I have been working on a friend’s 1993 R1, which cuts fuel when it tries to boost. Unfortunately, it doesn’t have any error codes. We went through all of the vacuum hoses, and then we got around to checking the TPS voltages. The TPS voltage was a range of 2.6V-3.2V from no throttle to full throttle. Thinking the TPS was bad, we bought a new one and put it on. But, it is reading the exact same voltages.

We then took measurements from the individual wires on the TPS connector. With the TPS connector unplugged, we get the following voltages. The Black/Green wire reads 4.6V, the Brown/White wire reads 5V, the Green/Red wire reads 0V, and the Brown/Black wire reads 0V.

From looking at the wiring diagram, I would expect the Black\Green wire to read 0V, not the 4.6V we are getting, since it is one of the wires that inputs into the ECU from the TPS unit. Has anybody measured the voltages at the individual wires from the TPS connector?

 

Did you try following this
http://fd3s.net/tps_adjustment.html

 

Typically in a 3 wire TPS the middle wire is your refrence to the computer. Try back probing that connector with the TPS pluged in using a T-pin, place red lead from the DVOM on T-pin and the other on ground..now roatate TPS to WOT you should see close to 5v

 

nashman69g,

That was the procedure we used to first try to adjust the TPS. The TPS would not adjust more than .2V, which would only allow it to go from 2.5V to 2.7V with the throttle closed, and 3.1V to 3.3V with the throttle fully open. I measure the voltages by sticking a safety pin in the connector. I measured the voltages from the Black/Green wire and Green/Red wire as per the instructions. Both wires gave me similar results. I could never get the TPS to adjust down below 2.5V with the throttle closed or above 3.3 Volts with the throttle fully open. That is why I thought the TPS was bad.

I am concerned that the ECU is actually outputting voltage through one of the input wires. From looking at the wiring diagram page B-1c, the BR/W wire gives the Throttle sensor a 5V reference, the BR/B wire gives the sensor a ground path (0V). Then the BR/G wire and G/R wire each connector to a variable resistor in the TPS unit. With out the connector being in the TPS unit, both of these wires shouldn't have any voltage on them, if I am understanding the TPS operation correctly. I was hoping that someone else has measured the voltages at each of the 4 wires, with the connector unplugged, so that I can see if the computer is supposed to be putting 4.6V volts on B/G wire.

 

every wire except for the ground (BR/W) is putting close to 5V...

 

Thanks for the information, we may be having a problem with the Green/Red wire then.

 

Have you checked for codes? If you had a open circuit or stort in the geen/red wire a code should have be sent. Have you checked that the tab on the t/b is properly engaged with the tps? I would try removing the tps from the t/b with the connector still attach and see if you get the full range of voltage moving the tps by hand.

 

read his first post!

 

Busted be the posting police.

 

What's the resistance across the harness between the black/green and brown/white wire? I think you may have a short between them. I agree, that wire should carry no voltage.

Dave

 

I took some measurements on my 1994 model and saw that my Black/Green wire does read 2.4 Volts when it is disconnected from the TPS. So, it appears that it is normal to have voltage on this wire. Since the computer isn't giving us any TPS error codes, I think we will start looking at his fuel system, to see if there is a problem there.