How To Test a Ford F150 Crank Sensor

How To Test a Ford F150 Crank Sensor

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Your Ford F150 truck uses a variety of sensors and engine components in order to operate. One of the more important happens to be the Ford F150 crank sensor. This sensor is what tells your engine computer what position your crankshaft is in, and how fast it’s spinning. Using this data your Ford truck computer will deliver just the right amount of fuel and ignite your spark plugs at the correct time.

Problems with this F150 crank sensor can make life hard for you and your truck. If your F150 won’t start or takes a long time to start, this can be an early warning sign of your crank sensor going bad. Another obvious sign is the check engine light turning on in your F150 instrument cluster.

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If your F150 won’t start and your check engine light is on, the first order of business is a OBDII scan tool. Using this tool you can easily connect to your On Board Diagnostic computer, and retrieve your alphanumeric code.

Today I’ll be showing you how to test the F150 crank sensor in a 2008 truck with the 5.4 liter engine in it. Unlike other crank angle sensors, the one in your F150 truck is a variable reluctance sensor it’s very easy to test. Without a true power and ground wire in a traditional hall effect or optical crank sensor, you’ll need a digital multimeter to measure resistance.

Symptoms of a bad F150 crank sensor

Because this sensor is what your Ford Powertrain Control Module references to operate the engine, F150 crank sensor failure should never be taken lightly. If you are driving at speed and your PCM doesn’t receive a signal, the engine will shut off unexpectedly. Automatic transmission equipped F150 truck owners will have a serious problem, because this means the truck will be moving without power brakes or power steering.

If you have a check engine code for your F150 crank sensor, or think your sensor is bad do not drive the truck. There are several problems that will arise from a bad crank angle sensor, here’s just a few below.

  • F150 Won’t start
  • Truck is Hard to Start
  • Engine shuts off Intermittently
  • Check Engine Light ON

A weak truck battery can also trigger this check engine light falsely. This can happen because your Ford F150 crank sensor isn’t powered. Your truck computer can misdiagnose a bad crank sensor related to this weak voltage.

How does the F150 Crank Sensor work?

When you go to start your Ford truck, the crank sensor plays a vital role. When your starter turns the engine, the crank rotates and the variable reluctance sensor picks up this signal. The Ford F150 crank sensor sends this signal to the ignition control module, which generates a Profile Ignition Pickup signal.

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This signal is used to fire your fuel injectors and start your engine. If the your F150 won’t start then it’s a good idea to use a noid light to check your injectors first. Failure for your fuel injectors to fire means that it’s a good chance your crank angle sensor is bad.

How To Test Your F150 crank sensor

Before you begin it’s a good idea to remove your spark plugs. This allows your 5.4 liter engine to rotate easier, and to test the crank sensor without starting the F150 engine. There’s two ways to go about the testing of your F150 crank sensor. The easiest is to disconnect the crank sensor harness from the unit and pierce the wires in the harness.

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Now connect the crank angle sensor and put the multimeter leads to the wires inside of the harness.

You don’t need to worry about the orientation of the wiring, or the polarity. Turn the multimeter to the read DC voltage and you’ll b reading the voltage being transmitted by the sensor.

 

Now turn the ignition key to the “ON” position. Manually rotate your engine by using a crank tool or half inch drive. As you spin your 5.4 engine manually, you’ll see that your F150 crank sensor should be fluctuating voltage

If it’s working properly this crank sensor should transmit voltages that fluctuate between .5 Volts AC to 1 Volt. When this sensor is not responding make sure that your key is turned to the “ON” position and that your carnk angle sensor connected. Ensure that the wires are properly pierced and your multimeter leads are firmly seated to get a real reading.

When your Ford F150 crank angle sensor doesn’t respond or react with the right voltage ranges, it means the sensor has died. You will need a replacement crank sensor to restore your truck back to operation. Have any questions about this F150 crank sensor tutorial? Leave us a comment below and let us know!

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