Engine/Transmission (1994 - 1998) alternator,a/c,tach,odometer out. Help!!

[diesel974x4]

I have a '97 2500 4x4 5 speed longbox ext. cab truck. The engine is a 12 valve. The speedometer, odometer, tachometer, "wait to start" light, A/C, and voltmeter (usually reads 14 volts, now reads 12) have quit working. My friend and i played around with it for awhile, checking electrical and fuses and such, basic stuff. I looked inside my chiltons manual and all it talked about was the speed sensor on the transfer case. We disconnected it and looked at the connection, it was clean. So we reconnected it and checks the tach sensor and did the same thing. We checked for continuity on both and they were good. So we thought maybe it was the sensors themselves. We tried starting and stopping the engine a couple of times, nothing. Then later that night i drove to the store and everything worked. It worked for about 5 or 6 days then went out again. It hasn't worked since and that was about 2 weeks ago. I've been poking around with alot of things and i replaced the speed sensor yesterday. It was a different style with the same colored wires so i cut the old connector and spliced in the new with heat shrink tubing and electrical tape. It still didn't work. I would just like some opinions or advice. My alternator works, but only puts out 12 volts and not the regular 14, so it starts, but runs off the batteries. the alternator doesn't charge the batteries. Everything i see points tward the PCM, but i don't want to mess with such a delicate item without knowing for sure. The truck runs and drives fine, just no charge and everything else. Any assistance would be appreciated. Thanks. Bryan

 

[NCovey]

I had one recently that the a/c, tach, & alternator quit, as well as incorrect shifting. It was the crank sensor. With out it the truck will still run, but the pcm doesn't know it, so it won't tell the other systems what to do. -Nicholas

 

[diesel974x4]

thank you nicholas! I will try that. I've looked all over in my chiltons manual though and it doesn't say anything about replacing the tach sensor. was wondering if you or anyone else has got a schematic or details about installing one. I see the plate is adjustable and was wondering what the gap was or if there is one. Thanks, bryan

 

[DavidC]

Be sure to check the wiring from the sensor to where it plugs into the engine harness as there has been some wiring issues in that area with those systems.



Dave

 

[KWentling]

It's called the engine speed sensor, located on the passenger side front of the engine and reads a slot cut in the harmonic balancer. It should have a gap of . 049 to . 051 checked with a nonmagnetic feeler gage. Some use a credit card to set it.



Kim

 

[Missouri Mule]

Could be bad ground for instruments (I believe the ground is located near radio) or broken ground wire.

The engine speed sensor (crank speed sensor) should not take out

speedometer or odometer, 'wait to start" light.



The engine speed sensor will take out tach,ac,voltemeter, some auto trans functions, cause engine to stall. Usually because dirty connections, bent pins or bad ground.

 

[Flinty]

The exact same thing happened to my truck. Unplug the engine speed sensor, some manuals call it the crank position sensor, if the wait to start light comes on, replace the sensor. If it doesn't come on check all connections. If that doesn't bear fruit then have the power control module (p. c. m) checked. Pray it isn't the pcm. If the pcm doesn't get a signal from the engine speed sensor it will shut down charging, tach, speedo, etc. It thinks the truck is not running. Upon replacing this sensor all functions came back online. luck.

 

[diesel974x4]

thanks to all for the information. I will try the tach sensor and hope that is the problem. I appreciate all the information. Bryan

 

[Willys]

I bumped the (ESS)connector loose on my '96 while changing the water pump and lost some of the gauges- tachometer, voltmeter, etc. I didn't drive it any until I found the loose connector, so I don't know if the speedometer was affected. I would expect on a '98, where the gauges are more electronically based, that it would be affected. On a '97 I'm not sure.



Hold the connector tight with a zip tie.