99 Dakpota starts and dies, security light on

[shadango]

Ok, I know its not an ebody....I swear we used to have a section for "other mopar" stuff....?

Hoping its OK to ask this electrical question here...we have some awesome brains on this forum and my dad-in-law could use some help figuring this one out....he was in the auto biz for a few decades , til about 95 or so I think and he knows his stuff on older cars...but all this computer age crap has us both stumped.

He has a 99 Dakota with the 318. 4x4.

The truck sat during the winter and he started it once every couple weeks. But for one month it just sat cause he was sick and the battery went flat.

Recharged battery and started having issues since.   battery checks out fine, and he tried two other known good batteries.

Truck will crank and start....but....

Overdrive, ABS, shift indicator light, Check engine , security, cruise control lights all illuminate while the engine is running. Security light goes out

Gauges are all dead....

The truck will run for 3-4 seconds then die, security light comes on again.

Turn ignition on, flicking it off and on a few times, the gauges will all start working, but leave it on and watch them, after ten seconds they all die again.

You can hear the fuel pump come on when you power up, there is fuel pressure to the rails and there is gas in the rails.

Have tried disconnecting the battery and turning ignition on for 30 seconds then depressing gas pedal .......reconnecting battery. First few tries resulted in no start at all. After a bunch of tries it will crank and run for 3-4 seconds again as above.

Any ideas here? Seems to me like it is stuck in a security mode maybe? But how to get out of it?

Or is it something more serious? But it just sat a month....what could go wrong just sitting?

I have seen references to clusters going bad and busses going bad....but again.,..from just sitting and a battery dying.

The security light coming on keeps sticking in my head....

Thanks for any help!

[shawge]

Have you tried seeing if codes are stored either through OBD or the key on/off method?

[shadango]

Have you tried seeing if codes are stored either through OBD or the key on/off method?

Yeah, he tried hooking up a tester and it said no codes were stored.

[Chryco Psycho]

With Mopar you do not need a tester , just turn the ign on & off 3 times  without starting & the gauges should display all P codes , it should at least have the battery disconnect ode . You an try disconnecting the battery again let it sit for a few minutes & reconnect it

[shadango]

With Mopar you do not need a tester , just turn the ign on & off 3 times  without starting & the gauges should display all P codes , it should at least have the battery disconnect ode . You an try disconnecting the battery again let it sit for a few minutes & reconnect it

He's tried disconnecting the battery a dozen times......each time charging the battery overnight etc....no dice

He said he also tried "flipping the ignition on and off several times" and then it started and stayed started longer but none of the gauges etc were working......he shut it off, then restarted and it started doing the same thing....ran for 3 seconds and shut off, the security light coming on.

That seems to be a clue, to me....but how to break out of the loop he appears to be in?

That, or the CTM is bad maybe?? But how does a CTM go bad just sitting.

He is going to pull the connectors off the CTM and check for corrosion....I also suggested he check the ground points on the truck...maybe one broke.ent bad??

[YellowThumper]

I would check the battery to confirm it still is good under load.

My dak did that a few years ago when the battery went bad. Would charge up and try to start but had an internal short that was a huge draw on alt when firing it up.

[shadango]

I would check the battery to confirm it still is good under load.

My dak did that a few years ago when the battery went bad. Would charge up and try to start but had an internal short that was a huge draw on alt when firing it up.

I was sure it was battery too...

But...

He borrowed a known good battery from me and says it does the same thing....

Maybe its a bad alt.....maybe he toasted it when he tried to jump it the first time or by using the previously flat battery with it...?

But cant check the alt the way it is without pulling it and taking it somewhere I guess...it only runs 3-4 seconds....LOL...but that may be my next suggestion to him

[shadango]

So we spent about 5 hours messing with it.  Alternator seems to be charging the battery fine when it runs.....no crazy spikes or anything.....runs at 13.85 to 13.95 ish the whole time its running....getting plenty of fuel....even tried dumping some gas in the the throttle body and no joy.

After many many cranks, and after looking at all the obvious stuff and then the not so obvious like IAC motor, TPS etc, and after many more cranks we got it to run.....through nothing we did.....it just started.   And ran 20+ minutes.

During that time that it ran, the gauges started working......and the odometer started working.....like magic....all looked right for a minute or so,.,....then "no bus" showed up on the odometer and it all went to hell again.....gauges stopped, all the lights stayed lit.

A neighbor (moapr mechanic for 25 years) said we should try swapping the CTM out for one he had.  So we shut off the engine and it took an hour or so to get the old CTM out (long story).. ....eventually swapped in the CTM that the neighbor had..... and same symptoms.  Took many many many cranks......
Eventually it would run again.

We found that it would restart immediately after shutting it down, so we tried swapping the CTMs a couple times and while it would restart, the dash light were all on and the gauges, tach etc did not work.

So I suggested that he let the truck sit overnight...assuming it does not start the very next time, I said to try using a heat gubn and heat up the PCM under the hood a bit and see what happens.

Wish there was an easy way to check the PCM!    I had my code reader.....no issues there.......though at one time we DID get a message that indicated no pwer to the PCM relay.......but only once...probably related to disconnecting and reconnecting the battery so many times...LOL

At wits end.....but hate to give up on the Mopar!

[CHL2T]

Does it have a chipped key? (security chip)
My buddies 2000 or whatever volswagon jetta does the exact thing you describe (gauges work though) if he doesn't have the broken off chipped portion of his key close to the ignition for five seconds after starting, It will simply die after five seconds

[shadango]

Does it have a chipped key? (security chip)
My buddies 2000 or whatever volswagon jetta does the exact thing you describe (gauges work though) if he doesn't have the broken off chipped portion of his key close to the ignition for five seconds after starting, It will simply die after five seconds

I dont think so......it will actually run at some point for 20+ minutes.......

[ShelbyDogg]

I had a similar problem with my GMC. Battery would always die because it would sit for months without using it. I bought a battery buddy to trip and disconnect if the battery got low but I could push a button then start it. On one of my resets the thing ran terrible and shifted funny. I'm thinking I reconnected the hot wire while the key was on and zapped the computer. Had to take it to the dealer and pay $760 to get it replaced and reprogrammed.

When he jumped it, he might have had the key on and blew something.

[barracuda7199]

The factory security system is tied to the power door locks in the doors. If I remember right is the passenger side that actually turns it on when you use the keyfob to lock the doors. There is a green wire on the central timer module behind the passenger side kick panel or the glovebox. It's been a while since I have done this but it's in one of the 2 places. You can splice into this green wire connect it to a good ground and it should bypass the system. If you unsure of the ground trick you can try it with a small fuse inline to protect the wiring.