Low voltage TPS
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 4,575
Likes: 369
From: Ozark, MO
C5 of the Month 6/13
Low voltage TPS
I replaced the throtle position sensor on my 92 and it caused the car to idle faster around 1,200 rpms and the computer threw a code 22, so I replaced the sensor again thinking I bought a bad sensor. Unfortunely, the new sensor didn't fix the poblem. So, yesterday I had a friend hook up his scan tool and it's giving a reading of zero volts for the tps. What could cause the sensor to have low voltage and how would you correct this problem.
Le Mans Master
Joined: Apr 2005
Posts: 8,077
Likes: 4
From: Scarborough ONTARIO
I dont know how LT1 Tps works but 65z01's website has excellent info on setting IAC and TPS very easy to do it just Torx screw driver and multi meter and pin to snap to ALDL connection, here is site :
http://www.geocities.com/jgkov/TPSService.html
His website is devoted 85-91 TPI motors but should be similer to ur's i guess, hope some one will chime in.
In Tpi motors if idle voltage is too high it will set 21 code.
http://www.geocities.com/jgkov/TPSService.html
His website is devoted 85-91 TPI motors but should be similer to ur's i guess, hope some one will chime in.
In Tpi motors if idle voltage is too high it will set 21 code.
Burning Brakes
Joined: Feb 2000
Posts: 824
Likes: 2
From: Camden SC
Don't have the manual for the LT1, but am certain they share the same general design. Yours basically doesn't require an adjustment setting.
The computer supplies a 5 volt reference signal from the computer to the TPS. There should be 5 volts at one of the wires going to the TPS. If you have the electrical supplement, you should be able to determine which wire to check. I would get a volt meter, check the reference voltage. You can then check to see if you have a bad connection, bad wiring(supply or ground side), or the computer is not sending out a reference voltage. As a note, the TPS is a 3 wire transducer. One wire supplies a reference voltage, one wire supplies a ground, and the other wire has a varying voltage based on the throttle position.
Let us know. Always curious.
dlmeyers 90 coupe zf6 3 speed shocks
The computer supplies a 5 volt reference signal from the computer to the TPS. There should be 5 volts at one of the wires going to the TPS. If you have the electrical supplement, you should be able to determine which wire to check. I would get a volt meter, check the reference voltage. You can then check to see if you have a bad connection, bad wiring(supply or ground side), or the computer is not sending out a reference voltage. As a note, the TPS is a 3 wire transducer. One wire supplies a reference voltage, one wire supplies a ground, and the other wire has a varying voltage based on the throttle position.
Let us know. Always curious.
dlmeyers 90 coupe zf6 3 speed shocks
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Do you have a stock TB? If so you may need to check the connector for corosion. If you have an ag=fter market TB then you may need to make it adjustable by enlongating the holes, I had to wih my Holley 58mm. I enlongated the holes and set zero throtttle up for .43 VDC and it has worked perfect
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 4,575
Likes: 369
From: Ozark, MO
C5 of the Month 6/13
I'm getting a reading of 4.91 volts for the reference signal at the connector. When the tps is connected and the throttle is opened the reading stays the same. Should there be a change in voltage when the throttle is opened? We took another tps sensor from another vehicle and got the same result. Any ideas?
Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
We took another tps sensor from another vehicle and got the same result. Any ideas?"
Is the TPS actually being rotated by the TB shaft?
How about connecting wires to TPS and moving the switch while it is off the TB?
The TPS is only a reostat , the voltage should increase as the TB is opened up to better than 4V
Is the TPS actually being rotated by the TB shaft?
How about connecting wires to TPS and moving the switch while it is off the TB?
The TPS is only a reostat , the voltage should increase as the TB is opened up to better than 4V
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 4,575
Likes: 369
From: Ozark, MO
C5 of the Month 6/13
Originally Posted by rodj
We took another tps sensor from another vehicle and got the same result. Any ideas?"
Is the TPS actually being rotated by the TB shaft?
How about connecting wires to TPS and moving the switch while it is off the TB?
The TPS is only a reostat , the voltage should increase as the TB is opened up to better than 4V
Is the TPS actually being rotated by the TB shaft?
How about connecting wires to TPS and moving the switch while it is off the TB?
The TPS is only a reostat , the voltage should increase as the TB is opened up to better than 4V
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Le Mans Master
Joined: Aug 2000
Posts: 8,838
Likes: 31
From: Australia
How about a straight resistance check of the TPS?
Put the meter across the correct terminals and see if the Ohms change when it is manually. Will at least prove TPS unit itself is functioning correctly.
but still no reading when the throttle is opened. Are you checking Volts across the correct pins?
The 5V input to earth will not change , only the output to earth Volts
Put the meter across the correct terminals and see if the Ohms change when it is manually. Will at least prove TPS unit itself is functioning correctly.
but still no reading when the throttle is opened. Are you checking Volts across the correct pins?
The 5V input to earth will not change , only the output to earth Volts
Burning Brakes
Joined: Feb 2000
Posts: 824
Likes: 2
From: Camden SC
The supply voltage does not change throughout throttle sweep. It is a constant.
On the MY 90, the throttle position input signal wire is dark blue, check the wiring diagram listed in the electrical supplement for the appropriate model year. It is quite likely you have a dark blue wire(variable voltage-.5 to around 4.5V), a black wire(ground), and a gray wire(4.5 Volts reference voltage-constant).
With the key on, throttle closed, find the wire that has a voltage around .5V DC. This will be the throttle position input signal wire. As the throttle is increased, this voltage should rise and at Wide Open Throttle (WOT), should read around, say, 4.5Volts DC. The Electronic Control Module (ECM) uses this voltage in determining throttle position.
dlmeyers 90 coupe zf6 3 speed shocks
On the MY 90, the throttle position input signal wire is dark blue, check the wiring diagram listed in the electrical supplement for the appropriate model year. It is quite likely you have a dark blue wire(variable voltage-.5 to around 4.5V), a black wire(ground), and a gray wire(4.5 Volts reference voltage-constant).
With the key on, throttle closed, find the wire that has a voltage around .5V DC. This will be the throttle position input signal wire. As the throttle is increased, this voltage should rise and at Wide Open Throttle (WOT), should read around, say, 4.5Volts DC. The Electronic Control Module (ECM) uses this voltage in determining throttle position.
dlmeyers 90 coupe zf6 3 speed shocks
