2nd Gen Non-Engine/Transmission Tach operation erratic

[MWinters]

I have a 99 with the 5 spd manual that is bone stock. Over the weekend my Engine Service Light came on. Thinking this was an anomoly, I removed my battery cables & everything was OK for a day or so. Now my tach operation is erratic - works sometimes, other times it goes to zero - & the Service Engine Light is on again.



Any thoughts ? Is the sensor mounted on top of the rear differential the culprit( I think this is what I replaced a few yrs ago when similar symptons occured, but I can't remember !)



Thanks,



Mike

 

[Blackcloud]

I would check the sensor just above the harmonic balancer on the front of the engine. When I did the KDP on my first truck, I didn't set the sensor to balancer gap correctly and had the same problem that you are describing. After correcting the gap, all has been fine (knock on wood).

 

[gonehuntingagain]

My money would be on the crank position sensor that is mounted behind the starter. The sensor on top of the differential is a speed sensor for the anti-lock brakes.

 

[ToolManTimTaylor]

1999 trucks Have a Crank Position Sensor AND a Cam position Sensor. The Cam sensor is up behind the VP44 and just plain sucks to change :{

 

[DLausche]

Exactly what mine did earlier this summer. Was the crank position sensor. What a PITA to get that thing out! I always do repairs myself on my truck when possible, but this is one I wish I had brought to the dealer to work on.



-Deon

 

[MWinters]

crank position sensor maybe the problem

Ok guys, thanks to all who have replied. I think I'll take it into the dealer & have him do a scan first to see what the problem may be. If it's the crank position sensor, & we have 7 yr/100k warranty on the engine, is this still covered ?



Thanks again,

Mike.

 

[AHughes]

Had the same thing happen to my truck with the erratic tach and it sounded like it was missing. Ordered a crank position sensor from Cummins Northwest for about $50 including a $9. 00 core charge (they don't want the used ones getting into the aftermarkets hands) I removed the starter 3 bolts (10mm) and while I had the starter out I installed some "Larry B's" super contacts I think they were $35 with a new contact plunger. The crank sensor is held in by one bolted bracket and mine just pulled right out of the block without any problem and I inserted the new one after greasing the O ring with some O Ring lube and installing the bolt and pluging in the wire. I also put dielectric grease on all the plugs as we have the anti ice liquid sprayed on the roads here in Oregon in the winter and they wreak havoc on electrical plugs. This is really a simple fix. The hardest part is removing the 10mm bolts as you might thing they've been welded in but no. I replaced mine with allen head socket head cap screws grade 8. Hope this helps. Don't let the dealer lay you away!

 

[MWinters]

AHughes,



Thanks for the update. Makes good sense to all do the starter contacts @ the same time.



Thanks again to all,



Mike.

 

[DLausche]

... we have 7 yr/100k warranty on the engine, is this still covered ?



Thanks again,

Mike.

...

Mine was denied under warranty. I dunno why, but the CPS is not considered to be part of the "engine" and is not convered by my 5yr/100K warranty.



-Deon

 

[MWinters]

Thanks to all - I changed the Crank Position Sensor & updated with the Super Contacts in the starter about a week ago. The erratic tach problem is gone. Life is Good Oo.



Thanks again,



Mike.