Land Rover Discovery 2 - Alarm and Transmission Mode Lights Flashing ("Limp Mode") Fix

Quick diagnosis and fix for a common issue for Discovery 2. When trying to start, sometimes the anti-theft system would trigger and disable the vehicle. If the vehicle did start (with or without a jump) the transmission mode lights (M and S) flash.
When the transmission mode lights flash, when it’s in drive, the shift indicator will flash. The vehicle will only go forward in 3rd gear and you’ll notice sluggish starts and high RPM at higher speeds. The transmission ECM usually triggers this type of warning light.
Here's the link to the battery pack. I ALWAYS keep one of these in every car, especially the Disco. Nothing's worse than driving on the beach, tides coming in, and the battery is dead!
amzn.to/3AxPJ9e
Disclaimer: The above link is an affiliate link; I do get commissions on sales through that link.

[@jimmydemoret]

It worked! The battery was $220 in 2023 US dollars and it fixed it!

[@NCRover]

Glad it worked! The transmission is finicky with low start up voltage. I think I have a slight parasitic draw, I drive mine maybe once a month. Usually the M&S comes on (even with the new battery). But if I let it idle, turn it off and back on, no more issue. I will say; it can also be the XYZ Switch, I have fiddles with that but I hear it’s not too bad to change and/or tighten. Some even carry spares just incase!

[@Mrvzla1]

Check the tensors for alternator!

[@jimmydemoret]

You = the man! My battery is old and has gotten weak and I have this issue. Thank you!

[@NCRover]

No problem, glad it helped.

[@nolo1337]

Ty this helps morons at walmart stuck me with a 650 cca 😤

[@NCRover]

Thanks for watching and glad it helped. You can't really have too many CCA. There are 3 important factors: 1) will the battery fit in the space under the hood 2) Does you wiring connect to the post 3) Does it meet the MINIMUM CCA Like you see, with these older Disco's, low amperage at ignition can cause all kinds of issues; which is why I went with a higher CCA. These Costco batteries are really fantastic for the price and warranty.

[@garyallen4486]

Volatage needs a boost. Rev up when starting the engine

[@NCRover]

Unfortunately the battery was end of life. It was at least 10 years old. But yes, voltage boost would prevent the issue if you’re in the field or just have a weak battery due to the car sitting a while.

[@valerieogeda3204]

What does the M and S mean? Was it the battery needing to be replaced like you mentioned?

[@NCRover]

There is a "mode" button on the shifter. Normally, when you push the mode button, you can select "Sport" (the S lights up) or "Manual" (the M lights up). "Limp Mode" is when there is an issue that throws a code in the transmission control module; when this happens both the S and M will light up at the same time. Also, the disco will ONLY run in third gear. You'll notice it is sluggish to start, and runs very high RPMs. Various issues can cause the car to go in to limp mode. For me, the low battery voltage was causing an amp surge that was throwing a fault in the transmission control. When it senses the surge, it protected itself by going into limp mode. So in my case, the battery was the issue. There are other situations that will cause both the S and M to light up.

[@Mrvzla1]

Link where you bought the jump starter? I like digital meter!

[@NCRover]

I added a link to the description, thanks for watching