Engine/Transmission (1994 - 1998) Tach doesnt work

[BrandonThompson]

Just bought a 95. The tach doesnt work at all and neither does the cruise or a/c. The rest of the guages work and the speedo works. Any thoughts

 

[RT66DOC]

The pickup sensor is on the crank dampner - sits to the left /pass side of top center. That's all I know about it. I'm electronically challenged but others here can help you out . Welcome to TDRland.

 

[Howard Durand]

Check the engine speed sensor. It may be bad, the connector might be dirty or it may have a bad ground.

It might also need to be adjusted. I think you want about 0. 050" between it and the dampner. Use a non magnetic feeler gauge to check it.

It is located just above the vibration dampner on the front end of the engine. The connector is close by at the top of the block.

Pull the connector apart and douse it with electrical cleaner. Check the ground too.

All engine components are grounded at a bolt in the head located on the driver's side of the #1 valve cover.

If that is not the problem then the PCM may be bad.



You should have 8 volts on the orange wire. The black wire is ground. The grey wire is the signal to the PCM.



Hope this helps.

 

[DCTECH]

If the PCM don't know the engine is running with the rpm signal from crank sensor it will not let a/c, cruise, tach, and alternator work.

 

[BrandonThompson]

The voltgauge in the truck appears to be working and i assume the battery is charging.

 

[Howard Durand]

The voltmeter isn't dependent on the PCM but voltage regulation is.

If the charging system is working your voltage should read in the range of 13 to 14 volts. If not it will be actual battery voltage of 12 volts or less as the load increases.



The indications are that either the VSS or the PCM is bad.

 

[DCTECH]

Volt gauge will work but with 2 batteries depending on electrical accessories being used I have seen trucks run and start ok from anywhere3-4 days to a week before owners notice voltmeter running lower or having starting problems.

 

[BrandonThompson]

Checked the alternator today with a volt meter. It appears to be charging 14 volts. I think i will still replace the sensor and see if that fixes the problem. Thanks for the input

Brandon

 

[BrandonThompson]

Thank to all who replied. I installed the new Crank speed sensor and the tach works, AC is cold and cruise works. TDR has saved me alot of time and money already. Thanks again.

Brandon