I was having problems about a month ago. Truck cranked but wouldn't start. Check engine light on, codes present were 1688, 1689, 252, 254. Injection pump was replaced. Same problem, same codes. Took to local Chrysler dealer they cleared codes and said nothing was wrong. Drove to get fuel, truck was idling and just died and cranked but wouldn't start. When it finally started it wouldn't go above 1500 rpm's drove home on shoulder 8 mph. Sometimes when key is in the on position waiting for start light speedo needle with jump up and down and CEL will flash on and off. Help please!

Sound like a ECM issue coming on. I would check the alternator first of for AC noise output from bad diodes.

Then once you know you got clean power and no AC noise issues then I would try swapping ECM's with someone and see if the problem goes away. If so then you know the ECM is failing and requires replacement.

Alternator was recently replaced. I can get a rebuilt ecm for about $300.00 but it will need to be flashed and I don't know where to get that done, cost? I cannot read the part # on ecm. Will my VIN tell what the original part # was?

Alternator was recently replaced. I can get a rebuilt ecm for about $300.00 but it will need to be flashed and I don't know where to get that done, cost? I cannot read the part # on ecm. Will my VIN tell what the original part # was?

Just because the alternator was replace doesn't mean it clean power. Read more here... http://forum.mopar1973man.com/threads/5937-Torque-Converter-Lock-Unlock-Issues?p=63884#post63884 Any ECM will work basically its just the software that is different and yes the VIN and a few other tags will tell all about the vehicle and what it requires for software. As for the reman'ed ECM's most end up with expensive paper weights. Some have been lucky...

If I Pm you my VIN can you tell me the part# of my original ECM? The rebuilt ECM has a 2 year warranty. So the problem could be with alternator?

f I Pm you my VIN can you tell me the part# of my original ECM?

I won't be able to tell you but maybe a dodge Dealer could. As for electronic failures I'm finding that 90% of then stem from grounds, battery issues, alternator noise, etc. Being that electronics typically will last a very long time on just battery power but introduce noise to the power it will cause damage for sure. The other 10% is environment. Maybe the ECM is seeing serious high temps from a overheating truck.

How do I hook up to test alternator? I found the part #'s for ECM, Cummins part # 3947412, Mopar part # 38331300J. Can anyone reccomend where to get an ECM?

How do I hook up to test alternator? I found the part #'s for ECM, Cummins part # 3947412, Mopar part # 38331300J. Can anyone reccomend where to get an ECM?

I typically use a high quality DVM like a Fluke or similar. check you DC volts then flip to AC and see if its over 0.1 Volts AC if its higher its a fail.

http-~~-//www.youtube.com/watch?v=UveGtGuswBw

Am I testing across battery terminals? I have a cheap tester hope it will work.

Am I testing across battery terminals? I have a cheap tester hope it will work.

Yes across the battery terminals. Look at your DC volts then flip right over to AC volts it should not be above 0.1 volts.

Battery 14.32 on DC setting. AC fluctuates between 30.7 and 30.8 on 200v (lowest setting}

Battery 14.32 on DC setting. AC fluctuates between 30.7 and 30.8 on 200v (lowest setting}

Is that actual voltage or are you reading Millivolts being you are on the lowest setting on AC? It should read V or MV in the lower corner of most meters.

Yes it is on the 200V AC setting the lowest setting with the wavy line above it. 30.7 is that even possible? I have a new alternator coming tommorow can i test it on the bench for AC voltage?

I tested mine today with the Ac 20V setting. Came out 0.01

200V AC is the lowest setting on both of my testers. Still showing 30.8 on 200V setting, on 750V setting shows 030.