R1 dash showing 0 mph constantly.
james h - 20/9/15 at 09:29 PM
For some time now my speedo has not been working. I have replaced the ICU (due to the old one causing the engine to run on 2 cylinders), and swapped a
speedo sensor for a used eBay item. Still no joy.
Has anyone had this issue before? It is a 5JJ engine and clocks.
Continuity for all wires from the sensor is good. There are no self-diagnostic error codes. I bypassed the speedohealer with no result.
However, I did the Haynes recommended test on the sensor, and the voltage varies by 11.15-11.05V when rotating the rear wheel in neutral, rather than
0-5V as it should.
Could I have been unlucky in buying another duff sensor? Or are my clocks gone?
I'm posting here on the offchance somebody else has come across the same issue. I don't want to fork out any more money on a sensor, and
certainly not on some expensive clocks 
James
CosKev3 - 21/9/15 at 04:39 AM
I've got some 5jj clocks spare if you want to try them?
I'll check voltages from my sensor when I grab a new Multi meter
james h - 21/9/15 at 07:26 AM
That would be incredible, thanks! I'll send a u2u
britishtrident - 21/9/15 at 05:43 PM
If like most modern speed sensor it is a Hall Effect device it is in effect a switch the output is either on or off best way to test them is with an
osciloscope but from your description it looks like the replacement sensor is blown.
[Edited on 21/9/15 by britishtrident]
james h - 21/9/15 at 07:41 PM
quote:
Originally posted by britishtrident
If like most modern speed sensor it is a Hall Effect device it is in effect a switch the output is either on or off best way to test them is with an
osciloscope but from your description it looks like the replacement sensor is blown.
[Edited on 21/9/15 by britishtrident]
I was wondering if the trigger for the hall effect sensor had fallen off (if that is even possible - I suspect it looks at a machined/cast part of the
gearbox output shaft).
Why does diagnosis of electrical stuff have to be so bloody annoying?!?
britishtrident - 22/9/15 at 10:39 AM
I came to the conclusion about 10 years when trying to trackdown ABS fault that an oscilloscope was getting essential for tracking down sensor
faults. I have a couple at the moment both very cheap Chinese ones that electronics buff would consider toys but both cost under £60. One of them is
a tiny DSO201 nano that fits in the palm of my hand ideal ideal for this kind of job.
This you tube video shows tracking down a hall effect crank sensor fault using an oscilloscope -- the sensor is very similar to your speed sensor.
Hall Effect sensors come in two styles 3 wire and 2 wire only difference is the 2 wire type ground through the mounting bolt.
Link to ScannerDanner Youtube vid