Need help think I may have a bad ecm

[Rigtruck92]

I have a 99 cummins and it started to cut out at high rpms I though maybe it was the lp wo I did a volt test and it was putting out 13.1 volts checked the fp ar idle its sitting at 15psi changed fuel filter then added lucas additive. Yesturday my radio quit working but still has lights on it no dome light and no power to the diagnostics port if checked all the fuses they are all good. I have been told it could be a bad diode in the alt putting out ac noise and iv also been told bad ecm. I do have an issue with with my positive cables on batteries always getting super corroded not long after I clean them. I need some help here before I go dump a pile of money in this thing.

[JAG1]

Welcome to the forum.

 

Just a few thoughts....

   15psi at idle probably isn't enough when running down the road. Especially true if your still on the stock fuel system.

 

   Most all of us have Half in fuel lines with a fuel pressure gauge and aftermarket lift pump to hold above 14 even under heavy uphill loads.

 

   One tell tale sign of a bad ECM is if the wait to start light acts up.

 

   Most all of us on the forum has installed the aftermarket lift pump with the wire harness that lets the ECM  only trigger the power to the lift pump. Running the lift pump off the Ecm is hard on it and damaging in the long run. You want the power coming off the batteries in which the ECM activates the relay connecting/ getting power off batteries. Sorry about being repetative. Others here are very helpful on how to set up your truck properly for the long haul and will chime in. Please do feel free to ask all the newbie questions. We like to help around here.

 

Oh yes, there is loads to learn in the article data base and will help enormously. and put a few drops of oil on the battery connections after you clean them, but you probably need to check/ clean engine grounds and everything you can.

Edited August 12, 2018 by JAG1

[Rigtruck92]

Well yesturday my wait to start light completely stopped coming on and now I have to crank on the truck for a while to get it to fire. I have an after market lp airdog and the instructiona say to set it at 15psi ar idle

[JAG1]

Are you running stock size fuel lines? 

 

Most on this forum like to see 19 psi at idle and no more than 4 psi drop on acceleration. This important to keep the fuel pressure above 14 all times.. You also need to start running 2 stroke oil in the fuel to get fuel score values within Bosch specs for the injection pump life. Otherwise its in slow death mode.

 

Go to the article section to see which ECM rebuilders are recommended by other members.

[Rigtruck92]

I have a big line kit that came with the lift pump but it is just s line that goes from the lp to filter housing . I have found a few places that will send me a plug and play ecm but I wanted to help verify that was the problem before ordering one

[JAG1]

Don't get in a hurry, wait till someone else confirms your ECM is out, which I'm hoping others will chime in and confirm.

 

Do you have the lift pump wire harness and relay that powers the L/P off the battery controlled by the ECM? Want to make sure the Ecm is protected before you go putting on another is all.

[dripley]

Have you checked for trouble codes? Though it does appear you have ECM issues a little research is better than throwing high dollar parts at it.

 

A word of caution on ECM's, there are a lot of rebuilders out there. We do have a short list of ones folks have had good luck with. So be careful who you buy from.

[Dieselfuture]

https://autocomputerspecialist.com/shop-now?olsPage=products%2F1998-2002-dodge-ram-cummins-diesel-59ltr-i6-ecm-ecu-repair-service

 

You have to be very specific with these people but they can fix it. I sent my spear ecm from a donor truck to flush it to work on mine and have 3/6cyl high idle. Everything worked for a day and then I lost my tack, called them and explained, they said you only payed for programming to repair your need to send it back and be specific on what it does and what codes you have. Because they will only fix what you tell them not the entire ecm, I guess they said because it takes way to long to figure it out. Another option they have more expensive, but no more bs.

https://autocomputerspecialist.com/shop-now?olsPage=products%2F1998-2002-dodge-ram-cummins-diesel-59ltr-i6-ecm-ecu

 and send yours as a core.

I would call them and see what they tell you. They seem to want to help but can be a bit hard to communicate with. 

[Mopar1973Man]

10 hours ago, Rigtruck92 said:

Yesturday my radio quit working but still has lights on it no dome light and no power to the diagnostics port if checked all the fuses they are all good.

 

Missed one. The IOD fuse. Has the little Yellow cover. Flip the lid open and pull the fuse out. IOD (Ignition Off Draw) fuse is blown for sure its the one that does the doom lights, radio, OBDII port etc.

 

10 hours ago, Rigtruck92 said:

I have been told it could be a bad diode in the alt putting out ac noise and iv also been told bad ecm.

 

Pull the alternator and have it bench tested. Make sure they test for ripple AC voltage.

 

10 hours ago, Rigtruck92 said:

I do have an issue with with my positive cables on batteries always getting super corroded not long after I clean them.

 

Two things cover the positive cables with engine oil they will never rot again. Then the only reason why the acid on to like that either the batteries are over charging or the batteries are damaged. So again here we are testing the alternator again and the batteries. Since the PCM can't detect AC voltage charging it can stack up on the charging. 

Edited August 12, 2018 by Mopar1973Man

[Rigtruck92]

Ok I will bet the alt bench tested and will also check the iod fuse. But would the iod fuse or ac noise be causing me to not have a wait to start light?

And thanks for everyone's input iv been ready cummins forms for days but none of them related to my exact problems so I decided to jump on here to see if that would help. I will run some more test and keep you all updated.

[Mopar1973Man]

16 minutes ago, Rigtruck92 said:

But would the iod fuse or ac noise be causing me to not have a wait to start light?

 

Well, I would check for error codes first after the IOD fuse is replaced. IAT sensor errors (hi or lo volt codes) might play a role in the light issues. P0381 code basically, in a nutshell, is an error for wiring to the WTS light which may be present.

 

On warm summers days it doesn't take much for keeping the WTS light to a very short bulb test. Now if the WTS light doesn't come on the engine will not start or run at all. This would be a sign of the ECM failure because the very first instruction is to light the WTS light up and check grid heaters. If the ECM doesn't boot up, the power relay will not turn on for the VP44 or turn on the lift pump will not power up either. 

[Rigtruck92]

Ok I'll get that fused tested then run a scanner again . The wts light does not come on at all but the truck will start after cranking on it for a little bit and it runs fine other than it cutting out ever now and then on high rpms or cruising down the hwy. I bumped the starter to see if my lp was getting power and it would turn on for a split second then kick off it wont cycle for the 25 seconds.

[Evan]

There a rail of electrical connections with I think 3 cables bolted to it below the drivers side battery. 

My truck was doing all kinds of funky stuff. Not starting, slow crank, shut off while running, I thought for sure something expensive. Turns out the nuts were loose on those cables. Tight end them up and all issues went away.

I've since seen the same on two other trucks

 

Good luck

Edited August 12, 2018 by JAG1

[Mopar1973Man]

37 minutes ago, Rigtruck92 said:

I bumped the starter to see if my lp was getting power and it would turn on for a split second then kick off it wont cycle for the 25 seconds.

 

Can't do a prime cycle after the engine has been ran. Turn the key off wait 30 seconds. This allows the ECM to fully shut down. Now bump the starter. It should run the 25 seconds. If the engine has ran for any length of time the prime cycle is locked out. This prevents the ECM from running the prime cycle during a vehicle accident.

 

40 minutes ago, Rigtruck92 said:

The wts light does not come on at all but the truck will start after cranking on it for a little bit and it runs fine other than it cutting out ever now and then on high rpms or cruising down the hwy.

 

That could be air in the fuel possibly. What is your fuel pressure like? Does the fuel pressure snap to pressure instantly or does it slowly rise up? You may just have a suction air leak and pulling air into the system but we need to know what you fuel pressure is like during these times. 

 

Here watch a video I made...(Kind of old) Watch the first crank cycle you'll hear the air bubble get to the lift pump then the pressure falls right off. This was as a suction air leak. This why I re-did the second time because now you can see the 50% duty cycle of the ECM pulsing the lift pump. The P1689 code could be caused by a bad fuel pump relay (no power to the VP44). Again ECM that is braindead will not pulse the lift pump at all nor will the VP44 fire up. 

 

[Rigtruck92]

If I bump the key the pressure will jump to 15psi the drop straight to zero. I want having any problems till recently I changed the lift pump and injection pump in October ran great ever since then. I found an ecm and battery cables. A friends has them I can get both for 500$ I'm debating on just getting both and putting them on.

[dripley]

At key on you should get that little bump you describe. If you turn it further and just bump the starter, no engine start, you should get the 25 seconds of fuel pump run. It is 2 separate actions.

As far as the used ECM, it needs to be a near perfect match on the trucks for it to work on yours. 

Are the cables used also?

Edited August 12, 2018 by dripley

[Rigtruck92]

The lp doesnt do anything when I just click the key on but when I bump the starter it just jumps to 15psi then instantly turns off the cables are used as well but he said they were both on a good running truck

[Mopar1973Man]

14 minutes ago, Rigtruck92 said:

I found an ecm and battery cables. A friends has them I can get both for 500$ I'm debating on just getting both and putting them on.

 

Be careful there... ECM software there is roughly 53 different versions of software out there. Don't randomly just buy an ECM. Then there is change up like cam and crank sensors to just cam sensor (which actually is the crank sensor when you look at pin numbers). Software wise there was differences between automatics and manuals. Then I've found some versions of ECM software not all compatible with all years of PCM's. Remember the PCM is the primary computer and the ECM is secondary! 

 

If it came down to ECM replacement I would suggest one of the rebuilder over risky buying of someone else ECM that may or may not work for you!

 

Battery cables. I would just rebuild the ends with fresh military terminals and copper lugs soldered to the cable. 

[dripley]

Good advice above. I redid my battery cables about a year ago with 2/0 welding cable and soldered ends on military terminals formabout $140. Quite easy to do.

[Evan]

Might check out Larry Bs if you just want to buy new cables