TEST 2: Verifying Throttle Position Sensor Has Power
The TPS needs power and Ground to produce a throttle plate angle voltage signal. So, in this test section we'll use our multimeter to make sure it's getting power (we'll check for Ground in TEST 3).
As you're probably aware, this power is in the form of 5 Volts DC and is supplied by your mini-van's PCM.
The VIO/WHT wire, of the TPS connector, is the one that feeds the sensor with these 5 Volts. The VIO/WHT wire is the one that connects to TPS pin #1 (see illustration above).
OK, here are the test steps:
Place your multimeter's dial in Volts DC mode and turn the key on but don't start the engine.
This will power up the TP sensor's connector.
Check the TPS connector VIO/WHT wire with the red multimeter test lead.
IMPORTANT It's not a good idea to probe the front of the TPS connector. Probing the metal terminal of the TPS connector could damage it and require that you replace the connector. Use a back probe or a wire piercing probe instead of probing the front of the connector.
Connect the black multimeter test lead to a good and clean Ground point on the engine or directly on the negative (-) battery terminal.
When you've set up the test, have a helper turn the Key On Engine Off (KOEO).
Your multimeter should display 4.5 to 5 Volts on its screen.
Let's interpret your test result:
CASE 1: The VIO/WHT wire of the TPS connector, has 4.5 to 5 Volts. This means that the throttle position sensor (TPS) is getting power from your 3.0L equipped mini-van's fuel injection computer.
The next and last test, is to make sure that the throttle position sensor is getting Ground (from the PCM too). For this test, go to: TEST 3: Verifying Throttle Position Sensor Has Ground.
CASE 2: The VIO/WHT of the TPS connector, DOES NOT have 4.5 to 5 Volts. Double check all of your connections and repeat the test.
If your multimeter still doesn't register the 4.5 to 5 Volts DC, then you have just confirmed that the reason the TPS is not working is due to a lack of power (5 Volts). Although it's beyond the scope of this tutorial, your next step is to diagnose and restore these missing 5 Volts.
TEST 3: Verifying Throttle Position Sensor Has Ground
In this last test section, we're gonna' make sure that the BLK/LT BLU is feeding the TPS with Ground.
We can check this Ground by doing a voltage test with our multimeter in Volts DC mode.
In case you're wondering, the BLK/LT BLUwire is the one that connects to TPS pin #3 (see illustration above).
IMPORTANT: Ground is provided directly by the fuel injection computer. Be careful and don't intentionally or accidentally short this wire (circuit) to battery power or you will fry the fuel injection computer.
OK, here are the test steps:
Set your multimeter to Volts DC mode.
Probe the TPS connector BLK/LT BLU wire. The BLK/LT BLU is the one that feeds the TPS with Ground from the PCM.
It's not a good idea to probe the front of the TPS connector. Probing the metal terminal of the TPS connector could damage it and require that you replace the connector. Use a back probe or a wire piercing probe instead of probing the front of the connector.
Now, with the red multimeter test lead, probe the battery positive (+) terminal.
Turn the key to its ON position but don't start the engine. This will power up the fuel injection computer.
Your multimeter will display 11 to 12 Volts if the BLK/LT BLU wire is feeding the TPS with Ground.
Let's interpret your test results:
CASE 1: The multimeter showed 11 to 12 Volts. This is the correct and expected test result and confirms the TPS is getting Ground.
You can now confidently conclude the TPS is bad because you have confirmed that:
- The TP sensor is not producing an increasing/decreasing throttle angle voltage signal (TEST 1).
- The TP sensor is being fed 5 Volts DC (TEST 2).
- The TP sensor is being fed Ground (TEST 3).
Replacing the TPS should now solve the TPS trouble code (P0121, P0122, or P0123).
CASE 2: The multimeter DID NOT show 11 to 12 Volts. Double check that you're testing the BLK/LT BLU wire and repeat the test.
If your multimeter still indicates that the TPS is not getting Ground, then we can conclude that one of two things are causing this lack of Ground:
- There's an open in the wire between the TP sensor harness connector and the fuel injection computer's harness connector.
- The fuel injection computer has an internal problem (although this is extremely 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 equipped mini-van as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).
More 3.0L Chrysler Diagnostic Tutorials
You can find a complete list of 3.0L Chrysler/Dodge/Plymouth tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test For A Broken Timing Belt (1988-2000 3.0L SOHC Chrysler) (at troubleshootmyvehicle.com).
- How To Replace the Distributor (1988-2000 3.0L Chrysler) (at troubleshootmyvehicle.com).
- How To Test The Throttle Position Sensor (1991-1995 3.0L Chrysler) (at troubleshootmyvehicle.com).
If this info really saved the day, buy me a beer!