Diagnosing the 24x crank sensor.

[Azrael]

I tried a crude method of pulling the signal wire from the pcm connector and then started the engine. I didn't notice a difference in idle quality before and after and the SES never lit up.

Is it not critical enough to cause a noticeable difference or have I been driving on a dead sensor for awhile without realising it?

Otherwise, what are the usual failure symptoms?

[mickaz]

with a 24x sensor not working your car would not even start. the ecm pick up the pulse to know where the cylinder is to sync the ignition.

a CPS on the other hand your car would still work, but be a little harder to start and you will loose the SFI, meaning less fuel economy and a little rougher engine...kinda like a 3.1MPFI

[bszopi]

with a 24x sensor not working your car would not even start. the ecm pick up the pulse to know where the cylinder is to sync the ignition.

No. The 24x sensor is only for a higher resolution signal at low RPMs, and doesn't have anything to do with knowing where a cylinder is. The 3x determines cylinder location.

[robertisaar]

a CPS on the other hand your car would still work, but be a little harder to start and you will loose the SFI, meaning less fuel economy and a little rougher engine...kinda like a 3.1MPFI

not quite... if the PCM doesn't detect the cam position, it still operates in SFI based on the last known cam pulse. that's why it can be a rough running engine since there is only a 1 in 6 chance that the injectors fire when they were intended to.

and multiport FI doesn't lose any economy or is a rougher running engine, the 95 MC 3100 running on MPFI in my driveway is living proof. if you can't get an engine to idle with MPFI in place of SFI, learn to tune better.

[mickaz]

i mixed the sensor my mistake, but about the MPFI comment I didn't mean it would not idle, just that it would feel a little rougher... 3.1 are like that and they still idle quite well. and SFI not more fuel efficient then MPFI? that i just don't believe sorry.

[robertisaar]

i have roughly the same pulsewidths required to maintain any speed with a 16149396 running $DF (MPFI) compared to when i was still using the OBD1.5 PCM.

SFI is for emissions, i don't miss it at all.

[MidnightriderZ24]

with the 24x signal not present, the vehicle tends to take a little more cranks to fire up.

[engguy]

If memory serves the manual says, without one or the other sensors, the job is handed off to the one working. It will start and run without the 24X.

[60dgrzbelow0]

No. The 24x sensor is only for a higher resolution signal at low RPMs, and doesn't have anything to do with knowing where a cylinder is. The 3x determines cylinder location.

As usual... "Brad the Elder" is right on point...

This information is an excerpt from another forum post...but germaine to the complete answer to this question...

"A bad camshaft is not going to cause DTC 36 to be set. All that DTC 36 indicates is that the PCM is not seeing the signal from the 24X high resolution Crank Position Sensor (CKP), hiding behind the front damper. This sensor is active from idle to 2000 RPM. Assuming you replaced the proper sensor, you need to check all the wiring and connectors between the sensor and PCM. If the PCM does not see the 24X signal it defaults to the 3X low res CKP. The engine will run OK withut the 24X sensor, but will be harder to start, and may idle a little rough. If you suspect misfires, then you need to look a something else besides the 24X sensor. DCT 36 does not light the MIL lite, so if the lite is lit you need to look for some other DCT. Check the fuel system, fuel pressure and injectors. Check compression "by the book". A cylinder with poor compression will misfire or otherwise cause rough running."

Look for Brad's diagram for how these sensors are all interconnected to the PCM in this prior post link on the subject...

http://60degreev6.com/forum/showthread.php/44878-3400-24x-crank-sensor-ignition-coils-question?highlight=24x+crank+sensor

[Azrael]

Good info. Nothing wrong with my sensor then as my engine starts and idles fine. I was mostly curious as how to know it's had enough and needs replacing.

[3400-95-Modified]

Only time I've ever noticed one to have to be replaced is when my car started developing an idle skip, and also a low RPM cruise skip. You would hear it miss a few times here and there, and if I ran it with the 24x sensor disconnected it went away. Replaced the sensor and all was well.