[RollDUPwood]

Hey guys. Left work today and went over some railroad tracks and I noticed my speedo and tach went out. I then noticed my odometer was not working and my batteries were not charging. The truck still drove and I made it home. Got on here immediately. I’m going to start checking loose connections but I figured I’d start this thread hoping one of you guys knows exactly what the problem is. I’m thinking ESS…. Any help would be great. If I figure it out before then I will post. Thanks

 

[9297oldram]

Check the ESS gap should be .050

 

[RollDUPwood]

Check the ESS gap should be .050

With a metal feeler gauge?

 

[9297oldram]

It's ok i've used one many times, or a credit card I hear they are close.

 

[RollDUPwood]

Air gap is .50 with slight drag. Connection looks good.

 

[GAmes]

I’m thinking ESS….

It's been posted dozens of times that the ESS has nothing to do with the speedometer.

 

[RollDUPwood]

It's been posted dozens of times that the ESS has nothing to do with the speedometer.

If I type in NO TACH NO SPEEDO and filter it for 94-98 almost all of the searches reference replacing ESS. So I have no idea.

 

[foresterfields40]

Check all your grounds

 

[9297oldram]

If I type in NO TACH NO SPEEDO and filter it for 94-98 almost all of the searches reference replacing ESS. So I have no idea.

But just type in no speedometer and see what the fixes are. The other problems could be the ESS.

 

[GAmes]

If I type in NO TACH NO SPEEDO and filter it for 94-98 almost all of the searches reference replacing ESS. So I have no idea.

Because the same non-logical guesses are rampant. Do any of them show the ESS fixing the speedometer?

The logical way to troubleshoot would be to determine what the speedometer and the tach have in common. That requires opening the factory service manual and searching for a common link. More than likely that common link is a ground.

 

[yogibayerdvm]

I would look for a single fix. It would be odd for more than one thing to go at the exact same time. Not impossible just unlikely

 

[9297oldram]

I would look for a single fix. It would be odd for more than one thing to go at the exact same time. Not impossible just unlikely

When I junked out my 97 I saved the wiring to reuse and there was numerous grounds that had up to 6 individual wires on a terminal.

 

[RollDUPwood]

Because the same non-logical guesses are rampant. Do any of them show the ESS fixing the speedometer?

The logical way to troubleshoot would be to determine what the speedometer and the tach have in common. That requires opening the factory service manual and searching for a common link. More than likely that common link is a ground.

Yes I have an FSM just didn’t have it with me yesterday. I’ll look through it after work. Also the ac compressor doesn’t kick on.

 

[RollDUPwood]

I would look for a single fix. It would be odd for more than one thing to go at the exact same time. Not impossible just unlikely

I agree.

 

[texasprd]

...Also the ac compressor doesn’t kick on.

Tach, charging, and AC compressor will be inoperative if there is no ESS signal. But as others said, that should not affect speedometer or odometer. As said above, look for something in common

 

[jimduchek]

Just going to copy/paste myself from a previous post lol. Do you get bulb checks (WTS, WIF, etc?) when you turn the key on?

If the alternator wasn't charging but you get a GEN light on the dash -- alternator bad.
No tach, no charging, but speedo works -- ESS issue.
Tach+charging, no speedo -- VSS issue.
No tach, no charging, no speedo, no bulb checks -- PCM is bad (Maybe not fried, maybe just power/ground issues)

 

[RollDUPwood]

Just going to copy/paste myself from a previous post lol. Do you get bulb checks (WTS, WIF, etc?) when you turn the key on?

If the alternator wasn't charging but you get a GEN light on the dash -- alternator bad.
No tach, no charging, but speedo works -- ESS issue.
Tach+charging, no speedo -- VSS issue.
No tach, no charging, no speedo, no bulb checks -- PCM is bad (Maybe not fried, maybe just power/ground issues)

No TACH, No ODO, No CHARGE, No SPEEDO, No AC COMPRESSOR, No WAIT TO START, No GEN LIGHT. I’ll be checking stuff when I get home. Thank you.

 

[RollDUPwood]

Tach, charging, and AC compressor will be inoperative if there is no ESS signal. But as others said, that should not affect speedometer or odometer. As said above, look for something in common

No TACH, No ODO, No CHARGE, No SPEEDO, No AC COMPRESSOR, No WAIT TO START, No GEN LIGHT. I’ll be checking stuff when I get home. Thank you.

 

[RollDUPwood]

So after looking at some diagrams it appears that the relationship between the ESS and the VSS are circuit K4 sensor ground. I unplugged the ESS and the SPEEDO works and my CHECK BULBS now work. But no CHARGE still which makes sense because the computer doesn’t know the truck is running without the ESS plugged in. I tested the connector at the ESS with the truck on and I get 5 volts between the 5 volt supply and it’s sensor ground which is K4. I’m assuming the ESS is bad and when plugged in is shorting that sensor ground. Any thoughts?

 

[GAmes]

More likely is one of the wires to the ESS is grounding out. I found mine rubbed through at the front of the engine. The engine speed sensors do fail rarely, but it's an expensive part to just throw at the problem.