P0727: Engine Speed Input Circuit No Signal
What to do
Expect a fixed gear. If the rev counter is also dead, that is part of the same fault. The engine running normally is itself informative — it means the crankshaft sensor is working and the problem is in how its signal reaches the gearbox.
What this code means
No engine speed value at all reaching the transmission module while the engine is running. The transmission cannot schedule anything sensibly without it and will default to a fixed gear.
If the crankshaft position sensor were genuinely dead the engine would not be running, so a no-signal fault reported by the transmission while the engine runs normally points at the path rather than the source — a bus fault, a wiring break on a hard-wired tachometer feed, or the transmission module's own input stage. A dead rev counter alongside this code is a useful confirmation that the signal is missing generally rather than only at the transmission.
Likely causes
Start here
- Loss of communication with the engine control module · specialist
- Open circuit in engine speed wiring · moderate
Less common
- Damaged data bus wiring · specialist
- Faulty crankshaft position sensor · moderate
- Faulty transmission control module · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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