Autosport Labs

Hi,
I have just installed MJV4 on my UK oval racer and the installation all went well until I tried to calibrate the TPS, On the configurator it shows the throttle fully open even with the TPS disconnected. I have checked with a volt meter and I have 5 volts at the Vref and TPS pins, Is this normal or do I have a fault somewhere as I would imagine that the Vref should be a 5 volt supply and the TPS pin is the voltage back from the sensor.
Any help will be grately appreiciated. thanks Andy

Have you definitely got a TPS version ECU rather than the MAP sensor version?

I am pretty sure it is as there is no place for a pipe on the MJ and inside on the board there is no map sensor and just a row of components on the TPS part of it

Hi Andy,

Are you checking the voltages with the megajolt unit unplugged completely from the wiring harness? You can power the unit temporarily with a 9V battery or something similar, just for the test.

Hi
I havent tested it in this way yet but all wires when tested were not connected to the tps and i just noted the 5volts from both vref and tps pins
Thanks

Hi Andy,

I understand you're confident about your cabling / wiring, but it's a good step to do when eliminating variables.

In addition to checking voltages at the connector, you can also do the following while powered up, connected & communicating with the configuration software:

jumper TPS_INPUT and GND. What does the load gauge show on the configuration software?
jumper TPS_INPUT and VREF. What do you see now?

Thanks for going through this- this is a good, definitive step towards determining where the fault lies.

While doing this test it's important you use a fairly feeble power supply, like a 9V battery, to reduce the chance of damaging something in case there's a mis-wire or slipped connection.

Let us know what you find out-

Thanks for this help guys, I will check this tomorrow and report back

brentp wrote:Hi Andy,

Are you checking the voltages with the megajolt unit unplugged completely from the wiring harness? You can power the unit temporarily with a 9V battery or something similar, just for the test.

Hi

Although I havent had much time the last few days to try everything you suggested, I have powered up the unit independant of the wiring harness with a sensor simulator which I have in the workshop. I set it to supply the unit with 5 volts (which is the maximum it can go) and then tested voltages again at the vref and tps pins and at both pins I had 1.6 volts. I will try in the next couple of days to try as you suggested about grounding these pins out and seeing what happens on the configurator

Thanks

hi
I have now powered the unit up with a 9v battery and connected to the configurator.
when i bridge tps and vref nothing happens on the screen and tps stays at 100% but when i bridge tps to gnd then the tps goes down to 10%

thanks
Andy

That is about the expected behavior. Connecting the TPS input to ground is 0 volts, and the default calibration puts that about 10%. That's equivalent to the throttle being 'closed' when connected to the TPS.

With the TPS left unconnected, or connected to VREF it should show near 100%.

I suspect either the TPS is either faulty or mis-wired. What TPS unit are you using?

Thank you so much for that, now i know i have a healthy controller i can get my tps sorted. I am using a 3 wire tps off a vauxhall corsa