Possible TPS fault

andydawson475 · Post by **andydawson475** » Sat Mar 05, 2011 9:17 pm

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

cng1 · Post by **cng1** » Sat Mar 05, 2011 9:39 pm

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

andydawson475 · Post by **andydawson475** » Sat Mar 05, 2011 9:46 pm

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

Post by **brentp** » Sat Mar 05, 2011 9:51 pm

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.

andydawson475 · Post by **andydawson475** » Sat Mar 05, 2011 10:00 pm

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

Post by **brentp** » Sat Mar 05, 2011 10:42 pm

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-

andydawson475 · Post by **andydawson475** » Sat Mar 05, 2011 11:07 pm

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

andydawson475 · Post by **andydawson475** » Tue Mar 08, 2011 9:24 pm

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

andydawson475 · Post by **andydawson475** » Thu Mar 10, 2011 8:46 pm

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

Post by **brentp** » Thu Mar 10, 2011 9:27 pm

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?

andydawson475 · Post by **andydawson475** » Thu Mar 10, 2011 9:34 pm

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