Took the car for inspection, car was 100% fine. Got inspected, picked it up and started right up. Went home, washed it off cause it was filthy and next time I tried to start it, bam, wouldn't start and got crank position sensor CEL. After a few tries starting it, it got it's head on straight and fired up (weird) and then the rest of the day no problems, drove it around a few places without issue. Brings me to today, fired right up this morning, turned the car off so wasn't idling for 15min waiting to drop the kids at school. Went to start it again and boom, crank no start until I unplugged the sensor, plugged it back in and it fired right up however still had a CEL. This is odd behavior and the only thing I can say that the battery is on it's last good leg but I don't expect that to be the problem because it doesn't change when the car is on a charger or with a charge pack. Just a stock sensor on it's way out?

Can crank position sensor be logged? Assuming not

Do you have any of these symptoms besides #3?
1. Clutch weirdness, improper pedal pressure, strange disengage and engage points
2. Ticking or strange noise from the pulley side of the engine when clutch is depressed.
3. Crank Angle Sensor errors ( check engine light )
4. Difficulty shifting
5. RPMS decreasing significantly when clutch pedal is depressed.
6. Clutch does not return or "sticks" to the floor after being depressed.
7. Clutch does not return or “sticks” to the floor during left hand turns

nice97civic said:

Can crank position sensor be logged? Assuming not

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I believe the RPM is from the crank position sensor. I'd bet you're logging that already.

dwb said:

Do you have any of these symptoms besides #3?
1. Clutch weirdness, improper pedal pressure, strange disengage and engage points
2. Ticking or strange noise from the pulley side of the engine when clutch is depressed.
3. Crank Angle Sensor errors ( check engine light )
4. Difficulty shifting
5. RPMS decreasing significantly when clutch pedal is depressed.
6. Clutch does not return or "sticks" to the floor after being depressed.
7. Clutch does not return or “sticks” to the floor during left hand turns

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Negative to all 7. Just for fun the cel turned itself off while driving it earlier tonight.

Sike, it is acting up again. Guess the sensor is just dead. Great, thats a fun one to replace

Let hope it's not cracked or that the crank plate isn't bent.

No reason for it to be. Car sits most of the year, has 81k on it.

The saga continues. Just went back to the car. Started right up first try with jump pack. No CEL. Why do these cars treat us this way sometimes

Could the problem be in the connector itself? Perhaps some pins not being locked in place when you push the connector together (unplug connector and push every pin to check). Or a connector wire has an intermittent connection issue (wiggle wires around connector while engine is running to see effect).

I’ve unplugged and replugged so many times. Doesn’t seem to make a damn but of difference. I’ll wiggle the wires while it’s running to see but if that were a possibility I’d expect a CEL to pop up more frequently while driving. Still no cel.

The absolute only thing I can think is that somehow it’s related to the battery. Battery is probably due for a replacement and possibly when battery voltage drops, the sensor stops picking up a signal? I’m at a loss. Doesn’t seem to be any other pattern.

Well when running the alt should keep the voltage up unless it's not working. Monitor the voltage at the battery while running to check if alt is putting out and also immediately after it quits.

You might check the voltages on the crank sensor to make sure they are normal.
Red wire is +12v (up to 15v when alt is running).
Black is ground (0v).
Blue-white is signal (it's a pulse when running so meter, on DC, will measure the average): 1.5-2.5v during idle, 0.4-4.0v while cranking.

Well I may have been looking in the wrong spot the entire time . CEL just popped on this morning and after a few minutes of idling it shut off and then wouldn't start. I might just be an idiot.

Can you get a log of it failing and post it?

steve said:

I believe the RPM is from the crank position sensor. I'd bet you're logging that already.

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Revs are from the PTU. once that goes funny they revs drop to half.

best bet is to replace it as a first known cause as they do go bad and get old and the signal fails like ABS sensors do. They work the same way.

Once you checked that then check the PTU connector as that can also vibrate loose and cause no starts and rev issues. mine now has a cable tie on it to hold it onto the connector better

See post #12, I think when I glanced at it the first time I just misread the DTC. Looks like it's a CAM sensor, NOT A CRANK sensor.

nice97civic said:

See post #12, I think when I glanced at it the first time I just misread the DTC. Looks like it's a CAM sensor, NOT A CRANK sensor.

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I jumped straight in after reading your first post. my bad.

hopefully is just the CAS sensor and should be good. least it is easier to swap out for you

nice97civic said:

See post #12, I think when I glanced at it the first time I just misread the DTC. Looks like it's a CAM sensor, NOT A CRANK sensor.

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Aren't they the same thing? 1g has a cam angle sensor and 2g has crank angle sensor.

dwb said:

Aren't they the same thing? 1g has a cam angle sensor and 2g has crank angle sensor.

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No. 2G has Crank and Cam so they talk to each other better and knows what phase it is in. 1G was an all in one and is why they fail and are not as accurate. Most modern systems have crank and cam to be much more accurate and more so now things like VVTI and Variable timing comes into play

FIBA M - EC17PSE said:

Revs are from the PTU. once that goes funny they revs drop to half.

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I don't think so but I'm getting old and forgetful. What I remember is that the Tach signal is from the PTU but the ECU's RPM is from the crank sensor for reasons you somewhat mention. The PTU signal would be subject to changes in ignition timing and the Crank Sensor is about as accurate as you can get WRT RPMs.

steve said:

I don't think so but I'm getting old and forgetful. What I remember is that the Tach signal is from the PTU but the ECU's RPM is from the crank sensor for reasons you somewhat mention. The PTU signal would be subject to changes in ignition timing and the Crank Sensor is about as accurate as you can get WRT RPMs.

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you maybe right on that. I would have to go back and check my logs when my PTU connector jumped off. I know the dash halfed and I am pretty sure the ECU log showed the same. I will need to check this out later on and maybe post it up to go through and see.

nice97civic said:

Well I may have been looking in the wrong spot the entire time . CEL just popped on this morning and after a few minutes of idling it shut off and then wouldn't start. I might just be an idiot.

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So after it died in the driveway while idling, I tried starting a few times. No luck. Unplugged the CAS a few times and tried again, nothing. Put the trickle charger on it, started immediately. I really am at a loss here. FWIW I have a new sensor on the way but this is seeming so random.

Just thinking outside the box now for a weird case so bare with me. Could you have something nothing to do with CAS/CPS? Like a partially leaking FPR (fuel pressure regular) for example? So it dies and then by the time you unplug/plug in something, enough fuel has moved back into the rail on its own to start it? But later since the fuel pressure is not enough (due to leaky FPR) it may die randomly again?

Normally I'd go down that rabbit hole with you but fuel pressure is steady and holds even when the car is off and trails off as the car cools down like normal. If I weren't getting a random CEL as well I would be more inclined to look elsewhere. I don't know how susceptible to failing these are but I can imagine after ~30yrs, a new CAS isn't out of the realm of necessity.

If it's a battery issue it would show up in a log. You want to check how low the battery voltage dips while cranking.
While you're at it cleaning and tightening the terminals isn't a bad idea.

Terminals are tidy. If its a battery issue, then getting a CEL while driving and dying at idle wouldn't be a thing would it? Am I thinking about this incorrectly?