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Hi, hoping someone can help me understand this!
My motorbike digital speedo sometimes fails and simply reads zero … probably 1 in 3 rides. If I switch the bike off, and restart, it usually works fine.
The speedo works by a rotating magnet near the hub sending a signal to the ECU. There are 3 wires – a live, a ground and then the 3<sup>rd</sup> which sends the signal. I’ve bought a Tuneecu diagnostic tool and it reads the error as ‘P1502 Speedometer driver – short circuit to positive’.
As far as I can see, the wiring all looks very clean and in good shape, it plugs into the ECU loom very nicely and cleanly.
I don’t understand the short circuit to positive?
Anyone help?
Thanks
(It’s a 2002 Triumph Speed Triple 955i)
It means the positive is shorting to ground before it gets to the sensor - check wiring for damage or replace sensor.
Thanks, and keen to understand ... so when I switch the ignition on, 12V is sent from the battery along the positive, but e.g. there's corrosion/mositure on the wire or the positive wire is frayed and touches the frame, so 'shorts' ... is that kinda the idea?
Yep, the 12v isn't reaching the sensor, my guess is a new sensor might come with a cable attached & sealed to make it waterproof at the wheel end so should fix the problem of cable or sensor.
It would be ideal if you could try one off a similar bike to confirm before buying a new one.
Great, got it. And I think I could cannibalise a friend's bike to trial a different sensor and wire. Thanks
'P1502 Speedometer driver – short circuit to positive’.
I read that as the *input* to the tacho is short circuited (i.e. connected to) positive - possibly by moisture inside the tacho, sensor, cable or connectors.
Well, switched the wheel sensor + cable to a know good one, and still getting intermittent zero.
So thinking of tracing the power feed to digital Speedo I it itself, but surely if this was shorting, it'd be blank rather than displaying zero?