TEST 2: Verifying Throttle Position Sensor Has 5 Volts And Ground
In this section, we're gonna' make sure that your 2.0L Mazda 626's throttle position sensor is getting power and ground. So, if you have reached this point, you have already confirmed that:
- A TPS diagnostic trouble code (DTC) is lighting up the check engine light.
- The TP sensor did not pass TEST 1 because it's voltage signal IS NOT increasing/decreasing as you open/close the throttle plate.
Both of power (5 Volts) and ground are supplied to the TPS by your 2.0L Mazda 626's fuel injection computer. We can easily verify that both of these are being fed to the TPS with a simple multimeter voltage test.
IMPORTANT: The PCM is the one that feeds this ground to the throttle position sensor (TPS). Be careful and don't short this wire to battery voltage or you'll fry the PCM.
With your multimeter in Volts DC mode, this is what you need to do:
Verify that the wire that connects to terminal #3 of the connector has 4.5 to 5 Volts with the key on but engine off.
Connect the red multimeter test lead (using the appropriate tool) to the wire that connects to terminal #3. Connect the black multimeter test lead to the negative (-) battery terminal.
Your multimeter should read 4.5 to 5 Volts DC.
Verify that the wire that connects to terminal #1 of the connector has ground with the key on but engine off.
Connect the black multimeter test lead (using the appropriate tool) to the wire that connects to terminal #1 of the TPS connector. Connect the red multimeter test lead to the positive (+) battery terminal.
Your multimeter should read 10 to 12 Volts DC.
Let's take a look at what your test results mean:
CASE 1: The TP sensor is being fed power and ground. This is the correct and expected test result.
You can conclude that your 2.0L Mazda 626's TPS is bad only if all tests have confirmed that:
- The TP sensor IS NOT providing a varying voltage signal when manually opening/closing the throttle plate.
- The TP sensor is being fed 5 Volts DC.
- The TP sensor is being fed ground.
CASE 2: The TP sensor IS NOT being fed power or ground. Double check your connections and make sure that you're testing the correct wires. If your multimeter still does not show power and/or ground...
...then you can conclude that there's an open in the wiring between the TP sensor harness connector and the PCM's harness connector. In the extreme of cases, the PCM has an internal problem (although this is very rare).
Although testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your 2.0L Mazda 626 as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).
Where To Buy The TPS And Save
The following links will help you to comparison shop for a new 2.0L Mazda 626 TPS. I think they'll save you a few bucks:
Not sure if the above TPS fits your particular 2.0L Mazda 626? Don't worry, once you get to the site they'll make it fits by asking you the specifics of your particular Ford vehicle. If it doesn't fit, they'll find you the right one.
More 2.0L Mazda Tutorials
If this tutorial was helpful, check out the other Mazda 2.0L tutorials that I've written. You can find them all here: Mazda 2.0L Index of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test For A Blown Head Gasket (2.0L Mazda 626).
- How To Test The MAF Sensor (1996-1997 2.0L Mazda 626).
- How To Test Engine Compression (2.0L Mazda 626).
- How To Test The Fuel Injectors (1993-1999 2.0L Mazda 626).
- How To Test The Fuel Pump (1994-1999 2.0L Mazda 626).