Crank sensor signal voltage

Hi, I am working on 2012 Ford F550, with a 6.7l powerstroke diesel.

My issue is I cannot figure out why I have 2.38 volts on the signal wire of the crank sensor. I cannot create a square wave either from the crank timing ring while cranking or just from putting the sensor in the air and waving a piece of metal in front of it.

As far as I can find this is supposed to be a drop down type hall effect sensor. When I disconnect the sensor I get ~4.93 volts on the signal wire, and it has good ground and a good 5 volt reference. But when I plug in the sensor or even a second sensor I get 2.38 volts.

The original issue was the truck had code p0335, and I found the pigtail at the crank sensor was rubbing on the transmission housing and shorted all 3 wires to the crank sensor, I put in a new sensor repaired the pigtail but cannot get the code to go away and can't even test to see why its not working because of the odd voltage on the signal wire. All voltages have been tested at both pcm, and at the connector of the sensor.

I cannot figure out if I am doing something wrong or if this is perhaps a variable hall effect sensor of some kind, and my test procedure should be different. Please help, thank you

With a test light to ground, CKP sensor unplugged, scope on signal at PCM, and watching the rpm PID on the scanner.

Repeatedly tap the signal wire, can you make a square wave, and does the PCM produce an rpm?

If yes, sensor or reluctor issue, are you using OE replacements?

It's not uncommon to have 2 "new' sensors Dead right out of the box.

Thank you for the response, however while using a test light or scanner or lab scope I get voltage at signal wire. I cannot make a square wave or get rpm from scanner.

As mentioned in my first post, I get a constant 2.38 volts on the signal wire with the sensor connected. No on or off just constant 2.38 volts. But when the sensor is unplugged I get 4.93 volts.

Does this seem correct or is it possible the signal wire is still shorted, or am I testing this incorrectly?

Thank you

I seem to have misunderstood your reply. I will test what you ask, thank you

After testing, I can produce a square wave with the sensor disconnected, and putting the signal wire to ground.

These are both oem sensors from the ford dealership, I am having trouble understanding why a hall effect sensor could produce less voltage other than zero when connected? I mean its a simple on and off switch transistor. Perhaps someone can chime in.

I will update after getting another sensor

Thank you

Do you get rpm on the scan tool?

For shits and giggles, is the 5 v ref dropping out to 2.38 as well as the signal when you plug it in?

The ground will light up a 0.5amp bulb?

I can't help but think there is some unwanted resistance on the ground.

With the sensor connected the 5 volts is good. I have not tried to see rpm with the scanner yet by tapping signal to ground but I will. I have a aftermarket sensor coming just to see if there is a difference.

BTW I have actually already replaced the pcm because of a completely separate issue with the reductant system, both the old and new pcm show the same results, the sensor return (ground) is through the pcm for the crank sensor. I've been thinking of bypassing the harness and wiring straight to the crank sensor to test this further. But ill wait till I get the new sensor just to see if that is the issue.

Thanks for your help.

Appears your wiring integrity is good on the 5v ref and sig however you only mention a good ground. What actual voltage do you have on the ground?

The most I've recorded is 0.1 volts.

Also I just installed a third sensor, same issue. I bypassed the harness completely giving battery ground to the sensor and separate wires for both 5 volts, and signal. Same exact thing.

4.93 volts sensor unplugged and 2.38 volts plugged in, but no change with metal in front of sensor

Ford has keep alive memory. Have you cleared that?

VegasJAK wrote:

Ford has keep alive memory. Have you cleared that?

So it could turn out a keep dead memory :silly:

Technically no but I did change the entire pcm. But ill look into that. Wouldn't that clear when clearing dtc's?

No, KAM remains. On Ford, the KAM holds all learned values. When you clear a DTC it's only clearing that code not the learned value. If you disconnected the battery, this is one way to reset the KAM. Resetting the KAM may or may not work, just trying to think outside the box for alternatives.

Thanks for that. I cleared the KAM, but no change.

Magnetized wheel? Even bypassing the harness produced the same results?

So, new sensor, pcm, and harness didn't fix it. When you are plugging it in and seeing the voltage drop, is the sensor installed or off the vehicle, or does it not matter?

So it's a permanent code then. It won't clear until you resolve the problem. If those crank wires were exposed for a while, corrosion could run deep within the wires. Might want to do resistance check on those wires and maybe bypass them all together.

That is one thing I have not tried is using a magnetized wheel.

But no, whether I try to test the sensor in its slot or hanging in the air it does not matter

Interestingly Ford tech notes say not to use a magnetic near the sensor or damage could occur. Screw that I've got 3 sensors now I'm going to try it.

I did try to bypass them all the way to the pcm. No change

Tutti57 was referring to this:

The Magnetized Reluctor, but you need a Guass Meter to detect it; Here's Bernie fixing one, what a chore!



But it is usually caused from ground cables being ran incorrectly and the electron return path has been changed.

A test light will pull the signal down to ~0 ish, but any sensor you put in only 2.38V. Bizarre.

When you bypassed the entire harness were you still using the vehicles PCM concector backprobed?

Did you drag test the PCM Coneectors?

This is a good one for sure.