RedimprezaOB Posted January 21, 2011 Share Posted January 21, 2011 So, this is a topic somewhat beat to death in some forums, but different.... My 04 impreza OB threw a CEL. I also noticed the low fuel indicator would come on and go off many times in a 20 minute drive....never mind a full or half full tank level. Code 0462 - Fuel Level circuit, low voltage input. Did the ohm meter on each sensor and the sensor circuit putting them in series, checks out ok. Dealer says rodents likely gnawed the harness and want 10 hours to pull the tank. I made a jumper harness to go from connector under rear seat to R58 on fuel tank. I also jumpered the level sensors completely by removing them from the circuit and adding 50ohms across the leads at the connector under the rear seat. No go, still getting the intermittent low fuel indicator. ??Anyone know what the voltage should be in the low fuel thermistor circuit?? But oddly, the fault code is the level sensor. ??thoughts, observations?? Thanks Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 21, 2011 Share Posted January 21, 2011 Check out www.brighterideas.com Dan's training videos highlight how poor a resistance check is and how your voltmeter can lie to you. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 21, 2011 Share Posted January 21, 2011 I still cant find my leggo book Everyone is shooting at flies here. Everything grounds through the tank. The light reacts much quicker then the gauge does (pump has its own circuit). The light operates by sensing the tmep of the fuel around it, in theory the fuel is colder then the air in the tank 11 months out of 12. The colder it is outside and the longer it is cold, the less acurate the light is, the inverse in summer. The sensro is a thermister so it is not just as easy as putting a ohm gaunbe on it. BTW OHM meters may be inacurate, but they are good enough for 98% of the people that use them as there is a relativly high tolerance built inot non-military specs. I would just put a jumper from the tank itself (sealed of course) to a ground and start there. Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 22, 2011 Share Posted January 22, 2011 I agree with Nipper. Try adding a ground jumper to the connector wire at the tank tieing to ground and see if that makes a difference. If it does then repair the faulty ground connection. Quote Link to comment Share on other sites More sharing options...
RedimprezaOB Posted January 23, 2011 Author Share Posted January 23, 2011 No real development on this issue as of yet, chores, bicycles, whatnot. However, I ran an interim harness as described in the first post from the connector under the seat to the R58 connector on top of the fuel tank. The level sensors were not connected opting instead for my ohm gaunbe.... Been getting good use of this word...thanks Nipper! For some reason I opened connector R59, the sensor on the sub tank and went about my errands. 3 drive cycles CEL cleared and there had been no low fuel warning flashes. That was odd because it was not even in the active circuit. Drove to emissions and got my new tags! Not a 1/2 mile from the emissions center on the way home CEL and low fuel lamp!! Doh! Intermittents are no fun. So, you guys think there could be some type of grounding issue? I'm reasonably sure I have not seen a ground strap from the tank itself. I'll try running a ground but from what I know the FP has its own 12V circuit. That obviously works. The Thermistor circuit I cannot find an exact circuit schematic. Some show One line in and connectivity to a fuel level sensor. I have 2 wires for FP and 2 wires for level sensor and 2 wires I assume are for the thermistor on R58. All schematics show the thermistor run to a "micro computer". So, if the thermistor is really a temperature controlled resistor, is there really any reason I couldn't place a resistor gaunbe (again thanks) into the circuit to eliminate the real one as a culprit?? Quote Link to comment Share on other sites More sharing options...
nipper Posted January 23, 2011 Share Posted January 23, 2011 There is a such a thing as "too much information" Look at a Haynes manual, that makes a pretty good translator from OE speak to Anyone else speak. Hell I get lost in the OE manuals, especially schematics for subaru as I find them tougher to read, especial a digital copy. Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 23, 2011 Share Posted January 23, 2011 After looking at the service data again I noticed the wiring to the senders also ties to the ECU on connector B135. Perhaps there is a bad connection at that point. Try reconnecting that connector and see if that helps. Quote Link to comment Share on other sites More sharing options...
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