Bucking on warm starts

[Dirty]

First time posting but love this site. 

I have a 99 Dodge Cummins. Roughly 160,000. This issue started roughly 6 months ago. The truck runs great until a warm restart. Then in bucks and surges a bit when I hit the throttle and eventually goes into limp mode. It has never done it on a cold start. I can put money down I can start it in the morning and it will be fine. I’ll drive to town with no issues. If I shut it off go into a store and come out it bucks and surges then goes to limp mode. It results in a p0606 code. 

So when it first did it I changed the APPs out to a Timbo apps. I have also changed the MAP and IAT. I sent the ECM off to get repaired. Oddly enough when I got it back it ran great. Way more power then it had. However I then developed the torque converter lock up issues. I did all the usual stuff. Moved the ground cable that runs by the alternator, foiled it, and added the BD noise suppressor. Cured the torque converter lock up issue. Thought I had her licked. Drove it today about 10 miles...went into a store....when I came out and started it the problem came back. Not sure what else I can do. Alternator noise seems to be low. I’ve gone through all the grounds. 

Any thoughts?

[Dieselfuture]

7 minutes ago, Dirty said:

Moved the ground cable that runs by the alternator, foiled it, and added the BD noise suppressor.

WT mod and check ac noise is the first thing to get done. Then check all other cables/grounds, then we go from there.

 

8 minutes ago, Dirty said:

Alternator noise seems to be low. I’ve gone through all the grounds. 

How low? Just what you said foil and bd isolation this means you have electrical issues.

[Dirty]

I apologize I didn’t take down the numbers of the AC test.  I just know when I checked it it seemed in range. I’ll check it again tomorrow and post the results. 

I feel confident my grounds are good. I’ve been slowly eliminating all the low hanging fruit over the last 6 months. 

[dripley]

These are very good signs of excess AC voltage. I have to agree with what @Dieselfuture says. Dont assume anything is good with out checking it. The trucks thrive on good clean DC voltage. 

[Mopar1973Man]

12 hours ago, Dirty said:

Moved the ground cable that runs by the alternator, foiled it, and added the BD noise suppressor.

 

Take all that junk out and do the W-T ground wire mod. I'm only 11mV AC for alternator noise. 

 

 

[Dirty]

So started truck today and checked AC voltage. .02-.03. Ran up town and when I got back checked it again .06-.08. 

Brought it into shop and finished WT mod. 

Took it for a 10 mile drive and same ol story. When I got to my location I shut it off, went into my parents house for about 10 mins. When I went to leave it surged and went into limp mode. 

I got p0606. Just to throw some more info out there the truck always has code p0380. I can’t seem to erase it. Once I clear p0606 the CEL comes on with code p1689. I can clear them and get out of limo mode but it doesn’t matter. It will surge and kick me back into limp mode. I’ll go home, unhook batteries, and it will run fine in the morning. 

Thoughts?

[Mopar1973Man]

3 hours ago, Dirty said:

Once I clear p0606 the CEL comes on with code p1689. I can clear them and get out of limo mode but it doesn’t matter. It will surge and kick me back into limp mode. I’ll go home, unhook batteries, and it will run fine in the morning. 

Thoughts?

 

ECM is fried from AC noise damage is done. This is the second round of P0606 code so I'm sure that your ECM needs to be rebuilt.

 

3 hours ago, Dirty said:

I got back checked it again .06-.08. 

 

Fail. Anything over 0.05 is a fail... So yeah the alternator cooked the ECM...

[Dirty]

Just before I send it out again...why is it I would only have issues on warm restarts? 

[Mopar1973Man]

Because the ECM has already lost it mind from the high AC voltage. Hence the P0606 code. Now with margin parts inside the ECM all it takes is a bit of heat and it gives up.

[Dirty]

10-4

Now with the alternator...should I be changing it with a direct replacement? Really want to make sure I’m taking the steps to not deal with this again. This has been a nightmare. 

[Mopar1973Man]

9 minutes ago, Dirty said:

Now with the alternator...should I be changing it with a direct replacement?

 

Basically you can buy a rebuilt ND or Bosch alternator. BEFORE leaving the store make sure to have the new one bench tested. I've actually bought brand new alternators that are bad in the box. Now once that is done then make sure to do the W-T ground wire mod, then you might want to do the PCM protection fuse mod. Have both batteries tested if one fails replace both. Then do a voltage drop test of all the cables. 

 

Ground wire mod reduces the AC noise considerably for the entire truck... The alternator protect fuse mod stops any kind of short to the blue wire from burning up your PCM. Then the voltage drop test can be used anywhere in the system to measure voltage loss on cables and connection so they can be repaired. 

 

[Dirty]

Appreciate the info. I got some work to do. Hopefully in about a week I’ll post good news. 

[Mopar1973Man]

The sad part is someone as a member here or members have had this kind of problem. Hence we post about it and share what is going on and create articles so we don't forget how to fix said issues. This what makes M73M different from other web forums. We work to solve puzzles and then save the solution to the said puzzle as an article. That way other members that find their selves in this issue have a much greater chance of fixing said issues.

[Dirty]

So taking this step by step....I have the WT mod done and just changed alternator. When I first started truck I had .04-.05. It was cold and grid heater was cycling. When it cycles my meter would go everywhere before settling back on .04-.05. 

I let it run for roughly 10 mins. Checked it again and got .035. 

Does that seem right? That’s roughly what I got when I did the WT mod with the old alternator on. 

Trying to knock out this AC noise issue before I remove the ECM. 

[Mopar1973Man]

Make sure to drive the truck a good 10 minutes and test again. Grid heaters running will make the number inflated. You will always gain more noise at high loads IIRC the test stands in part store typically fail somewhere at 1.1 to 1.4 volts AC at full load. Lowest number here is best.

[Dirty]

Just a update....got the repaired ECM back. Installed and it looks like its dead. Doesn’t bump fuel pump, no WTS, and cranks with no start.  I contacted the repair service and they had suspected processor from the start. They refunded my money and I ordered a “new”. Guess it will have to sit a little longer. On a different note I dumped the ECM plug bolt while I was trying to figure out what was going on. Does anyone have any specs on that bolt? Not a huge deal. I think I’ll be able to find it when the weather clears but just in case any info would help. 

[Mopar1973Man]

Sorry I've got no idea on the Allen screw but I can most likely assure you that the Allen screw is metric. 

 

As for the ECM WTS light is dead clue being it did not come on the ECM is not booting up. 

Edited March 26, 2021 by Mopar1973Man