Engine/Transmission (1994 - 1998) crankshaft position sensor

[Loghead]

I replaced mine about a year ago, and now I'm starting to have the same problems again, usually when the engine is cold and the weather is wet.
Once warmed it seems to run alright.

How long should a new sensor last?

oops! I almost forgot...

truck is a '97 2500 4x4 AT

 

[robbiesworld]

If you are speaking of the ESS Engine Speed Sensor Mine lasted 325K miles. I would think if it is aftermarket it could be junk and not last very long. I'm still confused how a magnet goes bad anyways!



What problems are you having?

No Tach?

No overdrive?

No TC lockup?

Not Charging?

 

[Loghead]

I believe it was the Niehoff brand, which I've always found to be decent, but you never know.
This sensor is mounted at about the ten o'clock position (when facing the front of the engine) near the harmonic balancer.

The symptoms?
The one I notice most readily is the inexplicable down-shifting, which is one thing it would do with the old sensor.
Probably the tach and speedo are out to lunch as well, but so far it happens very intermittently and very briefly, so I haven't had a chance to notice whats going on with the tach/speedo/alternator.
Like I mentioned, the problem seems to occur when the weather is or has been wet and the engine is cold, so I'm wondering if it's either an electrical problem or if the mark on the damper is clogged up with dirt and oil, with the moisture aggravating the problem.
I don't really drive the truck daily anymore, but with winter coming I'll need it to be running better for plowing snow.

 

[robbiesworld]

In my experience downshifting can be caused by

Your brake pedal sagging and bumping the brake light

Your TPS going bad

Oil getting on the plug that goes to the transmission temp. sensor



If your ESS is out You just simply have no Tach No charging and it does effect your lockup and overdrive



I have had all 4 of these problems and when my ESS went bad it was just bad and never worked again. When my TPS went bad my truck shifted like crap.

 

[Loghead]

Brake pedal sagging?; presumably from a weak return spring or incorrectly positioned brake light switch?

Intriguing.

I'll certainly take a look at that, but what I'm calling "downshifting" may in fact be the TC unlocking or overdrive disengaging.



Would the TSS being bad show itself as something affected by engine temp?



Anyway, I'll certainly take a look at all of those possibilities as soon as I have the chance, and I appreciate your help, robbie.

 

[Dave M]

I replaced the ESS on my 97 5spd manual about 2 years ago and no problems. I got it at NAPA so it is probably the Niehoff brand. Mine just failed with no tach, speedo, alt not charging, MIL light on. Check to see the ESS is not dirty or crudded up and is about 0. 050 inch gap. I'm with robbie about this not being an ESS problem.



Why did you replace the ESS before and what symptoms did you have then?

 

[Loghead]

The symptoms were:

No alternator, no tach, no speedo and downshift to what seemed like second gear (I'm not really sure about that).

It's possible that there was nothing fundamentally wrong with old one, but the simple process of changing it removed the dirt and goo, so it worked for quite a while without trouble.

It'll be a few days before I can get a look at it.

 

[Dave M]

If the ESS was bad now, then the same symptoms (no tach, no alt charging, no speedo) would have returned. Since these symptoms haven't returned your shifting problem is something else other than the ESS.

 

[Dieseldemon]

Get a can of electronic cleaner from Rat Shack and spray both conns. of the speed sensor.