Damaged wiring, poor connector contact or corrosion in the engine speed signal circuit between the sensor or ECU and the TCM; Faulty crankshaft position sensor or its supply or earth, so no RPM signal is generated; Faulty engine speed sensor or input speed sensor on the transmission, where fitted; Communication fault on the data network (CAN) carrying the engine speed message; Low system voltage, poor battery or earth connections causing signal dropouts; Faulty transmission control module or engine control unit; Outdated control unit software where a manufacturer bulletin identifies it as a cause.

P0727

Engine Speed Input Circuit No Signal.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
27: FaultThe specific fault in that area

What it means

P0727 means the transmission control module has detected no signal from the engine speed input circuit. The TCM expects an engine speed (RPM) signal, usually shared from the engine control unit or a crankshaft sensor, and sees nothing while other data suggests the engine is running. The way the signal is supplied varies by model and transmission.

Symptoms

Malfunction indicator lamp or transmission warning lamp on
Transmission going into limp mode or fixed gear
Harsh, delayed or erratic gear changes
Rev counter dropping to zero or behaving erratically
Torque converter lock-up not engaging, with poor economy
Engine stalling or hard starting if the engine speed signal fault is shared

Possible causes

Damaged wiring, poor connector contact or corrosion in the engine speed signal circuit between the sensor or ECU and the TCMlikely
Faulty crankshaft position sensor or its supply or earth, so no RPM signal is generatedlikely
Faulty engine speed sensor or input speed sensor on the transmission, where fittedpossible
Communication fault on the data network (CAN) carrying the engine speed messagepossible
Low system voltage, poor battery or earth connections causing signal dropoutspossible
Faulty transmission control module or engine control unitrare
Outdated control unit software where a manufacturer bulletin identifies it as a causerare

How to diagnose

Read all stored and pending codes from engine and transmission modules, and note any crank sensor, CAN or low voltage codes
Review freeze frame data to see engine speed, vehicle speed, gear and temperature when the code set
Check live data: compare engine RPM shown by the engine control unit and the TCM while cranking and running
Inspect the wiring, connectors and earths for the crank sensor, engine speed circuit and TCM for damage, water, oil or corrosion
Test battery condition and charging voltage, and check the main earth and supply connections
Check the crankshaft sensor signal and its supply and earth with a multimeter or oscilloscope against the manufacturer's specification
Check network communication for faults and test continuity and resistance of the signal wiring
Check for software updates or technical bulletins for the model and transmission, then consider module testing only after wiring and sensors are cleared

How to fix

Repair or replace damaged wiring and clean or replace faulty connectors
Replace a faulty crankshaft position sensor or transmission speed sensor
Repair network communication faults found during testing
Restore good battery, charging and earth connections
Update control unit software only if a known fault is documented for the vehicle
Replace or recode a confirmed faulty control module as per manufacturer procedure

Can I keep driving?

Medium severity

The car may be drivable in limp mode, but gear changes may be harsh and the fault could worsen or cause stalling if the engine signal is lost. Have it checked soon and avoid long journeys or heavy loads until repaired.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.