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Fault Code 41

Tom R.

NAXJA Forum User
Yesterday I tried to start my XJ and the battery was nearly dead. It was a miracle that I even got it to start. The check engine light was on, so I pulled the codes. I got a fault code 41, which is bad/faulty/incorrect switching.....I'm assuming the alternator isn't switching correctly.

Funny thing is the problem didn't come back after I drove around. This makes me wonder is there's an intermittent short somewhere causing my battery to drain and storing the fault code 41. Has anyone ever had this code? Is it possible the alternator is intermittently bad? I'd think an alternator is either bad or good, but not having problem intermittently. Any help is appreciated.

You don't mention the year, motor, tranny, or xcase involved and it's not in your profile. It would definitely help!
An alternator or its connections might be intermittently bad, especially if it's got a lot of miles on it. When the brushes start to wear out, they will occasionally lose contact and then reestablish it. The first thing I'd do, though, is check all the connectors, battery terminals, etc. to make sure it isn't just a simple bit of corrosion somewhere.
Oh yeah, I forgot to list the leading particulars...

'92, 4.0L, and for giggles......auto tranny, 231.

All the connections are tight, but I'll check again just to ensure I didn't overlook anything. I received a T/shooting tip today that I never heard before. What do you make of this?

Make sure all accessories are off (including disconnecting radio or any other item that may be drawing power even when the motor is off). Next, disconnect the neg cable from the battery and connect a test light between the cable and the neg battery post. If it lights then it means something is drawing juice. Pull each relay, switch, etc., one at a time and when the test light goes out you have the culprit. From what I understand it's often a relay or other electrical item that's making contact when it shouldn't. Thanks,

That tip is for checking why a known GOOD charging system has a battery go flat.
You probably need a new alternator,have it checked for output.Lots of the auto parts stores can do it for you.
low voltage will throw funny codes. i would guess that you have an offdraw or a weak battery that is still accepting a shallow charge.