Crank Position Sensors question...
 

Ok well i know one of them needs to be replaced and for a while i didn't realize our engines had two so now i'm confused as to which one to replace. I know each one has their functions so i'm wondering which one is the one that affects drivability? Is it the cylinder shaped one? That's the one i bought today but after doing some reading i'm not sure if i have the right one. Is the cylinder shaped one the 24x one or the 3x one? Any help is appreciated. I'm bringing it in tomorrow to have the sensor put in but just wanted to be sure i have the right one.

We have only one crank sensor and 2 cam sensors.

The round one goes on the front of the block right behind the power steering pump. I'm pretty sure that's the 24x sensor, the 7x I've never seen. It's up high, by the firewall. Very hard to do without a lift. 3x is the purple wire that comes off the ICM and runs to the PCM

The crank sensor is behind the balancer

cammmm....ahhhhhh. ok. wow....idk how i misread that :-X Thank you sir.

No prob, I did the same thing :eek:

2 crank sensors and one cam sensor....

The 7x (3x) is mounted through the rear of the block to a reluctor wheel on the crank itself. This sensor only provides a signal to the Ignition Control Module, the ICM communicates with the PCM. The 24x sensor is mounted behind the harmonic balancer and provides a higher resolution signal to the PCM. The cam sensor is under the power steering pump and is connected to the PCM. The combination of the 24x and cam sensor are what enable the "SFI" to work. The older MFI engines (before 1994) only had the 7x sensor for everything.

I don't recall if the PCM will have a fail-safe if the 24x sensor fails. If the 7x sensor fails, I'm 99.9% sure it's not going to run.

They all can affect driveability.

Replace 7x and the connector going to it. The wire from the IGM is routed right next to the rear manifold and is exposed to massive amounts of heat. It is a 2 wire lead going from the module to the 7x sensor at the back of the block. The sensor is not like the 24x at all. The 24x utilizes a reluctor wheel on the exterior of the crank inside your balancer. The 7x is a internal one, made of plastic by the way, and also is exposed to insane amounts of heat inside the block. What happens is the two wires will fuse and skew the signal from the sensor and the sensor its self, again being plastic, cracks from the heat and also skews signal causing stalling, idle issues, horrible mileage and so on. Ive seen this more times than I can count including three sensor replacements on my own GA. This issue was first found in minivans with the 3400's. Now, more recently, this problem is becoming more and more common...

...oh almost forgot something really, really important here as well. You do need to have a Tech2 to relearn the sensors. Most mechanics, even the GM guys, don't know this is necessary. My GM mechanics told me it could not be done, its not in the programming... they are dead wrong boys, its in there, done it myself and educated my guys about it as well so now they know to perform the learn whenever they mess with either sensor on a 3400

Well....brought it to the place to get the new sensor put in and the guy said there was no wire connected to it. He said the wire that does connect to it is connected to an external crank trigger (the one in the 3500 swap kit). But idk...we put this all together before and it worked and everything plugged in. IDK why the plug is missing.....i'm really pissed though. Seems like this problem will never end :/ IDK what to do..

no wire connected to what? The external crank trigger is the 7x sensor. The sensor / reluctor in the block on the 3500 is WAY different.

No wire connected to the crank sensor. (cylinder shaped one). The guy couldn't find the wire....idk....i mean i'll check tomorrow but he had it up on a lift/down...so he had better views than i'll have.

Another cylinder shaped one should be installed in the external crank trigger if that's what you have..

Yea i have one like that. Shoot....i hope it's not that one that's bad. Idk what type of sensor that is cause it came with the swap kit. I'll have to get ahold of mike. I thought it was the one that goes in the block. I'm confused cause he said the sensor was unplugged...and idk if the wire that usually commects to the sensor in the block was rerouted to the external one. Ahhh!

Sounds like the sensor behind the crank pulley was left on the front cover and the wire was rerouted to the external sensor.

The external one is the 7x sensor. The 3500 crankshaft doesn't have the right wheel on it to run with the 3400 computer, hence the external. The 24x is the original under the harmonic balancer.

As far as I know, it's the same stock 7x sensor.

I like the way its set on the 3500... not inside getting the snot knocked out of it from heat!!