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Old 06-02-2006, 09:14 PM   #1
Gnomonic
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Testing Throttle Position Sensor

Could anybody let me know if I'm diagnosing a bad TPS properly.

Engine off, ignition off.

Remove TPS connector from TPS.

Place one lead of Multimeter (set on 20 Ohms) in center terminal of TPS and the other lead in one of the two outside terminals.

Ohms should be roughly 1.2 when throttle is closed.
As throttle is opened Ohms rise consistently to approx 5.3.
Release the throttle and it decreases back to 1.2.

Do the same thing except put the second lead in the other outside terminal, and the results should be the same.

Is that the correct procedure?

On mine, one side works fine...the other side has an Ohm reading that jumps all over the place, mainly between 10 and 20 Ohms. Occasionally it will hover around 15 Ohms and when the throttle is opened is DECREASES to about 10 Ohms.

Is the right? Does one terminal act differently than the other?

Thanks in advance.
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Old 06-03-2006, 02:54 AM   #2
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Re: Testing Throttle Position Sensor

it might help you to know that the schematic of the stuff in the tps looks something like this:

//////////////////////////////////
| ^ |
V-| |V1+ |V2+

where V- is the supply voltage (usually 5v.), V1+ is the voltage derived from the position of the wiper (the up pointing arrow; it is free to move across the resistor coil), and V2+ is of a constant voltage that the ecu uses to determine if the resistor coil that the wiper rides on has a short or an open circuit (V2+ should always be constant). if the wiper is hitting dead spots try spraying the inside of the tps with electrical contact cleaner and actuating the wiper a few times to clean the coil. if the first terminal that you use as your testing point is the wiper then the other two terminals should act oppisite of eachother.

it seems that the posting system ignored the spaces in the drawing, so imagine v- being at one side, v2+ on the other and v1+ being free to move across the coil (all of the forward slashes).
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Old 06-03-2006, 09:08 AM   #3
CraigFL
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Re: Testing Throttle Position Sensor

The other thing is that many of these get tested when you run the OBD test procedure. At the start of my test, it is required to push the accelerator to the floor for a moment and the computer checks it.
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