to get my ecu reprogrammed or something of the sort.
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Re: 2001 Isuzu Rodeo Fuel Gauge not working

Postby Shawn Anthony » Fri Dec 25, 2020 1:39 am

The fuel sending unit is just one of 14 individual parts located in the system. The ECM is in no way connected to the fuel gauge system.

The first step in proper troubleshooting is to verify continuity of the circuit.
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Re: 2001 Isuzu Rodeo Fuel Gauge not working

Postby Buster28 » Fri Dec 25, 2020 4:05 am

A 2001 Rodeo does not have an ECM but it does have a Powertrain Control Module (PCM). The resistance value of the fuel level potentiometer (80-270 ohms) is measured by the PCM. The PCM converts the fuel level potentiometer resistance value into a fuel gauge signal.

Reprogramming the PCM after changing the fuel level potentiometer is necessary in some 98-99 Rodeo's because they originally had a 17 to 120 Ohm fuel level potentiometer and the replacement is 80-270 ohms.

You will have to do some electronic troubleshooting to sort out this problem. Start by making sure the H-5 body connector (Left Fender) is tight.

Btw, the PCM combines the Engine Control Module (ECM) electronics and the Transmission Control Module electronics (TCM) into single electronic module.

Click on schematics to expand.
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Re: 2001 Isuzu Rodeo Fuel Gauge not working

Postby mudoilngears » Sun Dec 27, 2020 7:45 pm

Shawn Anthony wrote:The ECM is in no way connected to the fuel gauge system.

Yes it is. The gauge is “driven” by the PCM, not directly by the lever sender.
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Re: 2001 Isuzu Rodeo Fuel Gauge not working

Postby Kyle56403 » Sun Jun 13, 2021 10:18 pm

Buster28 wrote:A 2001 Rodeo does not have an ECM but it does have a Powertrain Control Module (PCM). The resistance value of the fuel level potentiometer (80-270 ohms) is measured by the PCM. The PCM converts the fuel level potentiometer resistance value into a fuel gauge signal.

Reprogramming the PCM after changing the fuel level potentiometer is necessary in some 98-99 Rodeo's because they originally had a 17 to 120 Ohm fuel level potentiometer and the replacement is 80-270 ohms.

You will have to do some electronic troubleshooting to sort out this problem. Start by making sure the H-5 body connector (Left Fender) is tight.

Btw, the PCM combines the Engine Control Module (ECM) electronics and the Transmission Control Module electronics (TCM) into single electronic module.

Click on schematics to expand.

Hey so I know it's been a while but I was wondering if a short in the wire going from the sending unit to the PCM that sends the fuel level input (the orange/green wire I believe it was) could cause the gauge to not work.
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Re: 2001 Isuzu Rodeo Fuel Gauge not working

Postby Buster28 » Mon Jun 14, 2021 6:18 am

The Orange/Green wire is the signal side of the sending unit potentiometer. The Blue/Yellow wire is the signal ground side. When the tank is full the resistance the PCM sees is about 80 ohms. If the Orange/Green wire is shorted to ground the resistance the PCM sees is zero ohms (or close to zero), since zero is out of range the PCM cannot process the signal so the gauge does not indicate correctly.
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