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Discussion Starter · #1 ·
Hi all,
My fuel gauge always indicates "full", so I did some testing today with the gas tank off the bike.

  • The resistance of the sender changes as I tip the tank with some gas in it, so the float's moving, and probably working fine.
  • The brown wire at the connector (loom side) has a very low resistance to ground, which is correct.
  • However, shorting the connector, or (my first test) connecting a variable resistor across it and twiddling has no effect on the gauge. Always says "full".
Any ideas where I should look next? Maybe the connectors to the instrument pod?

Thanks!
Dan
 

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It looks like you've checked out the fuel level sensor successfully. I think you're correct in turning your attention to the instruments.

I'm looking at my manual for a 2002 Sprint, so keep in mind, things very well could be different between mine and yours, but here goes.

The fuel guage has a 4 wire connector. #1 is a green and black wire with a 10 ohm resister. #2 is a green and red wire with a 75 ohm resister. #3 is a black ground wire, shared with the illumination bulb. And #4 is a red and blue wire for the ilumination bulb. You could have a bad connection at the connector, a broken wire, loss of your ground. Turn your lights on and see if your fuel guage lamp lights up, that would tell you if #3 is connected to ground anyway. You can check your resistance on wires 1 and 2.

I really wish you had a manual because it provides some very detailed information on the fault codes and which pins to check the circuit at, and the wiring diagrams are very helpful.

For a 2002, the manual is showing:
P1620 Fuel guage system fault
P1621 Open circuit, or short circuit to earth
Both of these say to ensure the guage connection is secure, then disconnect ECM and proceed to test 1. Test cable and terminal integrity -ECM pin 1/A4. Faulty? Rectify fault. Go to test 5. OK, go to test 2.
Test 2, check cable for short circuit -ECM pin 1/A4 to earth. Short circuit? Rectify wiring fault. Go to test 5. OK, go to test 3.
Test 3, check cable continuity -ECM pin 1/a4 to fuel guage pin 1,
-Fuel guage pin 3 to earth, -Fuel guage pin to to alarm control unit pin 1. Open circuit? Locate and rectify wiring fault. Go to test 5. OK, go to test 4.

P1622 Short circuit to battery+
Disconnect fuel guage and proceed to pinpoint test 4.
Test 4, Check cable for short circuit, -ECM pin 1/A4 to ECM pin 2/E1. OK, replace the fuel gauge. Short circuit? Locate and rectify wiring fault. Go to test 5.

Test 5, Reconnect harness, clear fault code and run diagnostic tool funtion test to visually verify operation of guage. OK? Action complete. Fault still Present? Contact Triumph.

Like I said, this is from the manual for the 2002, so I don't know if the pin outs will be the same. You might have to wring out the wires.

This is a very good example of what happens when a mechanic with OCD has a manual and posts on a forum :D

Here's to hoping it's something simple. :D
 

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Be happy! It's better than reading empty and lighting the warning lamp with 1/3 of a tank left as these bikes do when everything is working "properly"...
 

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Discussion Starter · #4 ·
Oh, I'm happy anyway! :D

Thanks, Charlie - that's very detailed and much appreciated. I do have the Haynes manual, but not a service manual; and I don't (yet) have a cable to read the fault codes.

Anyway, next time I get some time I'll look into it more carefully.

Thanks!
Dan
 

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It may have the wrong tune loaded in. A Daytona tune (S3?) don't have a fuel gauge, so they don't send the signal to the gauge. It is more likely to be the sender or gauge but it is worth checking out

Rexx
 

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Please let me know what you find out. I am having the same issue. I put the TOR pipe on the bike and the dealership remapped it for me. It was running poorly so I asked them to put the stock tune back in and the fuel gauge didn't work after I picked the bike up. They thought it was the sensor so it was replaced and that didn't do anything so I think the dealership has done something electrical to mess up the gauge but I am not sure.
 

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Discussion Starter · #7 ·
It may have the wrong tune loaded in. A Daytona tune (S3?) don't have a fuel gauge, so they don't send the signal to the gauge. It is more likely to be the sender or gauge but it is worth checking out

Rexx
Hmmm, now that's an interesting thought! The bike did have a TORS pipe on it when I bought it, so maybe the map's not stock. That might explain why it's a little gutless at low revs...

Seems like another good reason to invest in a cable. :)
 

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I recall last year loading the Massive Midrange tune onto my Sprint just to have a go with it. Yeah, the gas guage read full when I knew I was low on gas. It's worth a look. Wouldn't it be nice if that's all it was?
On a side note, lateley on the forum, dealers loading the wrong tune seems to be a popular post topic.
 

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Someone posted a internal diagram of the fuel cell. Seems to me the guage is almost useless as it will show 3/4 or more full when you have less than a gallon. I just gas every 230 miles.
 
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