Engine/Transmission (1994 - 1998) Tach. not "Taching"

[Rdunkin]

I had a battery go bad and it would not start due to low voltage. I replaced both batteries and the tach. reads eratic. It will jump from 700 RPM straight to 2500 RPM under accelation. I think due to cranking with low voltage I may have killed the tach. I cleaned ALL cable ends and wires at both batteries.

Anyone have this problem before?

Thanks

Richard Dunkin

 

[Andy Redmond]

The pcm may be fritzing out.



Ck. the speed sensor above the crankshaft vibration dampner. The air gap s/b . 050 (don't ck. it above one of the slots in the dampner).



Also ck. the connector for this sensor near the base of the cylinder head below the upper radiator hose. Clean the connector and treat it to fresh dilectric grease.



Report back to us. .



Andy

 

[K5IP]

Andy is right on,

The engine speed sensor must be operating or the charging system won't operate.

Loss of tach indicates the engine speed sensor is not present, either because it failed, or as Andy said, because of connector/adjustment problems.

Listen to him!

Rog

 

[Rdunkin]

Charging system is working fine... ... ... . any time there is low voltage the Tach. is the first thing to go on the Dodge. Tach. reads 750 and 2500 RPM only. I will check PCM and let you know.

Thanks

 

[Howard Durand]

When you replaced the batteries, did you have them both disconnected from the truck at the same time? I have found that completely disconnecting battery power will usually allow the PCM to reset to it's default programming. I know that when I have had to disconnect the batteries for some tinkering, the OD and TC shifting usually returns to normal when they are reconnected.