Input/Turbine Speed Sensor "A" Circuit Range/Performance

Possible causes

• CommonSlipping clutch or band inside the transmission, so the speeds really are wrong
• CommonFailing or inaccurate speed sensor
• CommonMetal debris or damage on the reluctor ring the sensor reads
• CommonLow or degraded fluid causing a genuine slip
• PossibleWrong sensor or wrong tyre size affecting the calculation
• PossibleWiring interference or a poor earth corrupting the signal

What you might notice

• Slipping - engine speed rises without the car accelerating
• Harsh, flaring or delayed shifts
• Transmission dropping into limp mode
• Speedometer reading wrong
• Check engine light on

What to check, in order

1. Establish first whether the transmission is actually slipping. If engine speed rises without the car speeding up, the sensors are telling the truth and the fault is mechanical.
2. Check the fluid level and condition before anything else. Low or burnt fluid causes real slip, and real slip sets this code with perfectly good sensors.
3. Watch input and output speed together on the live data screen. Work out the ratio in each gear and compare it with the specification.
4. Check for gear ratio codes stored alongside. Those confirm a mechanical problem rather than a sensor one.
5. Ask whether non-standard tyre or wheel sizes have been fitted, which shifts every speed-derived calculation.
6. Replace the sensor only after mechanical slip has been ruled out. A new sensor will not fix a worn clutch pack.