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P2747 – Intermediate Shaft Speed Sensor 'B' Circuit No Signal (OBD2)

P2747 means "Intermediate Shaft Speed Sensor 'B' Circuit No Signal". The control unit receives no signal at all from the transmission speed sensor, so it cannot use this information and switches to substitute values.

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P2747 quick summary

Fault codeP2747
MeaningIntermediate Shaft Speed Sensor 'B' Circuit No Signal
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?Carefully and only to a workshop. The gearbox will often stay in one gear (limp mode).
Repair cost€30 – €500

How gearbox speed sensors work

Gearbox speed sensors measure input (turbine), intermediate and output shaft speed; the control unit uses them to choose gears, control shift quality and detect slipping.

The input or turbine speed sensor measures the speed coming from the torque converter; the output speed sensor measures the speed going to the wheels; some gearboxes also measure an intermediate shaft. Comparing them tells the control unit which gear is engaged and whether clutches are slipping.

Codes P0715–P0718 (input/turbine), P0720–P0723 (output) and P0791–P0794 (intermediate shaft) report circuit, range, no signal and intermittent faults.

A missing speed signal usually puts the gearbox into limp mode and can disable the speedometer and cruise control. Causes include failed sensors, metal debris on magnetic sensors, wiring and connector faults.

Symptoms of P2747

  • Gearbox stuck in one gear or harsh shifts
  • Speedometer not working (output sensor)
  • Cruise control not working
  • Flare or slipping between gears
  • Check Engine or gearbox warning

Most common causes of P2747 (most likely first)

Mechanic's Pro Tip

If a magnetic speed sensor is covered in metal paste, clean it but also find out where the debris comes from – it may be a symptom of internal gearbox wear.

  1. 1.Open circuit in the signal, supply or ground wire

    Most likely

  2. 2.Faulty transmission speed sensor

  3. 3.Damaged trigger wheel or wrong air gap (speed and position sensors)

    Metal debris on a magnetic sensor tip can also block the signal.

  4. 4.Metal debris on the sensor tip

  5. 5.Wiring or connector fault

  6. 6.Internal harness or control unit fault

Step-by-step diagnostic guide

  1. 1

    Read codes and speed values

    Read the transmission codes and compare input, intermediate and output speeds in live data while driving slowly.

  2. 2

    Check the signal at the sensor

    Check supply and ground at the transmission speed sensor connector, then look at the signal while cranking or driving – ideally with an oscilloscope, otherwise with a multimeter on AC volts (inductive sensors) or DC volts (Hall sensors).

    Multimeter: Hall sensors: square wave switching between about 0 V and 5 V (or 12 V). Inductive sensors: AC voltage rising with speed, often from about 0.5 V AC upwards when cranking.

  3. 3

    Inspect the sensor

    Remove the sensor (if external) and check for debris and damage.

  4. 4

    Measure the sensor

    Check the supply and signal on Hall sensors, resistance and AC output on inductive sensors.

    Multimeter: Inductive sensors: typically a few hundred ohms to about 1.5 kΩ.

  5. 5

    Check fluid for debris

    Heavy metal debris in the fluid points to internal wear causing the sensor fault.

  6. 6

    Replace and verify

    Replace the sensor or harness, clear codes and confirm normal shifting.

How do I read fault codes? →Where the OBD2 port is, which scanner to use and how to read and clear codes step by step.

Frequently asked questions

Can I keep driving with P2747?

Carefully and only to a workshop. The gearbox will often stay in one gear (limp mode).

How much does it cost to fix P2747?

Typical repair costs are 30 € – 500 €, depending on the cause and the vehicle. The most common fixes are: open circuit in the signal, supply or ground wire; faulty transmission speed sensor; damaged trigger wheel or wrong air gap (speed and position sensors). Always confirm the cause with the tests above before buying parts.

Can a speed sensor cause limp mode?

Yes. Without reliable speed signals, the gearbox cannot shift properly and protects itself.

Is the speedometer connected to the gearbox speed sensor?

On some cars yes (output speed sensor); on most modern cars the speedometer uses ABS wheel speed data.

What is the difference between P2747 and similar codes?

P2747 belongs to a group of codes for the same component that differ in the type or location of the fault: P0794 – Intermediate Shaft Speed Sensor Circuit Intermittent; P2745 – Intermediate Shaft Speed Sensor 'B' Circuit; P2746 – Intermediate Shaft Speed Sensor 'B' Circuit Range/Performance; P2748 – Intermediate Shaft Speed Sensor 'B' Circuit Intermittent; P2765 – Input/Turbine Speed Sensor 'B' Circuit; P2766 – Input/Turbine Speed Sensor 'B' Circuit Range/Performance. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.