The car from UK. Rebuilding

As we know, in the UK (and in some other countries), the car movement happens on the “wrong” side of the road. If the owner of the vehicle wants to use the car in countries, where we drive on the right side of the road for the long term, the rebuilding has to be performed.

I’ve seen many advertisements, offering “high-quality rebuild”, but none – “we will break your car”.


In this entry about the situation, when the rebuilding was performed by “professionals”.

Regarding rebuilding of mechanical things, I will not comment – there is not enough information. I was asked to help to solve electronic problems.


Initially, after rebuilding all windows were opening “wrongly”, also door icons in KOMBI – inappropriate. It all has to be redone – that was already performed before I took part. SRS system – amputated. In addition with NCS all airbags were uncoded, also the wires to airbags have been destroyed and “false plugs” were installed. Obviously, several “specialists” one after others have worked on this car.


During the last two years, the car has spent more time on services than driving. None of the many specialists couldn’t solve the problem, unfortunately. DME has been opened and after glued with silicone – obviously, someone of the “specialists” was thinking, that it was one to blame.


In DME error message memory regularly the error message regarding wide band trim is (was) recorded. The owner has replaced 2 probes (he was using only Bosch/OEM), but without results. I tested both used (and “damaged”) probes – they were in excellent technical order.

The error message regarding the accelerator pedal was appearing regularly. Replacing the pedal module (2 times) was without results.

Unfortunately, the car couldn’t pass TI – the exhaust gasses overreached the norm.


It’s not hard to understand the direct expenses of the owner of the car have reached 4-digit number, in addition – without success.


I assume, that the readers of my blog have read descriptions regarding resistance of Nernst probes (what they are and what they define), so I will just slightly touch this part.


Problem with Lambda probes: opening ../F5/F2/F6, we see both wideband and control probe have serious problems. In addition, the control probe has a critical situation. Nernst resistance: above 35000 Ohm (correct parameter: 100 times less). So: the probe has very, very bad chemical efficiency.

Logically – its voltage is insufficient, the trim procedure of the wideband probe was unsuccessful. As a result – the appropriate error message about unsuccessful trim of wideband probe is recorded. It is NOT an error, that exactly the wideband probe is damaged! Unfortunately, all specialists have been in the same meaning – exactly the wideband probe has to be replaced. As I already mentioned before, it was done for two times, but without any results.

Also, the efficiency of the wideband probe decreases, in the picture – best scenario. Typically: 1500 .. 2000 Ohm (7 .. 10 times above norm). One more interesting symptom – when DME starts to heat the narrowband probe, the Nernst resistance of the wideband probe increases to 7000 .. 9000 Ohm. Obviously, the probes are somehow connected! How is that possible? It is more than strange!


First assumption – damaged control probe?

Replacing the control probe (with used OEM probe – for test) – nothing changed.


We start a more serious exploration of the problem.

Here, how the measurements were performed:

One technician was below the car – in the hole. The other was watching live data of INPA and data of oscilloscope.


Here, heating of the control probe, by DME plug:

How do you like such a signal?

Ground – with “waves” of around 2 V, but with “notches” of +12 V. What can cause such notches? Low-quality power supply! Ground waves, instead – by incorrectly performed grounding.

Here, the heating of the probe, measurements performed directly in the plug of the probe. Reminds something like this:

As we see, Ground waves are gone, but +12 V look’s more than strange! Without options – the power supply of the probe is connected completely incorrectly. Obviously, the wrong place of connection for power supply has been chosen, too thin wires are used.


It’s clear such power supply can cause heating problems (the chemical efficiency will be 20 .. 30 .. 40 % lower than optimal), but not 100 times increased Nernst resistance! There should be other causes!


Continuing the exploration, things became more interesting.

INPA live data says: the fuel mixture is very rich (Lambda around 0.9), because of the trim procedure of wideband probe has failed for numerous time, but the wideband probe voltage is only around 0.5 V.

In the same time oscilloscope (measurement in the plug of the probe) indicates:

the voltage is not 0.5 V, but 0.85 V! So – the data are correct! Obviously, the problem is in connection “probe – DME”.


When moving the wire “clew”, suddenly the Nernst resistance of the control probe started to drop swiftly:

Here, now already only around 3000 Ohm!


And, what is more interesting – the fuel mixture has become slightly lean, the voltage of the control probe – more close to correct!

And, which is not negligible – in the shape of signal we already see the moments, when DME measures Nernst resistance:

Cause of the problem is clear – obviously, the rebuild was done with “very high quality”. There are no other options – everything has to be opened…


Here, how the rebuild looks – wires change color in random sequence, the textile insulation tape instead of thermocouple has been used:

Continuing the exploration…

Wire, which is held by the master: power supply to Lambda probes. Appropriate crosssection: 2.5 mm2. From its “new” wire set “additions” ar “branching”. Crossection of the wire? What is that? Obviously, the persons who performed rebuilding, didn’t hear what is that. In this case – probes are “grounding” each other, it means the power supplies interact one with other. At the moment, when DME starts heating of control probe, the heating voltage for the wideband probe decreases – its chemical efficiency is decreased. In addition, due to this unexpected interaction, DME cannot adapt the heating maps of the probes! Choosing the wrong piece of wire – a chain of fundamental problems guaranteed!

The second nuance, which “installators” have not taken in account – in OEM solution, each probe has its OWN, independent power supply wire! Not knowing, why this is done – they simply used one common wire. Such, as if small nuance, fundamentally changed everything!


Here, the schematics:

As you see, EACH probe has its own power supply wire (in orange color)!


In addition, the “specialists” have not even had any idea, why some wires are coiled by two! Why don’t bother themselves, coiling the? At this moment, it becomes very clear, why there are error messages regarding CAN communication…


Here – wires are not soldered, but simply coiled!


The only possible solution to the problem: complete replacement of the wireset, using parts from a donor. Sufficiently laborious event. In addition, it has to be done only because the initial rebuild was done by complete fools!

Restoring of SRS (airbags, pyro-patrons, encoding of SRS module) – it’s also ahead.

Hopefully, the replacement of the wireset will solve the problem with accelerator pedal – also its prevention still has to be done.


The worst thing is surprises can appear in any module (every sensor, connection of the executing mechanism, any switch), which was touched by the “specialists”!


After 24 hours. The same car, the same probes. After replacement of the wireset:

Here – all problems with both Lambda probes solved as they never existed!


48 hours later. Car “lost” the electrical fan. Cause – prolonged and unsolded (only coiled) wire.

72 hours later. Active steering and steer angle sensor failed.

And how many surprises they still will appear…