P1120 Ford 3.0L – How To Test TPS
The P1120 Ford OBDII Diagnostic Trouble Code is signifying a direct issue with your vehicle’s throttle position sensor (TPS) sending a signal that’s not expected by your Powertrain Control Module (PCM). Your Ford PCM requires this signal so that your engine can run as efficiently as Ford originally intended. This check engine light can cause your Ford to go into limp mode, which will allow you to take your vehicle to an experienced mechanic for diagnosis.
If you have this P1120 Ford DTC trouble code, it means that you have a problem with your TPS.If this problem is severe you will have no throttle response at all meaning the sensor is not communicating with your Ford PCM. Your sensor has either failed or there’s a break in your wiring.
I will be showing you today how to test and service your Ford TPS in a 2003 Ford Taurus SES with the 3.0 liter Ford Duratec engine.
Possible Causes of P1120 Throttle Position Sensor Out Of Range
- Failed throttle position sensor
- Throttle position sensor harness has a short or break
- Throttle position sensor circuit poor electrical connection
- Throttle position sensor not properly calibrated
Where is my TPS and how does it work?
The 3.0 liter Ford Duratec TPS is located on the throttle body, which is connected to the intake tract, mass air flow (MAF) meter and airbox. This sensor is a potentiometer type sensor that’s comprised of 3 ECM circuits. I’ll be showing you how to test each wire as well as how to test your Ford Taurus throttle body on your 3.0 liter Duratec engine for proper operation.
Measuring the deflection of the throttle blade, or how far you are depressing the accelerator is this sensor’s main job. It provides real time values to your PCM, allowing closed loop operation. Because your PCM is expecting a different value from this sensor, it triggers the P1120 OBDII trouble code and can also trigger P0122 as well.
You will need a 10mm socket and wrench, a flathead screwdriver and a multimeter capable of reading voltage and continuity.
How to Remove the Mass Air Flow (MAF)
Remove the 10mm bolt that secures your Ford airbox in place to the driver side fender.
Next unplug your MAF sensor and make sure that you do not lose the inner mass air flow sensor gasket inside the connector during the unplugging process.
Gently grab the plastic connectors circled in orange and remove them from the accordion style intake tract. Use care when removing these as age and heat can make them brittle, do not crack or break these 90 degree plastic vacuum plugs.
Unscrew the two clamps on the intake tract circled in green and compress the tract to remove from the engine bay. You should now see your throttle body and throttle position sensor, with the three pin weatherproof connector.
You are now ready to test your 3.0 liter Duratec throttle position sensor to see what is causing your P1120 OBDII DTC Trouble Code.
How to Test the Ford Throttle Position Sensor Power
Turn the key to the “ON” position but do not start the engine. Put the black lead of your multimeter to the negative terminal of your battery, and check pin 3 or the black wire with white stripe for a switched 5 volt signal.
Now check PIN 1 for the low reference circuit or the ground in your MAF connector.
If you have power and ground at these two wires, your 3.0 liter Duratec engine is powered and should be sending the signal to your PCM. Reconnect your throttle position sensor and backprobe PIN 2 of your 3.0 liter Ford Duratec throttle position connector. This is the signal wire that is either not sending signal or cannot send the right range of signal back to your PCM.
With the key still at the “ON” position but with the engine off, backprobe this pin while depressing on your throttle blade slowly to open it.
The signal reference you should see here will be lower than a volt with the throttle blade closed and near 4.3 to 4.5 volts with the throttle blade open.
If you do not see this signal, or there are odd jumps and spikes in the voltage range your throttle position sensor is bad and must be replaced. The Ford part number for this unit is F5RF-9B989-BA but can also be found under F5RZ-9B98-9B or F5RZ9-B989-BA at substantially lower prices. This part also shares a Mazda part number as this 3.0 liter Duratec was found in many other makes and models from Jaguar’s S-Type and Mazda MPV as well as the Mazda 6.
The Mazda part numbers for the Duratec throttle position sensor are 1F2218851A and AJ0318911A respectively. The P1120 Ford OBDII trouble code also applies if the signal from the TPS is too low, replacing your TPS is recommended if all the tests above check out.
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Thanks for reading!