Gauges
Not clear on what you mean by the gas gauge & speed-o not working "properly". Do you mean they work but are unsteady, or just don't work at all, like the odometer????
Do you have a lit, or intermittently lit CEL, ABS, or OD light????
If you have a lit CEL, have the engine computer scanned for trouble codes & post All code Numbers, as maybe they can offer up good trouble shooting clues on the speed-o problem.
Most autoparts stores can/will scan the engine computer at no cost, but if you have ABS, or OD lights lit, a shop with a high end scantool will be needed to pull the ABS & Tranny trouble codes.
If you have an auto tranny, is its shifting acting out???? The reason for asking is that the auto tranny, speed-o & ABS use the rear ABS speed sensors PID output to do their things, so if its corrupt they too will likely act out.
On the fuel gauge, if its working at all, but just intermittent, sometimes its because of corrosion on the fuel level sensor & Chevron claims that its Techron Concentrate Plus can clean this corrosion & wake the sensor up. One of the autoparts stores has a bogo deal on Techron this month if you of a mind to try it. Even if it doesn't bring fuel level joy, it'll tidy up the fuel injectors, intake valves, piston crowns & heads of deposits & that's a good thing, so the gold spent for Techron isn't wasted!!!!
Some thoughts for consideration, let us know how it goes.








