TCM Engine Speed Output Circuit High
What it means
P0739 means the transmission control module detected an abnormally high voltage in its engine-speed output circuit — the line it uses to pass an RPM signal on to other systems. It typically points to a wiring short to voltage, a bad connector, or a faulty speed sensor rather than an engine problem, so the car still starts and runs but may shift harshly and share an incorrect RPM reading with other modules.
Can I keep driving? Usually drivable — the engine starts and runs, but shifting may be harsh or erratic and other modules sharing the RPM signal may read it wrong; get it diagnosed.
Common symptoms
What you'll notice
- Check-engine light on
- Harsh, delayed, or erratic shifting
- Incorrect engine-speed readings passed to other modules
- Possible gauge or shift-timing irregularities
Common causes
Most likely first
- Short to voltage in the engine-speed output circuit wiringLikely
- Corroded or damaged connector in the output circuitCommon
- Faulty engine-speed sensor feeding the signalCommon
- Faulty transmission control module (less common)Less often
How to diagnose & fix
Work through it in order
- Scan and check the engine-speed value the module is outputting against actual RPM.
- Inspect the output-circuit wiring for a short to a voltage source or chafed insulation.
- Check the connectors in the circuit for corrosion or spread terminals.
- Test the engine-speed sensor; suspect the control module only after wiring is verified. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0739?+
Can I just clear P0739?+
Related codes
Often seen with P0739
Read & clear P0739 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.