1991 ECM code 46 and battery looks bad

Like the title says, I've got an overvoltage condition.

Hard wheeling this past weekend, sunk in water (but engine kept running).
Jump started another Jeep a couple of times.
Smoked my electric winch.

In that order.

My XJ ran fine until the winch smoked.
Codes says 46, overvoltage.
Meter goes ALL the way up unless I have everything running, lights, AC, fan, radio, etc.

At idle, the voltage drops below normal.

I checked for short and open circuits with an ohmeter at the alternator and did not find any.

I will swap the alternator this weekend (I have a spare).

I also got the code 27 and limp mode driving home at 15 mph.

I reset the ECM which cleared the 27 code and the battery disconnected code 12 ( which I caused when swapping out the leaking battery).

So I do not think the ECM is broke.

What do you folks think?

1991 XJ Laredo
Automatic
4.0L
no engine mods
Picture of the shallow water...

I thought NJ was a toxic wasteland--where did all of that green stuff come from?

Just kidding--however, NY is completely paved over the entire state!

I wouldn't drive it overcharging--some mighty expensive electronics there.

Could just be water/mud in the alternator--don't you just love it being mounted so low? I would swap the alternator and check all of the harness connections in the engine compartment for contamination.

Good luck.

An update.
I picked up a used ECM at my local junkyard for $20 and it changed the failure symptoms.
This leads me to believe my ECM was bad and the JY ECM also was bad.
I had already swapped the alternator and battery with spares.
The XJ must have been in limp mode or just broke because gas was pouring out the exhaust.
No injectors are stuck open, the fuel rail pressure stay up for hours after switching off.
I also hot wired the shutdown relay and fuel pump relay.

So, I most likely will look for a refurbished ECM with warranty as a next step.

dennis461 said:

An update.
I picked up a used ECM at my local junkyard for $20 and it changed the failure symptoms.
This leads me to believe my ECM was bad and the JY ECM also was bad.
I had already swapped the alternator and battery with spares.
The XJ must have been in limp mode or just broke because gas was pouring out the exhaust.
No injectors are stuck open, the fuel rail pressure stay up for hours after switching off.
I also hot wired the shutdown relay and fuel pump relay.

So, I most likely will look for a refurbished ECM with warranty as a next step.

Click to expand...

The ASD relay functions off pin/cavity 51 (FSM 95) of the PCM. If you are having to hot wire the ASD relay I think you have a harness/PCM issue--you have swapped the PCM, kind of reduces the odds of a bad PCM, but not unheard of.

I still think you need to clean connections and test, but good luck and post up what the reman PCM gets you.

Still not running:confused1
Have tried two used ECU (PCMs) with part number 56027488.
They both behave the same, cranks, fires, shuts down in about 3 seconds.
Put my old one back in and it starts, runs, and dumps raw gas out the tailpipe, while overchargng the battery.

My simple checks of sensors don't show any problems.
I guess I'll be checking for a timing problem next with the distributor and TDC.

Well, here is another update. :spin1:
I bought two used ECM's, both claimed to be good for 1991-1992, as most parts stores list them that way also.
Both had part number 56027488.
One I pulled myself from a 1992 model.
Neither would allow the engine to run more than a couple of seconds.

I bought a third used one from a person who took it out of a 1991.
Part number 56027528.

Jeep started up, idled fine and rev's up nicely. Battery voltage is correct also. Test drive this weekend, gotta ht that water hole one more time:doh:.

dennis461 said:

Test drive this weekend, gotta ht that water hole one more time:doh:.

Click to expand...

DUDE, don't do it, man! LOL!