How To Test a Ford Focus TPS Sensor

The Focus TPS Sensor in your Ford is responsible for measuring the position of your throttle blade. As you depress your Focus accelerator pedal, your throttle body opens. The throttle position sensor is mounted opposite of the throttle blade, and this sensor reads the position and relays it to your engine computer.

Because your Focus TPS Sensor is basically a potentiometer that’s mounted to measure how far your throttle has opened. When this sensor goes bad, your engine computer will be operating blind and your 2.0 liter ZETEC engine performance will suffer.

Today I’ll be showing you how to test the Focus TPS Sensor in a 2004 Ford with a 2.0 liter ZETEC engine in it. The throttle sensor in your Focus is a three pin unit, and mounted by way of two screws to your throttle body. Replacing this sensor is easy to do, but you’ll need a digital multimeter to test as well as install and calibrate your Focus TPS Sensor.

Problems with your Focus TPS Sensor can lead to a few issues, mostly related to your idle. Some of these issues can also be dangerous, but one of the first indicators that something is wrong is your OBDII check engine code.

When you see the check engine light turn on in your Ford Focus instrument cluster, you’ll need an OBDII scan tool to retrieve the code.

Symptoms of a bad Focus TPS Sensor

Because your Ford engine computer relies on this signal to operate your engine, the check engine light being ON isn’t the only issue. Some of these other common symptoms can range check out a few below :

• Poor gas mileage
• Hard time starting your Ford Focus
• Inconsistent idle
• Hesistation during acceleration

Some of the OBDII codes you’ll usually see when your Focus TPS Sensor goes bad can include :

• Code P0120: Throttle Position (TP) Circuit Performance Problem
• Code P0123: Throttle Position (TP) Circuit High Input
• Code P0122: Throttle Position (TP) Circuit Low Input

Testing your Focus TPS Sensor for Power

Before you begin you’ll need to remove the intake piping that leads to your throttle body. You won’t need to start the engine but your ignition key should be turned to the “ON” position. This enables your Ford Focus 2.0 liter ZETEC sensors to receive power and ground from the PCM, which you will be testing first.

The first wire you’ll be checking is the wire that leads to PIN C, which should be the switched power signal. Disconnect your Focus TPS Sensor and test this wire first for power. You should have around 5 volts of DC power here with the key turned to the “ON” position.

If you have power at this wire, the next one to check is PIN A. You have probably put the black lead of your multimeter to the negative terminal of your battery, and probing the front of PIN C with your red lead. Now reverse the leads and test the WIRING harness side of PIN A for a sensor ground.

Once you’ve confirmed power and ground signals, this means that your Focus TPS Sensor is being powered up. The last leg of this How To Guide is testing the Focus throttle signal from your three pin TPS sensor.

Testing your Focus TPS Sensor Signal

Now you’ll need to reconnect the throttle position sensor, and you’ll need to pierce the middle wire with your multimeter lead. You still won’t need to start your engine, but the ignition key needs to remain in the “ON” position.

At this position probe the middle wire by piercing it with your red multimeter lead. Now you are going to be measuring the voltage signal being sent by your Focus TPS Sensor. At the closed position this sensor should read between .8-1.0 of TPS signal. This is the voltage being sent to your Ford computer with the throttle plate in the closed or default position.

Now you can either have a friend jump into the Focus and push your gas pedal all the way down, or open it by hand. Because this 2004 Ford Focus doesn’t use a Drive By Wire system, simply reach down to open your throttle body. Because the throttle body is facing upwards, towards the hood of your Focus you should be able to open the throttle completely.

At the Wide Open Throttle position your Focus TPS Sensor should read between 4.5 and 5.0 volts of DC signal. Now slowly close and open the throttle, while reading the signal wire. The voltage should slowly rise and scale back evenly, without gaps or spikes in the signal. If your Focus TPS Sensor doesn’t respond accordingly, you will need a replacement throttle sensor.

Have any questions about this Focus TPS Sensor guide? Leave us a comment below and let us know!