This entry is a part of N46 engine repair. I put this problem separately, because this case clearly shows, how important is to perform quality diagnostics. Only after correct diagnostics, the repair can follow.


Shortly about the problem. E90 with the N46 engine, already after one year after purchase of new vehicle EML indicator regularly lighted up in the KOMBI, the engine reduced power. Dealer service performed diagnostics, stated, that the problem is in throttle. It was replaced, the situation didn’t get better. After the end of warranty, the customer replaced the throttle (at his own expenses) twice. Unfortunately, the EML indicator continued to light up regularly, DME repeatedly recorded the appropriate error message.

Last versions of “specialists”- DME and all wireset had to be replaced.


When connecting INPA, I stated, that the error messages regarding throttle sensor indications and reference position are recorded. All data in the error messages for both sensors were identical (0.32V; 0.46V).

Obviously, the indications of at least one of the sensors are incorrect (because both sensors are creating a cross curve, their values have to correspond in only one pint: 2.5V). It’s clear, that at first, the problem with sensor readings has to be solved – it’s a basic thing.

For this engine, in case of throttle problems, ISTA offers to perform voltage measurement for one of the sensors in one static position in one point! Absolutely useless test: an indication of the static position of one sensor doesn’t give the real picture! Even more – not INPA, nor ISTA don’t show live data regarding both sensors.

Accordingly – the measurements of the sensors have to be performed with a multimeter or oscilloscope.


In the image: connection of throttle


Throttle test:

  • disconnect corrugated rubber tube to the throttle, to open and close the throttle mechanically;
  • turn on the ignition, connect at first to Pin 1 and then to Pin 4 (accordingly: first and second sensor);
  • open and close the throttle, make sure, that the indications of throttle sensors correspond to required.

The cause of the problem was detected immediately: a signal of the 1-st sensor (Pin 1) disappeared regularly! Obviously, the problem was of a mechanical nature, because the problem disappeared, moving the connector of the sensor.


The connection of the wire to the connector was checked, disassembling the connector. It was correct.

Checking the resistance between Pin 1 and Pin 2 (power supply), I made sure, that the connection of the throttle sensor by the connector is not damaged. Obviously, the problem is in the connector itself.


It’s interesting, that I was the first one, who connected to throttle wires – obviously, none of the previous “specialists” didn’t consider it as necessary. Say – the error messages are regarding throttle – let’s change throttle.


New connectors were ordered from BMW AG (they were delivered with attached wires of ~20 cm length). I replaced the connector, deleted the error messages, checked performance of the throttle. The problem was gone.

I performed the inspection of damaged Pin 1 in microscope:


Conclusion: two of four elastic plates (on the left side) are damaged – they are folded. It’s clearly visible, that between this plate there is an opening – it not supposed to be like that.

It’s not possible to define anymore if the connector was damaged when improperly putting on the throttle connector or by some other reasons.

Most significant: qualified diagnostics took around 10 minutes. Replacement of the connector: 10 minutes. Diagnostics check (after repair): 10 minutes. Costs of the spare part: several EUR.

According to the customer, one of the “specialists” has worked on the problem (without results) full working day; the car was left by the more real several times for several days. It’s clear, that replacement and three throttles itself cost to customer several hundred EUR. Moreover – without any progress. Although the damaged part was a connector, worth several EUR…

In the image: after-repair check-out with oscilloscope Micsig. 28M points memory, Mega Zoom, Infi-Vision allowed to make sure, that the signals of sensors are correct, their values are not faulty for even a million part of the second.

This time, unfortunately, I don’t see any excuse of unsuccessful diagnostics of previous “specialist” – the information and description regarding the performance of throttle from BMW AG is widely available, the structure and principle of the performance of throttle – very simple.


Related entries:

N series. Throttle and accelerator pedal