98 12V auto TST 230/605 plate

[disco]

Was pulling my 3500# boat up the launch ramp. In 2wd it spun the wheels so I shifted to 4wd high. Engine reved up pyro came up to 900 but truck wouldn't move. Only way I could move it was by shifting to 4wd low. Meanwhile gauges were going nuts on and off and the tach completely stopped registering anything. Back on level ground I went back to 2wd high and pulled the boat home like normal except for the instruments and check engine light continuing to go nuts, still no tach. Disconnected batteries pulled and cleaned plugs on trans control unit reconnected everything. Truck seems to drive normal (haven't tried to pull the boat yet). When I start it the tach comes up but immediately drops back to zero (all other instrument work). Ideas? Do I need to buy a code reader?

 

[GAmes]

If you open the factory service manual it will tell you how to pull what few codes are stored in the PCM. More than likely there isn't a code for no tach and instruments going nuts. You might try pulling the three connectors from the PCM and cleaning them.

 

[disco]

If you open the factory service manual it will tell you how to pull what few codes are stored in the PCM. More than likely there isn't a code for no tach and instruments going nuts. You might try pulling the three connectors from the PCM and cleaning them.

Yep did that this afternoon. Also pulled, cleaned and reinstalled the Crank Position Sensor. Only instrument that doesn't work is tach. AC is out and alternator isn't charging. I believe this indicates a Crank Position Sensor problem. Any idea how to test it?

 

[GAmes]

I don't know of any serviceability test for the engine speed sensor. That isn't to say there isn't a test, I'm just not aware of one. 24 valve engines have crank position sensors, so if you look for the proper part name you might have better luck. My FSM does have a description of it's operation. You could start with that and a multi-meter.

 

[Bob4x4]

Cummins calls it an engine speed sensor iirc