LR3 p0560 mystery

Haywood

Member
May 10, 2016
8
0
San Diego
My 2005 LR3 4.4 has finally stumped me, and I need some expert help solving this one. Car is running great, but the check engine light is still lit.

Background- On a quick errand trip I saw the battery light come on mid way. When I got back in the car to leave, it was gone, with no other/new warning lights. A few days later, the check engine light comes on, and the Torque app is telling me it's p0560, System voltage error.
So I do some checking with the multimeter. Battery getting 14.4 to it while running, about 12.7 with the car off.

So I check the fuses for the ALT, nothing. I check the ground cable from the battery, no it's looks great and both terminals are tight. I decide to see what the NAV screen says, so I check the 753 diagnostic screen and it's is showing 13.5v while running, and no DTC codes.

20201108_153630.jpg
20201108_153719.jpg

I finally jump on the internet and get led in a few possible directions by reading other people's posts and start to throw a few parts at the problem. Hoping it was something straight forward and since the truck has 175k miles and what looks like the original alternator, I started there.

Here is what I've done so far, to no avail-
New Denso 150a Alt
New H8 900cca battery
New brake light switch at the brake pedal
Checked the few grounds I could find
Checked fuses
Check wiring in passenger door sill (what a pain)
Check 3 wire plug going to Alt, unplugged and replugged back in to be sure.
Checked both the ECU and TCU behind battery by unplugging and looking for possible corrosion, both looked fine at the pins

Now I'm starting to think this could be something dumb/minor, that I am overlooking.

20201223_141722.jpg
Screenshot_20201108-153615_Torque.jpg


20201223_142019.jpg



I do not own a Gap tool, but I am considering it if it will provide me a lot more info than the Torque app does. Would appreciate any insight to anything you think I might have overlooked in troubleshooting this, thanks!

Mark
 
Last edited:

discostew

Well-known member
Sep 14, 2010
5,942
342
Northern Illinois
I think your alternator is failing. That's about the only thing I've seen cause the battery light to come on.
The propper way to check that charging system is to watch the duty cycle being commanded and the actual output of the alternator. As the duty cycle starts to climb up over 70% or so that alternator is being asked to step it up a little bit by the ECM. Normally I think the duty cycle should be around 25% if the alternator is optimal.
There is a ground strap that goes from the body, the right motor mount, to the frame. But usually you get a no start, just a click from the starter kind of thing. I mention it because I know a guy who calls that the charging system strap. He must have had a bad experience with that thing and charging system faults.
 
  • Like
Reactions: globalwad

nickhand

Active member
Jan 18, 2018
25
1
Oklahoma
clean the posts check breather tubes how old is the battery,
Here is what I've done so far, to no avail-
New Denso 150a Alt
New H8 900cca battery
New brake light switch at the brake pedal
Checked the few grounds I could find
Checked fuses
Check wiring in passenger door sill (what a pain)
Check 3 wire plug going to Alt, unplugged and replugged back in to be sure.
Checked both the ECU and TCU behind battery by unplugging and looking for possible corrosion, both looked fine at the pins
 
  • Like
Reactions: globalwad

Howski

Well-known member
Oct 19, 2009
1,164
80
Greenville, S.C.
Have you looked at the battery cables themselves? At least something else to eliminate. I’ve seen examples of the negative ground going bad on LR3’s
 
  • Like
Reactions: globalwad

Haywood

Member
May 10, 2016
8
0
San Diego
Yeah I did. I actually removed the negative cable and it looks new. I finally gave up and it's at the dealer right now for a diagnosis , but they aren't having much luck finding the cause either. Weird