Hi Guys. I have a ton of mechanical experience but very weak in electrical. I hate it. Bought a 1999 Cummins for my daughter that will be turning 16 in Sept ( she will be paying me back for the truck, lol ) and even with new batteries, if it sits for a week or more, the batteries drain to the point it will not start. 

I have tried to research this problem & have eliminated the seat belt modules are not the problem. What else could it be ?

Any help would be much appreciated.

 

On a side not, it also does what I think is a weird thing. Sometimes when you turn the key to the on position, the wait to start light doesn't come on & no matter how long you crank, it will not fire. I know the ambient/engine temp sensor monitors this but if you turn key off & then back to on, the wait to start light usually comes on & once it goes off, it fires up right away. again even with engine warm, if the wait to start light doesn't come on even for 1 sec, you can crank to the cows come home & it will never fire up. Just thought I would throw that in here, incase it has something to do with battery drain ?

Other than that, everything else works as should.

Thanks

Edited June 16, 20204 yr by Me78569

The WTS light is an ECM issue.  Excessive ac voltage from your alternator can be causing problems for it and the other electronics. Testing that voltage would be good start. First you need a good DVM, a fluke is recomended but others that read ac milivolts will work. With the engine runing and everything off place the + on the charge stud on the alt and the - on battery ground. .035 and below us good, .050 and below is marginal and anything above is not good. WT's ground mod is a good solution to help lower  the voltage also if its high. 

This will not solve your batteries draining but with the WTS issue I think its where I would start. If its getting to the ECM its getting to the other computers also.

If you don't see the WTS light then the ECM never booted and the engine is brain dead and will not run.

 

 

When you turn on the key, and the wait to start light does NOT come on,  do all the other lights come on?  Are you getting a full response or partial response from the ignition switch?

 

Since you have a battery drain, I wonder if the ignition switch is failing.  As Dripley said,  the wait to start light also confirms the boot up of the ECM. 

 

Sort your drain out first.   The cause of it may also be the cause of the WTS problem.

 

There are some good you tube videos of searching for a parasitic drain.  The basic way is to put a amp meter between the battery and the battery lead.  You will read an amperage if you have  a problem.  pull fuses until the problem goes away.   We have 2 batteries so it is a bit weirder, but you can disconnect the passenger battery, but you have the alternator connected to that one.  The alternator is a possible parasitic drain.(there should only be 2 wires to passenger battery, ALT leade and crossover to drivers battery.  If there are more, someone added them and should be checked)  

If you don't find the circuit that is fused that reduces your amperage, it will be tough.  That means that somehow some wire is attached to the batteries directly, but not fused in the panels. (there are two fuse panels one in cab and one underhood)

 

Moparman and Dripley have referred you to a possible cause of the failed WTS.  You will want to investigate it.  But finding the drain is the biggest priority.  (it could be both... if diodes are bad in the alternator you definitely made AC noise, and depending on the side of the bridge, can be a very large parasitic drain.) 

 

Good luck HTH

 

Hag

Battery drain is pretty easy to detect. Grab a good digital Multi meter with Amp meter. Pull each fuse one at a time in the PDC and cab fuse panels. Now insert the probes into the fuse socket. This will measure the current across that circuit. When the high drain is found you'll at least know what circuit. Look in the power distribution section. This wire map works for all years. 

 

 

 

Add on like amplifiers, radios, trailer brake controls, inverters, GPS and phone charges can still draw current when off.

Also check your batteries:  Are they matched -- same lot and age.  Mismatched batteries will draw to the lowest voltage, a downward spiral.  In essence the battery with higher voltage will try to charge the battery with lower voltage constantly drawing down.

Thanks guys. No aftermarket anything but a trailer brake controller.

All other lights in dash come on everytime, just a crap shoot for the WTS light, no matter what the outside or engine temp is.

Will attempt to try using meter.

Don't like the sounds of a possible ECM issue but as mentioned I will try drain 1st.

39 minutes ago, Joe_Pool said:

Also check your batteries:  Are they matched -- same lot and age.  Mismatched batteries will draw to the lowest voltage, a downward spiral.  In essence the battery with higher voltage will try to charge the battery with lower voltage constantly drawing down.

Yes, both batteries were replaced together. Same lot & age. Thanks

Grrr,

You will have an ECM issue (you are now actually) in the future....  Just know that it will not start if the WTS light doesn't cycle properly.

 

You need to go through the parasitic draw testing.  It takes time, but do it.  Amp meter between battery and truck then pulling fuses is faster than pulling each fuse and measuring amp between those terminals, but both will give you the same answer. 

 

You could find that fixing the draw fixes the WTS problem.  It is possible.  maybe 10%.   Its possible that what is causing the draw caused the damage in the ECM 20%.  the other 70% is that they have nothing to do with each other. 

 

These are not known percentages, just good guesses based on what could still be powered up and kill the battery in a week not overnight. 

 

GL HTH
 

Hag