Jeep tj ignition issues

brady99tj

Member
Joined
Nov 4, 2015
Location
salisbury
here recently my jeep has been forgetting its parameters everytime I cut it off, kinda like my battery is dying. So I've been holding it at idle and letting the computer catch up then everything is fine. It's doing this almost everytime I turn my key off and then crank it even though my battery isn't dieing. Now it has gotten to where it isn't reading my factory chipped key. The key light will flash then it cuts off. It doesn't do it everytime but sometimes it'll take a few tries to get it to work. I have a brand new battery, and sometimes its sluggish to start like something is draining my battery, I've tested my alternator and have good voltage coming out of it, it's also just a few months old. The only thing I can think of is the computer. Any insight will be appreciated.
 
I ve cleaned them, nice shiny metal connections.
 
Factory ends, the cable and end is all together.
 
Check voltage at the battery terminals, on the posts instead of on the clamps. That way you can measure the charging voltage that is actually getting to the battery. Also do the same measurement, but put the ground probe on the engine instead of the negative battery terminal. This will include any problems with grounding (ground connections) between the engine/alternator and the battery, so that's a more complete picture of what's happening.
You can also look at voltage drops while someone else is trying to crank the engine, which may be the only situation that matters in this case. You may have a starter issue or connection problem to the starter.

But yes, if you have one of those dumb transponder keys, those can cause problems as well. That needs to be fixed as well if it's not working, even though it's unlikely to cause the sluggish starting problems. You may have more than one problem here, or you may have a power connection problem that is causing the ignition security stuff to not work properly.
 
I feel like it's a power connection somewhere since the computer keeps forgetting the parameters and has to re read everyhing everytime I crank it.
 
But the battery isn't dieing, the sluggish starts were with the old battery the autozone tested said was bad a replaced it no questions asked
 
Your computer is losing memory, meaning it is losing power.
I'd started checking fuses. Isnt there a Retained Accesory Power or ECM fuse on a TJ?

@Jody Treadway can probably answer that in his sleep.

The battery terminal corrosion isn't a complete impossibility only because some corrosion could produce enough resistance to prevent current flow, but the starter inrush could bridge the resistance gap and get everything flowing again. That'd be a long shot. But in the realm of feasible.

But Id start at the ECM losing power and work backwards from there. Does the amount of power off time matter at all? IOW if its in closed loop and you shut it down and immediately restart does it still need to relearn?
 
Start with measuring TP sensor voltage key on, engine off. Then compare that to the voltage with the engine running at idle. My money is on a failing TPS causing erratic idle.
The SKIM key issue could be a weak key or failing SKIM module.
Also, safely unplug your air bag clock spring and see if either of the issues subsides. The clock spring and TP share some similar circuitry and a bad clock spring can cause TP- like idle concerns.
I don't see the two being intertwined necessarily but I've seen weirder.
 
I'll throw out it could be a weak starter with a few shorted windings causing ecm reset during starting but in that event probably wouldn't fire and die...

Edit.. Just reread Fabrik8s post and notice he covered possible starter issue.
 
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