The P38 Range Rover Body Electronic Control Module, as many people know all to well, is the large control unit that sits under the drivers seat and controls the majority of electrical circuits on a P38 Range Rover. It was fitted from 1995-2001
The Becm can cause no end of problems when tackling issues with a P38 Range Rover. It is difficult to Diagnose if the Becm itself is causing a fault or whether it is the wiring or a component failure, causing the Becm to malfunction. The Becm has no Fault Diagnosis as such and to make things difficult the most important information in it is locked. This prevents us from fitting a second hand unit to replace a faulty one or using a donor one for testing.
Be very careful when trying a second hand unit in your Range Rover, it can cause the instrument cluster to show a higher mileage. The Becm verifies its own mileage against the instrument cluster. The highest mileage is then synchronised between them both. If this has already happened send your instrument cluster along with the Becm and it can be rectified.
Below is a selection of faults often experienced with the Becm
Electric Window Failure
Engine Will not Crank
Key Code Lockout
Fuse Failure Warning
No Instrument Cluster Display
Electrical Fault Warning
Central Locking Failure
Incorrect Mileage showing
*Transfer - Neutral Lock
Rear Wiper Inop
Wing Mirrors inop
Seat Electrics failure
No Cruise Control
Air Suspension Faults
Remote Key inop
No Selector Lever Display
* If Display shows Select Neutral : Ensure fuse 11 of the Becm is not installed
If you have problems with your Range rover and you don't know whether it is the Fuse box, Becm or wiring then easiest thing to do is send your Becm, Engine Ecu and at least 1 working key to be tested.
1st your Becm will be unlocked and any coding issues will be corrected. It will then undergo a extensive test of every single function.
The 2nd stage is the sleep test to ensure your Becm sleeps within the correct time and draws the correct amount of current. This will ensure you Range rover will not suffer battery drain.
The 3rd test involves putting the becm in a central locked state and recording its outputs for up to 12 hours. This will detect voltage fluctuations, serial data bus faults, Central locking faults and false triggers to the Alarm and immobiliser.
The 4th part involves putting the Becm into Key Code Lock Out and recovering it with the EKA code stored within you Becm. This ensures not only that the data is correct but also that the Central locking control circuity is working correctly.
The next stage is testing the security Link between the Becm and Engine Ecu, to ensure your Range rover will start and run.
Finally when both the Becm and Engine Ecu pass all the tests the key fob is next to receive some attention. The Batteries, Buttons and Battery cover are replaced if needed.
If the Becm is found to be OK then wiring diagrams and instructions will be sent back with your unit indicating which circuit/s on your range rover are at fault. The diagrams will enable you to quickly locate and rectify the fault returning you problematic Range Rover back to perfect health.
This is also applicable if your Becm has been repaired. You can prevent a situation were it can be blown on re connection because the existing fault hasn't been rectified.
Why do I need to send the Engine Ecu and Key:
The reason for sending the Engine Ecu and a Key is for the Security and programming. The Becm, Engine Ecu and Key are all security matched. When all three are connected up, as they would be on the vehicle, every function can be tested. The security codes can also be checked and matched if need be. when you receive your units back you can just plug them straight in without the need for programming.