read a dropping voltage from the throttle position sensor

1994 OLDSMOBILE BRAVADA
146,000 MILES
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PAULHOMERJR
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What could be causing an analyzer to read a dropping voltage from the throttle position sensor as the RPM increases? I have replaced the TPS three times and the PCM yet the analyzer still continues to say the TPS is bad and shows the voltage dropping as I increase the RPM. It doesn't shift until above 2500 RPM and then shifts very hard. It also is running 200 RPM faster than normal at highway speeds even though it is in OD.
Jul 16, 2012 at 5:57 PM
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DOCFIXIT
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What code is comming up?
Jul 16, 2012 at 6:01 PM
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PAULHOMERJR
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22 TPS Sensor Low
Jul 16, 2012 at 6:32 PM
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DOCFIXIT
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Will need a DVOM see diagrams back probe TPS connector Black lead on bottom sensor ground and middle one RED probe. Key on at idle voltage less than 1 volt(.5 v best). then operate throttle from idle to full meter should go up steady to 4.5 V
Jul 16, 2012 at 6:43 PM
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DOCFIXIT
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opps
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Jul 16, 2012 at 6:44 PM
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PAULHOMERJR
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It starts out at.27 and drops as the throttle is opened.
Jul 16, 2012 at 6:54 PM
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DOCFIXIT
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Check reference voltag must be 5V
Jul 16, 2012 at 7:03 PM
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PAULHOMERJR
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Reference voltage is 5.02. Checked the ground and it's fine also. The low voltage has been the same for all 3 new TPS.
Jul 16, 2012 at 7:45 PM
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DOCFIXIT
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Makes no sence if have 5v REF all TPS is a variable resistor so you say at idle .27v and as open throttl goes to zero
Jul 16, 2012 at 7:52 PM
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PAULHOMERJR
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My point exactly. Could this be an issue with one of the tranny sensors?
Jul 16, 2012 at 8:00 PM
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DOCFIXIT
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Unplug tps use jumper wire from 5v ref and then jumper ground on bottom wire hook up meter across ground and TPS signal open throttle what does it do?
Jul 16, 2012 at 8:35 PM
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PAULHOMERJR
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I figured out the problem. I bought the vehicle used and the engine had been replaced before I got it. The EFI was off of a 93 S-10 Blazer. Although the TPS looked the same, the throttle operates in the opposite direction. It took some research at the parts store but we got the right part and everything's perfect now. Thanks for your help. Have a great day.
Jul 18, 2012 at 9:19 PM
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DOCFIXIT
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Well don't that beat all and explains the weird readings
Jul 19, 2012 at 7:40 PM