TEST 2: Verifying Throttle Position Sensor Has 5 Volts And Ground
If you've reached this point, you have tested and confirmed that:
- A TPS diagnostic trouble code (DTC) is lighting up the check engine light.
- The TP sensor's throttle angle voltage signal IS NOT increasing/decreasing as you open/close the throttle plate (TEST 1).
So, in this test section, we're gonna' make sure that it's getting both power and Ground. Both of these are supplied by your Ford Ranger's fuel injection computer and we can easily verify both 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 brown with white stripe (BRN/WHT) wire has 4.5 to 5 Volts with the key on but engine off.
A.) Connect the red multimeter test lead (using the appropriate tool) to the BRN/WHT wire.
B.) Connect the black multimeter test lead to the negative (-) battery terminal.
C.) Your multimeter should read 4.5 to 5 Volts DC.
Verify that the gray with red stripe (GRY/RED) wire has Ground with the key on but engine off.
A.) Connect the black multimeter test lead (using the appropriate tool) to the GRY/RED wire.
B.) Connect the red multimeter test lead to the positive (+) battery terminal.
C.) 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 3.0L Ford Ranger'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 3.0L Ford Ranger as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).
If this info saved the day, buy me a beer!