Faulty or dirty crankshaft position sensor, or damaged sensor reluctor ring; Damaged wiring, poor connections or corrosion in the engine speed signal circuit between the engine ECU, TCM and sensor; Electrical interference or a poor earth or power supply to the TCM or engine ECU; Faulty transmission input speed sensor causing a mismatch with engine speed; Torque converter slip or internal transmission fault causing a speed disagreement; Faulty TCM or engine ECU, or outdated software where this is a known issue for the model.

P0726

Engine Speed Input Circuit Range/Performance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

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

What it means

P0726 is the generic code for an engine speed input circuit range or performance problem. The transmission control module compares the engine speed signal it receives, normally from the engine control unit or crankshaft sensor, with the transmission input speed and other data. If the signal is implausible, erratic or does not agree with what the TCM expects, the code is set.

Symptoms

Gearbox warning light or engine management light on
Transmission in limp mode or stuck in one gear
Harsh, delayed or flared gear changes
Erratic or unresponsive rev counter
Torque converter lock-up not working, or poor fuel economy
Engine misfire or stalling if the crankshaft signal is also faulty

Possible causes

Faulty or dirty crankshaft position sensor, or damaged sensor reluctor ringlikely
Damaged wiring, poor connections or corrosion in the engine speed signal circuit between the engine ECU, TCM and sensorlikely
Electrical interference or a poor earth or power supply to the TCM or engine ECUpossible
Faulty transmission input speed sensor causing a mismatch with engine speedpossible
Torque converter slip or internal transmission fault causing a speed disagreementpossible
Faulty TCM or engine ECU, or outdated software where this is a known issue for the modelrare

How to diagnose

Read all stored and pending codes from both the engine and transmission modules, and note the freeze frame data.
Look for related engine codes such as crankshaft sensor faults, misfires or CAN communication faults, and deal with those first.
Check transmission fluid level and condition, as the correct procedure and fluid type depend on the model.
Inspect the wiring, connectors and earths for the crankshaft sensor, input speed sensor, TCM and engine ECU for damage, chafing, water or corrosion.
Compare live engine speed from the engine ECU with the rev counter and the engine speed value shown by the TCM, on a test drive or at idle.
Check battery condition and charging voltage, as low voltage can upset signals.
Test the crankshaft sensor signal and supply with a multimeter or oscilloscope, following the manufacturer's specification for the engine, and inspect the reluctor ring.
Check for applicable software updates or technical bulletins for the vehicle, and test the input speed sensor and TCM only after the other checks.

How to fix

Replace a faulty crankshaft position sensor or repair or replace a damaged reluctor ring.
Repair or replace damaged wiring, connectors or earths in the engine speed signal circuit.
Correct battery or charging faults that cause unstable voltage.
Replace a faulty transmission input speed sensor.
Repair the transmission or torque converter if internal slip is confirmed.
Update the control unit software if an outdated version is a known cause, or repair or replace a confirmed faulty TCM or engine ECU.

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but limp mode and harsh shifts can stress the gearbox, so book it in soon. Avoid heavy loads and long journeys, and stop if the engine stalls or the gearbox slips badly.

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