Thread: BID 21 Fault Code - Discovery 4

Originally Posted by Gazza 01

Sometimes when I'm towing my caravan up hills the engine goes into limp mode. When I check the fault code with my Autophix OBD it comes up with "BID 21 Front Control switch". I clear the code but it can do it again. Seems that the Landrover Discovery 4 fault codes commence with PO --------. I can't find any info on BID 21 on the web- does anyone have any clues as to what the specific fault is as the stated fault of Front Control Switch is not very helpful.
Any help out there? Thanks

Either get a better code reader such as an IID Tool or take it to someone to read them. Your reader isn’t any used for a Disco.

Well this is the right place to learn Gazza, might take a wee while though.

As Disco suggested ,get a good Unit , perhaps $600 , but that will last you forever.

When towing, try using the sport mode /paddles and see what happens.

And welcome my friend 👍

I'm happy to read codes for you, what part of the city are you in ?

Originally Posted by DiscoJeffster

Either get a better code reader such as an IID Tool or take it to someone to read them. Your reader isn’t any used for a Disco.

Thanks for taking the time to reply. The Autophix reader I have is specifically set up for Landrover and cost just on $400 so it is not a cheap quality unit. It reads a large number of fault codes. I can't take it to my repair centre to read the code as I have to clear it to become mobile.
thx
Gazza 01

Thanks Hogarthdw and loanrangie for your replies.

Question to loanrangie- appreciate your offer to read the codes but unless the fault occurs again no fault codes will appear. For normal driving there is no problem and seems to occur at the start of a journey when towing even though I warm the car up before taking off

Originally Posted by Gazza 01

Thanks Hogarthdw and loanrangie for your replies.

Question to loanrangie- appreciate your offer to read the codes but unless the fault occurs again no fault codes will appear. For normal driving there is no problem and seems to occur at the start of a journey when towing even though I warm the car up before taking off

I think you will find that the ECU store faults that are not active or current, so with the right code reader you can see the issues that have happened even if they are not "current" issues. I suggest getting someone with a GAP IID tool to read the codes, take a look and compare with what your reader shows. You may be surprised at the difference a dedicated LR code reader makes to being able to sort out what is happening. The amount of info that I can see on the GAP tool for my LR is substantial.

The fault code was probably B1D21 and not related to why the engine went into limp mode. In this case it is possibly related to the audio system.



The GAP tool will capture all codes that will be present, including pending codes, as well as codes that may not be relevant but could have been logged around the same time.

Some code readers only capture the first logged code and can miss or not see all the others, but when you clear the fault the ECU’s clear all other faults logged at the same time.

Coincidently - had an engine fault code trigger today on the D3.

Checked fault codes and first code listed was B1D21-13 Remote Control Switch - General electrical failure and was listed under the Audio system ECU. Google search shows on later model LR’s this is sometimes called the Front Control Display Interface ECU.

So B1D21 is definitely the code you read and unrelated to your engine fault (as it was in my case today).