logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Correct Supply Voltage for Shaft Position Sensor in AUDI A6 C6 3.0 tdi BMK

koszynek 18738 14
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #1 16641901
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    Hello, I have a question about the supply of shaft sensor in the above described model. From what I measured it reaches 2.54 v. A request for a hint as to the correct supply voltage for this sensor. The sensor, of course, replaced, the fault still active is manifested by a difficulty in starting the engine. Regards.
  • ADVERTISEMENT
  • #2 16642145
    paszczakq
    Level 27  
    Posts: 1011
    Help: 48
    Rate: 202
    Or maybe this invention on 4-5 chains (timing) has already reached out so much that nothing fits together?
  • #3 16642191
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    I take this into account, however, before I remove the engine, I want to rule out other causes. That is why I repeat the question about supplying the shaft position sensor, the logic of the sensor is inductive and it should get 12v. Waiting for a hint.
  • #4 16642230
    paszczakq
    Level 27  
    Posts: 1011
    Help: 48
    Rate: 202
    Sooner 5V. But I do not want to mislead. Optional error reading remains maybe elsewhere is the cause.
  • ADVERTISEMENT
  • #5 16642829
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    5v is the supply for hall sensors, in this case the camshaft sensor is powered. The sensor on the crankshaft is an inductive sensor.
  • Helpful post
    #6 16676292
    -kris-
    Level 15  
    Posts: 78
    Help: 12
    Rate: 39
    Correct Supply Voltage for Shaft Position Sensor in AUDI A6 C6 3.0 tdi BMK

    it's possible that this will help you, - crankshaft is a crankshaft position and speed sensor
  • #7 16676446
    Pawel wawa
    VIP Meritorious for electroda.pl  
    Posts: 16093
    Help: 1262
    Rate: 4416
    The induction sensor does not check the power supply voltage. Probably still measured on the unfastened ankle. You can check this sensor with an oscilloscope or a LED. It will be better to measure the sensor resistance by measuring everything on the controller connector, you check the beam by the way, than the voltage on the cube. :)
  • #8 18393525
    adrian230492
    Level 1  
    Posts: 1
    Rate: 4
    Hello, will someone suggest exactly where to look for the sensor?
  • #9 18393930
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    Pawel wawa wrote:
    The induction sensor does not check the power supply voltage. Probably still measured on an unfastened ankle. You can check this sensor with an oscilloscope or a LED. It will be better to measure the sensor resistance by measuring everything on the controller connector, you check the beam by the way, than the voltage on the cube. :)
    The induction sensor is also powered, it is also required to check the correctness of the power supply. Usually it is a voltage around 5 Volts without a load which is an inductive sensor.
  • ADVERTISEMENT
  • #10 18394526
    lukashb
    Level 39  
    Posts: 5599
    Help: 416
    Rate: 414
    koszynek wrote:
    Pawel wawa wrote:
    The induction sensor does not check the power supply voltage. Probably still measured on an unfastened ankle. You can check this sensor with an oscilloscope or a LED. It will be better to measure the sensor resistance by measuring everything on the controller connector, you check the beam by the way, than the voltage on the cube. :)
    The induction sensor is also powered, it is also required to check the correctness of the power supply. Usually it is a voltage around 5 Volts without a load which is an inductive sensor.
    I have not met. So far. The induction sensor itself generated pulses, without any DC component present on its pins from the ECU side. Because what is the point to heat the coil? we are talking about a two-pin inductive sensor, a simple magnetic coil.
  • #11 18394551
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    Since I wrote that it is powered, it means it is.
  • ADVERTISEMENT
  • #12 18394646
    lukashb
    Level 39  
    Posts: 5599
    Help: 416
    Rate: 414
    I will continue to maintain that you are wrong. Insert a scan from the autodata what it says.
    I will throw a fragment from the study of dr hab. Eng. Stanisław Duera
    Quote:

    Speed and shaft position sensors
    crank (Fig. 1) are most often type sensors
    reluctance, also called magnetoinductive. Device
    these types are active and therefore producing elements
    voltage without external power supply. The permanent magnet creates a field
    magnetic, whose lines cross the turns of the coil
  • #13 18395018
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    No i'm not wrong It's as I wrote. Most of the inductive sensors I encounter in my work can generate an alternating current of about +/- 1 Volt (signal amplitude ~ 2V). These 5 Volts with a current of several dozen miles Amperes (usually 20-40) I am writing about provide a constant component for digital logic circuits. This component after connecting the sensor, which is also a resistor and load for this connection, oscillates around 2.7 Volts, and thus we get signal amplitude at the level of 0.7 Volts to 3.7 Volts. Digital logic circuits from the CMOS group can interpret such signals and any voltage above 3.4 Volts will be considered high (logic 1) while any voltage below 1 Volt will be considered low (logical 0). Thanks to this operation the driver knows what to do the sensor tells him what he saw and what he counted.

    PS When I started this thread, I did not have such knowledge, so I decided to learn and improve. What I learned many years ago, unfortunately, did not cope with current systems and realities today.
  • #14 18395130
    -kris-
    Level 15  
    Posts: 78
    Help: 12
    Rate: 39
    hi
    Correct Supply Voltage for Shaft Position Sensor in AUDI A6 C6 3.0 tdi BMK
    according to the program, both sensors are of the same type - camshaft is a camshaft
    the autodata I have has very little information about this engine
    hi
  • #15 21438811
    koszynek
    Level 12  
    Posts: 21
    Help: 1
    Rate: 23
    Further to this topic, the answer is all the parameters read were correct, the wrong flywheel was fitted to the car.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion concerns the correct supply voltage for the shaft position sensor in an Audi A6 C6 3.0 TDI with BMK engine code. The original question notes a measured voltage of 2.54 V and ongoing engine start difficulties despite sensor replacement. Responses clarify that the camshaft sensor is typically a Hall sensor powered by 5 V, while the crankshaft sensor is an inductive sensor that does not receive a DC supply voltage but generates an AC signal when the engine rotates. The inductive sensor functions as a simple magnetic coil producing pulses without a constant voltage supply. Measuring supply voltage directly on the inductive sensor is not meaningful; instead, sensor resistance and output signal should be checked with an oscilloscope or LED. The discussion also highlights that the sensor signal amplitude is around ±1 V AC, and the ECU interprets these signals digitally. A final resolution indicates that all sensor parameters were correct, and the root cause was the installation of an incorrect flywheel, which affected sensor readings and engine start performance.
Generated by the language model.

FAQ

TL;DR: Typical sensor bias is 5 V with a signal of ±1 V (≈2 Vpp). “These 5 Volts provide a constant component for digital logic circuits.” [Elektroda, koszynek, post #18395018]

Why it matters: This FAQ helps Audi A6 C6 3.0 TDI BMK owners and techs quickly diagnose hard-start issues by validating sensor power, signal, wiring, and parts fitment.

Quick Facts

What’s the correct supply for the crank/camshaft sensor on the Audi A6 C6 3.0 TDI BMK?

Users observed a typical ~5 V bias on the inductive sensor circuit without load. This bias allows clean digital interpretation of the AC signal generated by the sensor. With the sensor connected, the signal oscillates roughly between 0.7 V and 3.7 V around a ~2.7 V midpoint. That behavior aligns with CMOS logic thresholds. Use this as a functional reference, not an absolute spec sheet value. “5 V provides a constant component for digital logic circuits.” [Elektroda, koszynek, post #18395018]

Why is measuring DC power on an inductive (reluctance) sensor misleading?

A two‑pin reluctance sensor is an active element that generates voltage from a moving tone wheel and permanent magnet. It does not require external power to create the AC signal. DC checks alone can mislead diagnosis. Use resistance checks at the ECU and view waveform while cranking. “The induction sensor does not check the power supply voltage.” [Elektroda, Pawel wawa, post #16676446]

How should I test the crankshaft sensor correctly?

Use this three-step method: 1. Measure sensor resistance at the ECU connector to verify the harness. 2. Crank the engine and view the waveform with an oscilloscope or a test LED. 3. Compare cylinder sync and pattern consistency across several seconds of cranking. This avoids false conclusions from open-plug DC readings. [Elektroda, Pawel wawa, post #16676446]

I read 2.54 V on the plug—what does that mean?

A mid-level reading near 2.5–2.7 V suggests a biased input awaiting the AC signal. When the inductive sensor swings, the ECU sees roughly 0.7–3.7 V. That range crosses logic thresholds for reliable edge detection. Treat 2.54 V as a bias indicator, then validate the waveform while cranking. [Elektroda, koszynek, post #18395018]

Are both camshaft and crankshaft sensors the same type on this engine?

Referenced program data shown in the thread lists both sensors as the same type for the BMK engine. This aligns troubleshooting steps and expected test methods for each sensor. Always confirm by part number before replacing components. [Elektroda, -kris-, post #18395130]

Is a 12 V supply expected on the inductive sensor?

No. The thread’s final technical position shows a ~5 V bias used for signal conditioning and digital interpretation. The inductive element produces the AC component; the ECU bias sets a usable reference. Do not chase a missing 12 V on a two‑pin reluctance sensor. [Elektroda, koszynek, post #18395018]

Could stretched timing chains cause my hard starting instead of the sensor?

Yes. Early in the discussion, timing chain stretch was raised as a plausible cause when signals and power seem off. If patterns look irregular or phase correlation fails, inspect timing before replacing sensors. Chain and guide wear can desync cam/crank relationships. [Elektroda, paszczakq, post #16642145]

Where is the crankshaft sensor located on the BMK in this thread?

The thread does not provide a confirmed physical location. The requester asked where to find it, but no exact placement followed. Consult the factory manual or official parts catalog for location and access steps on your VIN. [Elektroda, adrian230492, post #18393525]

What waveform or amplitude should I see while cranking?

Expect about ±1 V around a DC bias when referenced to ECU ground, yielding roughly 2 V peak‑to‑peak. With the designed bias, the observable swing is around 0.7–3.7 V. Stable, periodic teeth and known gaps should be visible and repeat each revolution. [Elektroda, koszynek, post #18395018]

What current does the bias path use, and why does it matter?

The reported bias path uses approximately 20–40 mA. That current sets the mid-level and helps the ECU register clean transitions from the sensor’s AC output. A short or open will shift this current and disturb the bias, producing starting issues. [Elektroda, koszynek, post #18395018]

How do I check the harness without back-probing at the sensor?

Measure the sensor circuit resistance directly at the ECU connector. This validates both the sensor coil and the entire run of wiring in one step. It also reveals high resistance, opens, or shorts without disturbing the sensor plug. Then scope the signal while cranking. [Elektroda, Pawel wawa, post #16676446]

My readings look fine. What obscure fault should I consider?

Consider a mismatched or incorrect flywheel. The original poster later confirmed that all parameters appeared correct, yet a wrong flywheel caused the no‑start/hard‑start condition. Tooth count or indexing errors can defeat sync despite healthy sensors. [Elektroda, koszynek, post #21438811]

What is an inductive (reluctance) sensor in simple terms?

It is a two‑pin magnetic pickup with a coil and permanent magnet. A passing toothed wheel changes the magnetic field, inducing an AC voltage. It creates its own signal without needing external power to generate the alternating component. [Elektroda, lukashb, post #18394646]

Why can measuring on an unplugged connector mislead diagnosis?

An unplugged connector lets you see only the ECU’s bias or floating voltage, not the true loaded condition. Plugged-in measurements or back‑probing with the sensor connected reflect actual behavior. Always validate under load while cranking. [Elektroda, Pawel wawa, post #16676446]

What ultimately solved the original hard-start complaint here?

The car had an incorrect flywheel installed. Once identified, this explained the persistent starting problems despite sensors and readings appearing normal. Correcting the flywheel resolved the issue. [Elektroda, koszynek, post #21438811]
Generated by the language model.
ADVERTISEMENT