Engine Light/Battery Light

[Yoboloko]

Two problems.

Engine light is always on. Mechanic checked it, the light went away for a few days, but came back and has stayed on ever since.

Tonight, after driving for 2-5 mins, battery light came on and stayed on. Stopped the engine, to put gas, drove for 2-5 mins and came on again.

Not sure if it's just me, but the engine has more "whine" to it. I'm guessing bad battery or alternator?

Anyway, I left it at the garage, and they'll take a look at it tomorrow morning.

Any ideas why the engine light always stays on? Bad sensor?

 

[JasonJ]

About 3,000 reasons why the engine light would be on.

Have to get the DTC out of it to know the general why.. even that doesn't always tell you specifically which part to replace. Without knowing the code that is set, no one knows anything. The garage should be telling you that information when they get to looking at it.

A failing alternator can make a whining noise... but that's just guessing based on so little information. You'd want the battery charged and tested, as well as the alternator checked out on and/or off the vehicle before you could tell too much.

 

[Yoboloko]

Mechanic checked it and said it's the alternator (which I suspected). I just recently changed the battery this year, still has a 5 year warranty on it. Alternator will come with a lifetime warranty. From past experiences I think the whine also comes from a faulty/dying alternator. He said the alternator is only holding 12v, as opossed to 14.3v, does that make sense?

For the engine light he said it's coming from the sensors on the exhaust. He said it either means the sensors simply need to be replaced, or the exhaust could be leaking.

 

[renegade 04]

The good denso alternator that the renegade has is capable of producing 15 volts. For a Chrysler vehicle like our jeeps you want the jeep to be charging around 13.8 to 14.3 volts.

 

[LibertyTC]

Would be nice to know the stored engine code#s. Sounds like 02 sensors, use NTK when you replace them.
Reality is the engine is not going to run correctly, with low voltage output.
Alt fail and pretty much running on left over battery power only, by the sounds of it.
When the battery light comes on, the VOM comes out! I leave one in the Jeep.
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The VOM may have some variances. ScanGage was reporting 14.9 at the same time.

 

[JasonJ]

"Holding 12v" means that the alternator is not outputting anything at all... that's just running on battery voltage.

Issue is, you need proper vehicle voltage to be sure that everything else electrical is working correctly, including the sensors in the exhaust (which really could only be referring to the oxygen sensors, but which ones?).

Any sensor can pop off a fault code for incorrect input voltage, turning the check engine light on.... doesn't mean the sensor is faulty and needs replacement however.

 

[HoosierJeeper]

Sounds like a bad alternator. My LR3's alternator just went bad and it whined, plus the intermittent battery light.

As for the CEL, could literally be anything from a transmission issue to a misfire to catalytic converter issue to a coolant temp issue to a fuel issue. With an 03, you can do the "key dance" to get the codes. Cycle the ignition off-on-off-on-off-on and it should give the codes in the odometer.

 

[Yoboloko]

Sounds like a bad alternator. My LR3's alternator just went bad and it whined, plus the intermittent battery light.

As for the CEL, could literally be anything from a transmission issue to a misfire to catalytic converter issue to a coolant temp issue to a fuel issue. With an 03, you can do the "key dance" to get the codes. Cycle the ignition off-on-off-on-off-on and it should give the codes in the odometer.

Cool, just learnt something new. Never knew of the "key dance" before, great trick to know. Right now, the mechanic erased the codes, so I'll wait for the new ones to come back (if they do).