Alternator light

[Legbah]

I replaced the alternator on my '08 ram 3.7. Reset it both ways, placing the positive and negative cables together for 30 sec and also separately pulled the PCM fuse and heard the three dings. Now, occasionally, it will run rough and the alternator light will come on. Sometimes it does it right after start up while backing out of my driveway, sometimes it happens out of the blue while driving. I pull over turn it off and restart it and it's fine. After restart it is smooth and works great. Is this a PCM/ECM problem? 271 K miles.

 

[jws123]

Did you scan the truck for codes? what brand alternator did you use? Check it with a volt meter to see if its actually charging .Your issue could also be your throttle body if the alternator checks out.

 

[Legbah]

I've been thinking it might be the alternator. Thanks. The alternator came from carquest. It's charging fine, I put a new battery in it last year. It will act like it's missing, very rough then the red lighting bolt pops up. Thank you for the advice.

 

[Legbah]

I meant the throttle body. That's probably the problem. It was left for dead. I put a used trans, new alternator, new plugs, new fuel sending unit in the tank, new battery in it. Someone really messed it up before me, EGR delete with JB weld to fill the EGR port on the back of the engine.

 

[jws123]

Well i can say carquest parts are the worst especially for alternators and starters but you need to for sure scan the truck.

 

[Legbah]

I will, but your theory of the throttle body triggering the rough idle then alternator light coming on makes sense.

 

[Legbah]

Also a PCM is about 250 bucks preprogrammed. I’m going to dismantle a 06 hemi ram. I’ll learn from that. Blown engine, trashed interior. My parts truck.

 

[Rlaf75]

Before you do anything else, I would check for codes like everyone has already mentioned. You can keep throwing parts, time and money at it in hopes of eventually fixing the actual problem or you can scan it for codes to see if there are any that can lead you in the right direction. I also recommend using a scan tool that supports live data so you can actually see things as they happen. With that said, good luck

 

[Legbah]

Thank you Rlaf75. I appreciate the response. I’ve got a scan tool. Launch Touch Pro Elite.