Testing the throttle position sensor (TPS) on your 1996-1997 3.0L Dodge Caravan or 3.0L Grand Caravan (3.0L Plymouth Voyager or 3.0L Grand Voyager) can be easily and accurately done with a multimeter.
In this tutorial, I'll explain the whole test procedure in a step-by-step way.
The contents of this tutorial at a glance:
- Symptoms Of A Bad Throttle Position Sensor.
- TEST 1: Testing The Throttle Position Sensor Voltage Signal.
- TEST 2: Verifying Throttle Position Sensor Has Power.
- TEST 3: Verifying Throttle Position Sensor Has Ground.
- Where To Buy Your Throttle Position Sensor And Save.
- More 3.0L Chrysler Diagnostic Tutorials.
NOTE: The illustrations in this tutorial apply only to 4 specific Dodge/Plymouth mini-vans equipped with the 3.0L V6 engine. To see if this tutorial applies to your specific mini-van, see the Applies To: box in the right column.
The following tutorials may be of help:
- How To Test The Throttle Position Sensor (1991-1995 3.0L Chrysler) (at: troubleshootmyvehicle.com).
- How To Test The TP Sensor (1998-2000 3.0L Chrysler).
Symptoms Of A Bad Throttle Position Sensor
As you're already aware, the accelerator pedal is connected to the throttle plate via an accelerator cable. So, as you step on/off the accelerator pedal, the throttle plate opens/closes. It's the throttle position sensor's job to inform your mini-van's PCM of the throttle angle.
The PCM then uses this throttle plate angle information to: advance/retard ignition timing, calculate transmission shift points, and inject more fuel (among a host of things).
So, having a bad throttle position sensor will cause quite a bit of havoc on your mini-van's engine management system. You'll see one or more of the following symptoms:
- A TPS diagnostic trouble code (DTC) stored in the PCM's memory:
- P0121: Throttle Position (TP) Circuit Performance Problem.
- P0122: Throttle Position (TP) Circuit Low Input.
- P0123: Throttle Position (TP) Circuit High Input.
- Your 3.0L Caravan (Grand Caravan, Voyager, Grand Voyager) fails the smog check (state mandated emissions test).
- Bad gas mileage.
- Hard start and/or extended cranking time (after shut off).
- Black smoke coming out of the tailpipe.
- Hesitation when accelerating your vehicle down the road.
Thankfully, the TPS can be tested without a scan tool and in the next section we'll start with the very first test.
TEST 1: Testing The Throttle Position Sensor Voltage Signal
In a good and working TPS... the voltage signal it produces increases as the throttle plate opens and reaches its wide open throttle position. This voltage then decreases back to its original base value as the throttle plate closes.
You and I can confirm that this is actually happening by tapping into the ORG/DK BLU wire with a multimeter. The ORG/DK BLU wire connects to TPS pin #2 (see illustration above).
NOTE: The throttle position sensor has to remain connected to its connector for this test to work (this is where a wire piercing probe comes in handy to get to the signal inside the wire. To see what one looks like, click here: Wire Piercing Probe Tool.)
OK, let's start:
Place your multimeter in Volts DC mode and with the RED multimeter lead probe the ORG/DK BLU of the sensor's connector.
The ORG/DK BLU is the TPS signal wire.
Ground the BLACK multimeter test lead on the battery negative terminal. Have you helper turn the Key On, but don't start the engine (this will power up the TP sensor).
Your multimeter should report a voltage between .2 to .9 Volts DC. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
Now, slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.
As the throttle opens, the voltage numbers will increase. This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
Now, slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.
OK, now you'll need someone to help you lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle and observe the multimeter.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.
Repeat step 7 several times to make sure of your multimeter test results.
Let's take a look at your test results:
CASE 1: The throttle angle voltage increased and decreased as you opened and closed the throttle plate. This confirms that your 3.0L equipped mini-van's TP sensor is OK and not defective.
CASE 2: The throttle angle voltage DID NOT increase (and/or decrease) as you opened and closed the throttle plate. This tells you that the TPS is bad and causing the TPS trouble code lighting up the check engine light (CEL) on your 3.0L equipped mini-van.
Before you run out and buy it... I'm gonna' suggest that you do two more tests. One is to check that the TPS is getting power. The other is to check that it's ground. To check that the TPS is getting power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.
CASE 3: Multimeter DID NOT register any voltage, this test result doesn't condemn the TP sensor as BAD just yet. Why? Because...
... the TP sensor may be missing either power or ground. So the next step is to check that the TP sensor is getting power, go to TEST 2: Verifying Throttle Position Sensor Has Power.