How do I test the alternator and ECM to see if either is failing?

[CharlesHS]

The Battery Temperature sensor provides information to the PCM to adjust the charge rate for the battery when outside air temperature is cold.
The problem you are experiencing may be as simple as the Battery Temperature sensor in the battery tray may be bad or the wiring for the sensor could be frayed or even broken.
You should inspect the sensor and its wiring to see if there a simple way to resolve your problem.

 

[Walkerman]

20 minutes if you've done it once or thrice.

-Mac

Thanks

 

[macleanflood]

On my 97 with AC I can take the alternator out the back and then up. Pulling the coil is easy and might give you more space. Most of it's done with a 15mm rachet and box wrench. Disconnect the battery, take off the belt...undo the wires on the back...undo the top and bottom bolts and bring it slightly up and passenger and then back into the cavity by the distributor and up.

-Mac