Forgive me in advance because I am not a car expert. I have a used 120K+ miles 2014 Land Rover LR4 that runs awesome like 7 months out of the year, but when the temperatures start to climb above 50 degrees, I run into an issue where the dashboard lights up and everything faults. Stability control fault, transmission fault, low fuel warning, lowered suspension, HDC fault, special programs off, etc. Sometimes it goes into limp mode, sometimes it doesn't. Sometimes if I pull over and shut it off, it resets itself completely and sometimes it keeps the check engine light on. If I don’t shut the car off and it goes into limp mode, won’t accelerate and then all of a sudden it jerks and starts to pick-up speed again, but it doesn’t downshift like it should. I had it looked at by the dealer when this happened for the first time a few weeks after I got it and they said the battery connection was loose; they hooked it back up, it ran fine for basically a year. Next summer rolls around and the problem comes back, but this time it's more frequent and the car isn't recovering as well - going into limp mode more often in the middle of highways and what not. Its now my third summer with the car and the problem is still unresolved and seems to be worse still. My dad is a mechanical engineer by trade and pretty well versed in cars, but even he's stumped. So far, we have:

1. Checked grounds and replaced a couple of wires/connections
2. Replaced the alternator and fixed the sense wire
3. Replaced the battery and the sense module
4. Replaced fuses
5. Tried disconnecting the ABS module
6. Replaced the ECM

But to no avail.

Right now, it’s with a local independent Land Rover shop and has been there for about two weeks. No word as of yet. I’m feeling extremely discouraged at trying to chase what feels like an unidentifiable problem at this point, and I also don’t want to dump money into chasing solutions that are just going to set me back financially; but I can’t NOT try to figure out what the hell is going on.

Please, if anyone has any more suggestions, I am desperate to fix this car and hopefully put this all to bed.

 

Do you have a way to read the codes? If so, post them up here.

What region of the country are you in? Can’t think of why temps would affect it, but does it maybe coincide with the rainy season where you are? Roof drains leaking into the passenger footwell (and central junction box) is a known issue and can cause this sort of thing.

Most of these warnings seem to occur together frequently, and can have a number of causes. Low voltage is clearly one, but I’ve seen reports on these forums of brake pedal switch failure, transmission control module, throttle position sensor, and wheel speed sensor create this type of havoc. One person even had rodent damage in the large bundle of wires behind the battery box (leads to the central junction box).

However, the low fuel warning is a bit strange, and makes me think this is a wiring/canbus issue rather than a hardware issue with one of your sensors. I would start with a readout of the codes, but also maybe check for signs of past moisture in that passenger side footwell area.

 

Have you tried replacing the brake light switch? That can cause all sorts of problems on the LR3, not sure if it applies to the LR4.

Found a post with similar issues for an LR3 so I'm not sure if it applies but this may give you some other places to look. Some have mentioned the transfer case / transmission control unit under the battery having corrosion or generally being bad. Other's have mentioned a broken/loose broken ground wire located behind the driver’s side (LHD, left side) lower trim panel.

Hope that helps.