Measuring TPS Voltage

Rickd · 08-21-2000, 07:17 AM

A while back I posted a question about accessive idle speed. Any time the car was moving the idle speed would stay at 1500 rpm. Someone suggested that the TPS might be out of whack. I remembered that I had printed off a thread from Joel Gat stating that the TPS voltage should be between 0.4-0.5 volts at throttle, but he wasn't sure what wires to measure between on a newer RS.

I found the wires with some trial and error, and here is the results.

To start out with, the connector on the TPS is positioned so that you can't get at it to stick a multimeter probe in without removing the large airbox on the t/b. After removing the connector, I took a paper clip, cut it into 2 pieces, sharpened up on end on each piece, and inserted the clips into the connector from the back side. The wires you need to probe are the 2 middle wires, white/red & black/red. (there are 4 in total on my 99RS). Check continuity of the paper clips with an ohm meter, and re-install the connector. Start the car, let it idle, and measure the voltage using the positive lead on the voltmeter on the white/red wire, and the negative lead on the black/red wire. Mine measured 0.51 volts. I backed off the TPS until it was reading between 0.48-0.49 volts. End of problem. Now my only question is why after 37,000 km did my TPS suddenly change?

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jhuang76 · 08-21-2000, 04:20 PM

It could be due to the TPS sensor slipping a little. It looks like Subaru put some white locking compound to prevent slipping. I've noticed that since I've adjusted the TPS, it has slipped .04 volts.

Orbiter · 11-08-2000, 02:43 AM

hey i just read that skidazzle posted the subaru shop manual says our cars should read
.2v-1v at closed throttle, and
4.2-4.7 at wot..

is this correct? or typo?

joel u there?

08-21-2000, 07:17 AM	#1
Rickd Scooby Newbie Member#: 323 Join Date: Sep 1999 Location: Winnipeg, Manitoba, Canada Vehicle: 1999 Impreza RS Rally Blue	Measuring TPS Voltage A while back I posted a question about accessive idle speed. Any time the car was moving the idle speed would stay at 1500 rpm. Someone suggested that the TPS might be out of whack. I remembered that I had printed off a thread from Joel Gat stating that the TPS voltage should be between 0.4-0.5 volts at throttle, but he wasn't sure what wires to measure between on a newer RS. I found the wires with some trial and error, and here is the results. To start out with, the connector on the TPS is positioned so that you can't get at it to stick a multimeter probe in without removing the large airbox on the t/b. After removing the connector, I took a paper clip, cut it into 2 pieces, sharpened up on end on each piece, and inserted the clips into the connector from the back side. The wires you need to probe are the 2 middle wires, white/red & black/red. (there are 4 in total on my 99RS). Check continuity of the paper clips with an ohm meter, and re-install the connector. Start the car, let it idle, and measure the voltage using the positive lead on the voltmeter on the white/red wire, and the negative lead on the black/red wire. Mine measured 0.51 volts. I backed off the TPS until it was reading between 0.48-0.49 volts. End of problem. Now my only question is why after 37,000 km did my TPS suddenly change? * Registered users of the site do not see these ads.

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08-21-2000, 04:20 PM	#2
jhuang76 Scooby Newbie Member#: 1284 Join Date: Apr 2000 Vehicle: 2005 Legacy GT Royal Blue Pearl	It could be due to the TPS sensor slipping a little. It looks like Subaru put some white locking compound to prevent slipping. I've noticed that since I've adjusted the TPS, it has slipped .04 volts.

11-08-2000, 02:43 AM	#3
Orbiter Scooby Specialist Member#: 66 Join Date: Jul 1999 Location: Vancouver, British Columbia, C Vehicle: 2002 Impreza WRX Britney Edition	hey i just read that skidazzle posted the subaru shop manual says our cars should read .2v-1v at closed throttle, and 4.2-4.7 at wot.. is this correct? or typo? joel u there?