U0679Lost Communication With Transmission Fluid Pressure Sensor/Switch A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Automatic transmissions measure hydraulic pressure to confirm that a clutch or pulley really received the pressure the controller asked for. Which sensor is A varies: Ford's 2024 summary calls the sensors of its 10R60/10R80 and 8F units TFP A and B, analog with 0.5 to 4.5 V for 0 to 2,500 kPa, and sets P0841 when the reading sticks although the clutch still applies and releases. GM's 24OBDG07 assigns A to clutch 1 (P0842 below 220 mV, P0843 above 4,530 mV after 150 ms), while its CVT table 25OBDG03A uses A for the primary pulley. U0679 covers a digital sensor A that has gone silent. No manufacturer documents this code publicly. The transmission controller then loses its pressure feedback and may hold a gear or shift harshly.
- What you may notice
- Harsh or delayed shifts
- Transmission stays in a fixed gear
- Check engine or transmission warning light
- Likely causes
- LikelyTransmission internal harness or lead frame to sensor A damaged
- PossibleTransmission case connector leaking oil or corroded
- PossiblePressure sensor A electronics failed
- RareTransmission control module input or software fault
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.