Truck Repair: ALDL / no reading, chilton manual, volt circuits

Question
I have a 95 GMC truck 350 4x4 1/2 ton and the service engine soon light is on and will not go off. Bought a scanner to find out whats wrong , but when I plug in the scanner I get no codes. It appears as if their is no signals coming from the aldl. When the engine will start it surges real bad.The truck was put in high levels of water in a cannel and now I have replaced the emc and replaced 3 of them already.It still does the same when I can get it started.I have had it in the shop and no one can figurer it out.

Answer
Hello Delbert,
First, get a book.
A shop service manual, or a Mitchells, Motors, or Chilton manual.
There is a section where you can test all the sensors and controls.
If you have a sensor that got damaged by the high water, and is causing a short, it could possibly damage the ecm.
If that happens to be the case, it will also damage any replacement ecm, possibly immediately.
You need to test all the items connected to the ecm for proper operating range.
An open wouldn't be too bad, but a short will blow drivers by causing too much power to flow, and the 5 volt circuits are not intended to take it.

Also, have you cought some fuel in a clean glass jar, and let it sit to see if water forms in the bottom?



Van