Hey all,

Been having intermittent issues on my 2005 LR3

Last week, had an episode, suddenly while driving having multiple lights go off (abs, suspension) and a loud fan noise. Drove the car home and had several codes to do with shorts.

Car restarted fine without the lights. The loud fan persisted a bit but went away on its own.

All codes have cleared except:B1C57-14 (2F) Passive start ignition relay coil circuit - General electrical failure - circuit short to ground or open

I have since also gotten the “transmission fault, traction reduced error”. I have the rear locker and this has happened a few times recently and has always cleared with rear diff calibration with the GAP tool

Battery is a 2 month old AGM interstate. I have checked the battery voltage right after the incident and it was 12.3. Voltage with engine running is a consistent 14.1. I have recharged the battery and it’s held a charge since the incident. I’ve checked for a parasitic draw and absolutely no draw (zero amps after about 20 minutes when it’s goes asleep)

Any thoughts?

 

Did you check the battery ground cable that goes to the ground lug on the fender behind the battery? I may look good but be corroded on the inside. Is the main fuze on the positive battery cable discolored? Sometimes a discolored fuze causes problems. This sound like a classic voltage problem caused by a bad ground. What is the battery voltage between the battery positive and the ground lugs under the air filter box? There is another ground behind the right front inner fender cover that sometimes causes a problem. try testing voltage from that ground lug to your battery positive to see what you get. What is the voltage while the engine is running at these locations?

Jeff

 

I’m not getting any voltage drop across either battery terminal (did clean negative prior to testing this yesterday). I’m getting 0.03 V going from positive terminal to fuse box while running but nothing while not running.

I’’m having trouble locating where the negative and positive cables go and the grounds for the negative go. Ran completely fine on a 2 hour drive today.

 

Sounds like a bad alternator or lose battery connection.

 

Wouldn’t I get a low voltage reading while running or a parasitic drain when it’s off (with a bad diode) if it’s the alternator. I’m half tempted to replace it anyway….

 

How exactly are you measuring voltage? If you are just taking a reading at idle, it means little. You pretty much need an analog meter or sorts to watch voltage while driving. Digital ones can be too slow to properly read short drops. The biggest clue to there being a voltage issue is the viscus fan. Power is required to pull back other clutch. So failsafe mode is full clutch. And its the first item that the computer will pull power from when there is an issue. Then the list goes onto heated seats, defrost system, air suspension, etc, etc. Basically the truck does have a setup where systems are killed in lower power states to keep the truck running.

 

This very helpful. I have been measuring with a multimeter while running in the garage. I also have one of those cigarette lighter voltmeters which correlates well with my voltmeter readings. Unfortunately, when the big incident with multiple lights and codes happened with the loud fan, I was going up an on ramp in a highway and was focused on driving and did not think to look at my voltmeter.

I have been watching this cigarette lighter voltmeter the past couple days since it happened and its running steady at 13.9 to 14.1 after it warms up (goes up to 14.3 at start times).

 

So you had an issue during a high-rev event? Have to tried to repeat that? Also like I said, those volt meters are not super accurate/reliable as they tend to average things too much. But its something! So keep testing. Overall your voltage readings certainly look fine. Maybe check out the main fuse inside the box at the positive terminal. They can crack/go bad without blowing. So you end up with annoying issues that are hard to pin-point. Mine had some corrosion I had to clean up.

 

Well, minor update

Found the negative cable ground point behind the fuse box. Measuring same as battery terminals 12.6 off and 14.1 on, no voltage drop.

Vehicle drove fine all day. I did have another 8 codes pop up just today mostly low signal readings and some battery short and audio system short codes. Different codes than before. Main fuse “looks” good as does the negative ground attachment point.

Alternator belt looks good, tight/not slipping.

I’m half tempted to just replace main fuse and then alternator followed by positive cable.

Or take it in…….

I just know a short or bad alternator can leave you with a car that won’t run very quickly.

 

So it happened right before I turned, I was first to turn left onto the on ramp and couldn’t do anything but go on. It was not during a high rpm situation but I think for sure it’s a problem that is happening only under load.