BMW N47 Diesel Fuel System Replacement

Another BMW 1 Series recovered to us not starting. Cranking over but engine not firing. Vehicle in the workshop on the diagnostics it was clear we had a fuel supply problem causing the engine not to start. On the live data we could see no high fuel pressure inside the rail, before going to the injectors. Suspecting high pressure fuel pump failure we removed the fuel rail to inspect for swarf – small metal parts inside the fuel system.
As expected swarf present in the system causing damage.

Once this occurs it is good practice to replace all components on the high pressure fuel system. Along with throughly cleaning the low fuel pressure side – fuel tank, lines and filter replacement.

Unfortunately new fuel system components would write this vehicle off being several thousands of pounds. However we have great suppliers of used parts (or green parts as they’re sugar coated as) that can supply us with complete used kits of the high pressure fuel system, with a 3 month warranty. Allowing us to repair at a fraction of the cost, keeping this car on the road

Alternative solutions to repair vehicles cost effectively.

Fault investigation and diagnosis

Used Engine ECU Cloning Replacement

An Engine ECU – DME/ DDE as BMW call it, monitor and control the running of the engine. Unfortunately these can fail for various reasons. Most common is water damage, however internal faults causing misfires, incorrect sensor readings, or even a non start. This means the ecu requires replacement.

A new unit is usually expensive in the thousands, which can write off some older vehicles. Buying a used unit, you cannot simply plug into the vehicle and expect it to start, as programming and immobiliser codes set in the software will prevent this from being possible.


Fortunately we have specialist software & equipment allowing us to ‘clone’ transfer the data inside the original unit into a used donor unit, thus allowing it to be compatible with the vehicle, enabling it to start and run like the original (without the previous running faults).

If your BMW or MINI is at the dealer with an eye watering sum to replace a component. Give us a call to see if we can help

Fault investigation and diagnosis


The FRM – Footwell module, fitted to various BMWs & MINIs between 2005 to 2015.

This unit controls the light and window functions on the vehicle.

A known problem with this unit is corruption of the data inside after the vehicle battery has been disconnected or connected to diagnostic equipment. Which then stops communication to the unit. The driver will notice no vehicle lighting or function of the power windows.

A few years ago the only solution was a new replacement unit at around £500, making it a costly repair.
However we have specialist software & equipment that allows us to repair the corrupted data of the original unit, saving the unit and more importantly money, at an hours labour of £72 inc vat. That’s more like it!

So if a garage has reported your FRM requires replacement, please get in touch, we will see if we can help!

BMW and Mini ECU repair

Water Damaged Engine ECU – Used Unit Replacement

We do enjoy replacing used engine control units – DME, here at Burch Motor Works. They are known to having a little bath in the box where they are located in the engine bay.

A new replacement for this ECU from BMW is £1,350 for the part alone.

The owner of this vehicle had tried other garages that are able to clone/ transfer the information from his old damaged ecu to a used donor unit. We also have the ability to do this.

However this is not always possible from the water damage making the file unreadable to transfer, as it was in this case.

Fortunately we have specialist programming equipment allowing us to transfer the ISN code, which is the immobiliser code from a used donor engine ecu to the immobiliser ecu – CAS. This needs to be done to allow the units to match for the engine to start and cannot be carried out by BMW dealer equipment.
Used engine ecu fitted and programmed, the car now starts and drives as it should! Along with drilling a hole in the bottom of the location box to prevent the same fault from reoccurring!

With the saving over £1,000 than a new ECU alone! That pleased the owner which pleases us too!
(Apologies for the poor quality screen shots)

ECU Replacement


BMW 320i Engine hesitation/ jerking under acceleration… fixed

A recent BMW 320i with the B48 4 cylinder petrol turbo engine with us. Fault of hesitation/ jerking sensation under acceleration. This car had been to a garage and bmw dealer previously but unable to locate the fault.

Road tested vehicle to confirm the fault under acceleration. Fault codes showing the engine is running too lean. Which means there is too much air going into the engine (or so it thinks) to fuel expected detected by the ecu using the various sensors fitted.

A fuel tank breather valve had been fitted previously by the bmw dealer, which is a known fault on this engine, but did not resolve the fault.

Using the bmw diagnostic system makes our job much easier to locate and rectify faults but it’s not always the silver bullet.

Using the diagnostics we ran through several air to fuel mixture tests. All passed ok but this is with the car stationary in the workshop. This fault only occurs whilst the engine is under load/ acceleration on the road. We then smoke leak tested the intake system, pipes, manifold, etc. No smoke present proving the intake system is tight and no allowing any extra air into the engine. Moving onto the turbo and exhaust and no smoke/ leaks either.
With the fault not showing in the workshop we took the computer on the road with us to inspect the live data readings to see if we can see any abnormalities to locate the fault.

Air mass, intake manifold and fuel pressure sensors showing plausible readings to the specified requirements. It took a while to locate as the fault was intermittent under acceleration. But eventually we found the oxygen sensor reading would go lean the same time as the hesitation/ jerking sensation. Upto 1.81.
Unfortunately the bmw diagnostics live data readings are not easy to read when they are changing quickly. So we grabbed the Bosch diagnostic system where we can graph and record the live data to easily read our findings.

The oxygen or known as a lambda sensor is located in the exhaust, either in the manifold or after the turbo if one is fitted. The sensor does what its called and measures the amount of oxygen present in the exhaust exiting the engine. A lean condition means not enough fuel so the ecu will then injector more fuel to compensate. Then a rich condition means too much fuel, the ecu will then inject less fuel. This is constantly monitored and adjusted to try to reach lambda 1. The ‘perfect’ air to fuel ratio.

As we could see from our sensor it would intermittently spike lean at 1.81. Rather than smoothly adjusting around lambda 1.
Next was to test the sensor & wiring directly, as an oxygen heater fault was also stored previously. All circuit tests passed ok. With the sensor removed we could visually see the engine/ exhaust gas is in a lean condition, with the sensor tip being white in colour.

With all other systems tested without fault to cause a lean condition. We suspected the sensor had an intermittent internal fault.
With the oxygen sensor replaced, vehicle software level updated & adaptations reset. We road tested the vehicle and it now drives as it should.
Tried. Tested. Fixed.

Fault Investigation – Diagnosis


Who is diagnosing the problem?

Source HEVRA:

There’s something of a misconception by some drivers, that the diagnosis of modern cars is done by a computer rather than a skilled individual. In fact, the computer (an essential part of the diagnostic process) just allows the technician to see things as the car sees them, and it’s down to the technician’s judgement, skill and further testing to get to the root cause, which then leads to a successful repair.

Let’s take an example of a modern vehicle, such as the Jaguar I-Pace.

If the car has a problem, a fault may have been recorded in one or more of the vehicle’s 41 addressable electronic control units (there are more than this if you consider those that don’t have their own diagnostic address).

There will generally be a number of fault codes, some that point to the cause of the problem, and some that are a consequence of the problem.

Let’s say we narrow down the fault to the Battery Energy Control Module (BECM). This ECU is capable of picking up 208 different errors.

Let’s say we have fault code P0ABF, Hybrid/EV Battery Pack Current Sensor “A” Circuit.

This fault has three possible definitions, so lets say we narrow it down to P0ABF-64, Hybrid/EV Battery Pack Current Sensor “A” Circuit- signal plausibility failure.

It’s now the technician’s job to find the root cause of the problem, so it’s out with the wiring diagram. The current sensor is located within the Battery Electrical Module, which has approximately 25 wires, all of which are red.


The current sensor itself is a control module of sorts, and although it doesn’t have its own diagnostic address, it communicates with the BECM using a controller area network. The connectors are gold plated for reliability, and pass through a ferrite core to reduce interference, before going through a connector, coming out a different colour, and finding their way back to the BECM.

The technicians needs to determine whether the fault is in the power supply, ground connection, network connections or the sensor itself. Furthermore, the fault could be a consequence of another problem- for example a partial short or a high resistance could lead to more or less current passing through the sensor than expected, in which case the fault could be somewhere else entirely. Equally, the software programming might not have allowed for the current draw of a particular circumstance, in which case the sensor may be reporting correctly and a software update may be required.

If you think this all sounds rather complicated, it’s the way of the modern vehicle, regardless of brand or even fuel type- those with combustion engines have similar levels of electronics, coupled with mechanical, thermal and fluid dynamics to consider as well.

Of course, it’s all in a day’s work for the skilled technicians in our network of garages, but hopefully this gives you some insight into why fault finding and diagnostics take the time they sometimes do and why cars can’t be diagnosed over the phone.

To ensure the best possible service to drivers, our member garages need to have a suitable qualification which ensures they know the principles and fundamentals of electric and hybrid vehicles. Our newsletters keep them up to date with new developments and allow them to gain experience from unusual problems repaired by others. Our unique vehicle-specific information means they can be familiar with a particular make and model the first time they see one, and if necessary all of our members also have access to our unlimited technical support should they need a second opinion or some help.

Used Control Unit Replacement and Brand Knowledge = Money Saving

This customers Mini came to us with a few strange faults after being parked up for a while over the lockdown. Both front windows not working, electric steering lock not working and various lights on the dash.

After plugging the vehicle into our Mini diag computer it was clear to see bizarrely we had separate faults for each item. Faults stored for both front window relays, so we thought we’d start here first to check/ fix the windows. After following steps, it located us to an internal fault with the relays within the FRM control unit. This unit controls the windows, lights and mirror functions. We removed to unit, removed outer cover to find a bit of moisture/ corrosion on the circuit board (suspect where it has been stood for a while). Carefully cleaned the board and refitted, hey-presto the front windows are now operational again. Sorted the first problem.

On to the electric steering lock not operating. When removing the key it should lock the steering, a clicking noise can be heard when operating, but nothing at the moment. Faults were stored for the CAS – steering lock road speed signal. Again following steps and with previous experience of this fault we saved a heap of time (and money). A known fault is a corroded wire under the battery tray between the CAS unit which is the vehicle immobiliser to the DSC/ ABS unit. The importance of this wire is providing a road speed signal to the CAS and steering lock. You don’t want the steering lock coming on whilst you’re driving along really!!

So we stripped the loom to find the corroded wire as suspected, repaired the damaged section. Refitted all parts and tested. Electric steering lock is now working again, great



However we still had warning lights on the dash and a CAS control unit – internal fault remaining, that would not clear. We suspect the corroded wires have short circuited the CAS unit. Only option is to replace the unit, unfortunately a new one from BMW/ Mini is £350, ouch! These units are special order from Germany only as they are made specific to each vehicle as it has the relevant immobiliser/ security information inside them from BMW/ Mini.

However we have various specialist tools and software at our disposal here. So we were able to purchase a used CAS unit for £15 (that’s more like it). Wipe the stored info off the purchased used unit, transfer the info from the old unit on our purchased used unit.
Fitted the used CAS unit on to the car. Cleared all the faults. No warning lights now present and car is returned working correctly

It must also be said the customer of this vehicle was extremely patient and grateful of us repairing the vehicle this way. Always nice to be appreciated. We are looking forward to seeing it again for regular MOTs and servicing

If you want your BMW & Mini repairing correctly at the fraction of the cost of the dealership. Give us a call on 01425 277800
(Sorry for the poor quality photos, we’re better at fixing cars than pretty pictures)

Recent Mini Cooper Petrol recovered to us

Symptoms of engine light on and engine cutting out at idle. Car had already been ‘quickly plugged in elsewhere’ with Camshaft Sensor faults.

Carried out short road test, engine light on with poor low idle. Vehicle diagnostic test showed no camshaft sensor faults but Vanos actuator movement on inlet & exhaust (the last place we’re close I guess ?‍♂️). If you don’t know what Vanos is and would like to know more please read this –

First step on these is to check oil is present in the engine. Near maximum on this as customer knows of the high oil consumption on these engines and tops up regularly, so that’s not the cause.

Next removed both Vanos Solenoid valves to check the strainers fitted to them for soiling, and hey presto nearly blocked solid. Restricting the oil flow to Vanos Camshaft Hubs which move from oil flow/ pressure.

Cleaned both strainers, refitted and carried out engine vanos adaptation test. Both values nearly bang in the middle, which is a good sign of healthy vanos solenoids, camshaft hubs and timing chain. Cleared all faults.

Road tested vehicle from cold to hot twice (once following day). Now driving as it should with no faults stored.
Nice simple known fault rectified within one hour of our investigation price of only £49 inc vat. With no parts needing replacement.
More times than not it’s cheaper to take your pride and joy to the people who know what they’re doing first time round! If you’re having troubles… you know who to call ?

Find out more about our fault diagnosis services