100 Series subtank guage

Submitted: Sunday, Sep 05, 2021 at 14:36
ThreadID: 142523 Views:4624 Replies:3 FollowUps:3
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Hi all, have recently purchased a 2002 gxl (2uz). When switching to sub tank the guage drops to empty and low fuel light comes on, filled to the brim, same behaviour. It does run off the stub tank no problems.

Pulled out the sender, between two pins resistance changes between 180ish ohms and 0. Between another pair it goes from open circuit to closed. Assuming that's for low fuel light. Seems to me this is working? Have checked these values at the harness where the subtank meets the rear body harness, all seems ok there too (about 90ohm). Have tightened the screws in the cluster where the wires come in. No dice...

Assuming something is kaput in the cluster? Any other ideas appreciated!
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Reply By: RMD - Sunday, Sep 05, 2021 at 15:30

Sunday, Sep 05, 2021 at 15:30
I would be thoroughly checking ANY earthing to neg wiring and the fixing points to the body/chassis of those wires.
AnswerID: 637804

Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 05, 2021 at 16:15

Sunday, Sep 05, 2021 at 16:15
Matthew, your trouble-shooting is good and indicates that the sender and some wiring is OK to a point.
You need to extend that check to the instrument panel....... not a pleasant task I agree!!

A point of suspicion would be the tank changeover switch. It (or an associated relay) must incorporate a pair of contacts to transfer the sender signal before passing it to the gauge. There may be a poor switch contact or connection from the auxiliary tank.

Perhaps someone with an appropriate wiring digram could comment further?


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FollowupID: 915920

Reply By: Mathew E3 - Sunday, Sep 05, 2021 at 18:20

Sunday, Sep 05, 2021 at 18:20
I conceded a small defeat and ordered a new sender .... as much as I hate blind part swapping if it miraculously "just works" it'll save me digging around vehicle harnesses. At least then there will be one known good component...
AnswerID: 637807

Follow Up By: RMD - Sunday, Sep 05, 2021 at 22:10

Sunday, Sep 05, 2021 at 22:10
If the gauge work on main isn't the cluster working? The cluster only reads what it is sent, so it seems wiring/plugs or earthing is involved particularly on the change over components.
FollowupID: 915922

Follow Up By: Mathew E3 - Sunday, Sep 05, 2021 at 22:49

Sunday, Sep 05, 2021 at 22:49
Yeah main gauge is all good, looking at fsm it appears both senders go to cluster and the switch goes there too to tell the cluster which one to read rather than being switched externally anywhere.

FollowupID: 915923

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