Engine/Transmission (1994 - 1998) Hot day, no tach

[Balzac]

This has happened for over a year. First I thought it was the crankshaft sensor, got a new one, same problem. Now checked all wire connectors around engine, then when it happened, I shut off and sprayed almost a whole can of circuit cooler on the crank sensor. Still no tach(& no alternator,no overdrive, & no A/C each time it occurs. ) I am thinking it could be the ECM ?

If I get a used ECM from the same truck, will this work ? Any other possibilities?

1995 12V auto.

 

[GOlsen]

Definitely sounds like the ECM to me. It does control all of those things you are having problems with. Not 100% sure, but I would think an ECM from the same truck would work. If not, I hear that Advance Auto Parts can order one for you, pre-flashed with your VIN and all that.

 

[Balzac]

Actually the ECM does not think the engine is running and does not turn on the A/C, Alternator, or OD as why would it if it does not read the signal from the crank sensor that the engine is running. This leads us back to the crank sensor which I mentioned in my post. I am wondering if a wire connection from the crank sensor could be subject to heat disconnect at the ECM?

 

[hsmith]

My opinion is that all of us lucky folks with the 12 valve engines do not have to worry about the problems with the later models with ECM controls. All we have is the PCM for basic functions. THE PCM DOES need crank signal to initiate tach, chargnig, cruise, etc. Maybe a wiring issue.

 

[Missouri Mule]

Balzac,when the a/c (along with no tach,overdrive,voltgage) is affected it usually means that the engine speed sensor is not getting a ground. I would check to see if it has ground at the connector, if not run a ground wire to it.