Early sign of fuel sending unit failure

[Alaskaskiff]

My second sending unit in my fuel tank is just starting to lose accuracy. Just checked the stored codes yesterday and noticed a 42 code (applicable to 94-97 trucks). Got this last time as well when sender was going bad. Three symptoms in the sender could generate the code:



Fuel sender volts too high



Fuel sender volts too low



No movement of sender over a certain number of miles





Appears to be an easy way of telling that the sender is going bad.



I check the codes periodically, just to see what is going on. No tools required!!

 

[OMitch]

how do you check the codes??

 

[Alaskaskiff]

Checking engine codes

Don't know about post 97 trucks, but on the older ones (94-97) you cycle the key with the truck off rapidly from acc to run twice in under two seconds, then leave it on run and the codes will flash out numerically on the check engine light. They typically start with a 12 (1 flash, 2 flashes) for a power disconnect, then will flash out codes after that. It does two sets of five flashes when done.