TPS question



It seems that my FAST is not reading the TPS correctly. It will not read more than 9% at WOT. I have ohm'd it out and it reads low to high very smooth with no dead spots.

Not sure what the output of the FAST unit should be, I my guess is it like the stock GM setup of 0 to 5 volts.

Across A and C of the plug I only get .027 volts.

Is this correct or is there a better check to see if it is the box or the TPS.

If it is the ECU, where do I send it? What is the turn around time for repairs.

Hey Chris,

Don't know the actual answer off the top of my head, but if you do need to send it in to FAST, their turn around time is excellent. I smoked a part of my ignition output circuit last spring, and they had the unit fixed and sent back to me in a day. I sent it in on a Wednesday and had the unit back in hand on Friday.


Upon looking at Installation Manual and the dashboard it looks like the 5 Volt power supply in the ECU is OOC, the MAP is not giving a correct reading on the dash and it is reading 27 volts for battery voltage (digital volt meter is reading 11.8 volts).

If this is true, where do I send the unit for repair.
Check your wiring carefully and disconnect the TPS and MAP sensor while observing the readings. It's very unusual to lose the voltage reference as it's short circuit protected. It may well turn out to be a faulty MAP sensor or wiring shorting the reference supply voltage.

If problems persist, talk to your dealer or Call Craig at (810) 225-2700 and ask for an RMA number.


Is there any other sensors that use the 5v ref?

Is it protected by a fuse?

Only the MAP and the TPS use the raw 5V reference signal. The coolant and air temp sensors use it but through an internal pull-up resistor. So only the MAP and TPS can create a situation (externally) that causes the 5V ref supply to shutdown. Internally, the A/D converters use the 5V ref supply as a voltage reference for ratiometric conversions. So if the reference supply is shutdown, all A/D conversion will be in error. There is no fuse to protect it because it is self-protected. As long as the short exists, it will stay shutdown. The problem could be an external short, an internal short, or just a faulty component.

THANKS, you were correct, on the 3S-GTE engine the valve cover is rather large. I had it off and when I put back down I pinched the MAP wires and the hold down bolt cut into the 5v reg wire.

I cut out the bad wires and spliced in new and all the sensors are reading correctly again.

Thanks for the help. This board has been the greastest help with this system.