Only showing 0.6V from the ODBII port-post-4-fix

[Lightning-E]

While trying to diagnose why I can't seem to get FDRS to connect, I noticed in the logs that it's detecting 0.6V and triggering a low voltage error and cancelling the connection. Sure enough, I see 0.6V in the lower right corner of Forscan as well. This is with the truck on or off. Obviously, it's not at 0.6V. The wires at the back of the plug seem fine. Tried wiggling the plug, it seats all the way and clicks, no play in it. Any ideas on what to check?

Update: it was a blown fuse. #160 to be specific

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[RLXXI]

While trying to diagnose why I can't seem to get FDRS to connect, I noticed in the logs that it's detecting 0.6V and triggering a low voltage error and cancelling the connection. Sure enough, I see 0.6V in the lower right corner of Forscan as well. This is with the truck on or off. Obviously, it's not at 0.6V. The wires at the back of the plug seem fine. Tried wiggling the plug, it seats all the way and clicks, no play in it. Any ideas on what to check?

Should be a fuse for that. Couldn't say which one for your year model, on a 2025 it's fuse 160, 10A. Check them all to be sure.

 

[chl]

Did you check the voltage with a voltmeter - that'd be my first step.

If the voltage at the business end of the cable is low, might be a bad cable with some kind of short or broken wire causing a voltage drop. But check the cable pin-by-pin end-to-end for unusually high resistance using the ohms setting (or a continuity tester) should be almost 0 ohms end-to-end or a strong continuity light indication.

If the cable is ok and the voltage is low at the truck side, you might have a problem somewhere between the battery and the outlet - bad wire?

If the cable is ok move on to next step.

Is there anything else on the same circuit - another device drawing power could cause a voltage drop - that'd be my second step if the cable is ok. Unplug/turn off any other things that could be drawing power on that circuit.

Are other circuits, like the various USB and cigarette lighter outlets showing the correct voltage with the voltmeter - that'd be my third step . If other circuits are ok, then likely not the 12v battery, and more likely a a bad connection from battery to the FDRS outlet.

A weak 12V battery has been known to cause FDRS troubles per posts on the forums, and these batteries in the Lightnings have been problematic due to the way trickle charging is handled (or not handled) by the truck.

Of course there could be some software glitch, which is a whole other ball of wax.

 

[Lightning-E]

Should be a fuse for that. Couldn't say which one for your year model, on a 2025 it's fuse 160, 10A. Check them all to be sure.

This was it!!! I figured since there was any voltage that it wasn't a fuse. I was wrong. It's currently updating!

 

[chl]

This was it!!! I figured since there was any voltage that it wasn't a fuse. I was wrong. It's currently updating!

That is strange, I would have thought the same thing - open fuse, no voltage at all.
Glad it was something so simple!
Of course 0.6v could have been a misread of the actual voltage - digital voltage checks can float around a bit near zero where the precision is low.

 

[RLXXI]

A 12v test light is a better choice of tools when checking fuses. .6v will not light it up.

 

[Lightning-E]

I wonder if it wasn't reading voltage off one of the other wires?

 

[RLXXI]

I wonder if it wasn't reading voltage off one of the other wires?

Not likely. Probably just the meter itself and/or it's calibration.

 

[Lightning-E]

Not likely. Probably just the meter itself and/or it's calibration.

This was in FDRS and ForScan.

 

[RLXXI]

This was in FDRS and ForScan.

Random voltage. Always use a test light on fuses.

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