Check engine after alternator change

[JeepWoods]

Got a 1997 TJ 2.5. 5 speed. I Just changed the alternator because the old one was seized up. After changing the alternator now the check engine light is on and the codes it giving is 37 and 25. Any help I’d really appreciate it. It did not have the CEL on before I began. All the gauges bounce to very irractic. I know this are the code but not sure where to begin and if it has anything to do with changing the alternator. 25** A shorted or open condition detected in one or more of the idle air control motor circuits. Actual idle speed does not equal target idle speed.37** Relationship between engine speed and vehicle speed indicates no torque converter clutch engagement. An open or shorted condition detected in the torque converter part throttle unlock solenoid control circuit. Incorrect input state detected for the Park/Neutral switch. Auto only.

 

[Steel City 06]

Do you have a voltmeter? If so, what is the voltage when the engine is off and when it is running? It’s possible the new alternator has bad controlling circuitry and is sending either low or high voltage.

It could also be a failure of the PCM to interface with the alternator.

Are the connectors corroded? If there’s not good contact, the charging system can cause some odd intermittent issues. If so use steel wool or another abrasive to make all contacting metal shiny. Double check that the connections at the alternator post and battery terminals are secure.

 

[JeepWoods]

So after further investigation I took the alternator back off and when doing so I noticed that one of the terminals wasn’t tight and wouldn’t tighten up. So I removed the nut that was behind it and it allowed me to tighten the terminal up where it needed to be. I also cleaned all terminals and charged the battery all the way up just to make sure that wasn’t the problem. Sure enough no check engine light and no codes!! Back to jeepin!

 

[Steel City 06]

Great news!
And welcome to the forum!