How To Test The Crank Sensor (Ford 3.0L, 3.8L)

The clearest indication that the crank sensor on your Ford 3.0L or 3.8L car, mini-van or pick up has failed, is a cranks but does not start condition.

Since so many things can cause a no-start problem, it's always a good idea to tests the components suspected of causing the no-start first before replacing them. In this article, I'll show you how to test the crank sensor with a multimeter in Volts AC mode.

Important Tips And Suggestions

TIP 1: The crank sensor is located right behind the crankshaft pulley, since the crank sensor's reluctor wheel is behind (and part of) the crank pulley.

TIP 2: Since this is an On Car test of the crank sensor, you'll need to crank the engine to test it. For this reason, the battery on your Ford vehicle must be fully charged.

TIP 3: You'll need to jack up the vehicle to gain access to the crank sensor. Use a jack stand to hold the car up in the air. Do not trust the jack! Wear safety glasses to protect your eyes from falling debris. Think safety all of the time (your safety is your responsibility)

TIP 4: When the crank sensor goes bad, you'll get a no-spark no-start condition. So, if you're getting spark, even if in just one cylinder, the crank sensor is good and this test will not help you.

Symptoms Of A Bad Ford Crank Sensor

When the crank sensor goes bad on your Ford 3.0L or 3.8L vehicle, the very first symptoms you'll see is a 'no-start no-spark' condition affecting your car.

Here are some more specific symptoms of a bad crank sensor:

1. Your 3.0L or 3.8L car (pick up, mini-van) will 'crank but not start'.
   • So if your car starts, the crank sensor is working.
2. The PCM (Powertrain Control Module= Fuel Injection Computer) will not pulse any of the 6 fuel injectors.
   • You can easily verify this with a Noid light test. If the Noid light flashes ON and OFF, the crank sensor is OK.
3. No spark coming out of any of the 6 spark plug wires.
   • You can check this with a simple spark test and if you've got spark, the crank sensor is OK and doing its job.
4. The coil pack will not get any switching signals from the PCM (Powertrain Control Module = Fuel Injection Computer).
5. Sometimes (but usually never), the PCM will set a diagnostic trouble code to indicate a problem with the crank sensor:
   • P0320: Erratic Profile Ignition Pickup (PIP) pulses.

How Does The Crank Sensor Work

The crank sensor on your 3.0L, 3.8L Ford car or mini-van is a two wire reluctor type. Ford labels this sensor as a magnetic transducer type.

In plain English, this means that this type of crank sensor creates its own voltage signal without an external power source. Here are some more specifics:

1. As the engine starts to crank, the trigger wheel mounted on behind the front crankshaft pulley starts to rotate.
   • The trigger wheel has a total of 35 teeth spaced 10 degrees apart, with one empty space for a missing tooth.
2. As this trigger wheel's teeth pass under the crank sensor, they induce the crank sensor to create an A/C voltage that the PCM uses to activate the ignition coil pack and the fuel injectors.
3. The primary indicator of the crankshaft speed and piston Position is the missing teeth on the trigger wheel.
4. The PCM then uses this info to activate:
   • The ignition coil pack.
   • Fuel injectors.
   • The PCM also uses the crank sensor signal to activate the tachometer on your instrument cluster (if equipped).

Bottom line is that if the crank sensor fails in your Ford vehicle, it's not going to start due to a lack of spark and fuel.