What does the ECM do in the 1st gen? Does it do anything with the speedometer, cruise, or have any engine controls?

 

i dont know someone help this guy out

 

controls the tach, alternator charging, and something else....i cant remember right off the top of my head.....

 

The 92 doesn't have a tach, didn't think any of the 1st gens did - factory anyway.
Anybody else got clues on the computer????
By the way, how do you add a tach; where or how do you hook it up?

 

The 92's have a factory pig tail in the coulmn, Simple plug and play for a tach.

and logan nailed it.

 

Thanks once again!
I'm wondering what's the point of a computer if that's all it does??????

 

Got me...

 

Here's what I've found out about it so far. First a little back story. The sons 92 cummins battery blew up the other day. What we found was a smoked voltage regulator and bad battery of course. No other burnt wires or anything. What we don't know and probably never will is did the regulator go first and blow the battery or did the battery go and take out all the rest of the stuff/. Battery was 2 weeks old. We replaced the battery and all was well, so we thought, first thing we noticed was the heater grid was not working but thought maybe it was due to the fact it was warm in the shop. Next was the speedo not working so the trans would not go into overdrive. I put my scanner on the OBD1 test connector and no response from the pcm, it was dead. We took it out and pulled the cover only to find the magic smoke had escaped from the exposed capacitors, it was junk.
So, the PCM controls the overdrive, heater grid, ac clutch and probably more stuff.
I just happen to have a PCM from a 92 gas truck so we put it in thinking if it works, great, if not, no harm no foul. To our surprise it worked
The trans shifts better than it ever did, the heater wait light comes on and so far all the other little electrical gremlins have left the building.
Whodu thunk it
Time will tell if the PCM from the gas motor will work in the long run.

Dave

 

easiest way is to look at a wiring diagram and see what goes into it.

TPS
VSS
Grid Heater
OD
Trans Temp
RPM
Coolant Temp
Water in Fuel
Wait to start
IAT
Cruise control inputs
OD Off switch
Brake Pedal switch
Ignition feed
AC Clutch
A/C cutout switches
HVAC inputs
Alternator/voltage regulator
Ground
VREF
Speedometer
Odometer
MIL
Tachometer


Im sure I'm missing a few.