P0849 code meaning
Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent
Powertrain system Generic code P08xx codes Check engine light
What P0849 means
Transmission fluid pressure sensor/switch A and B are inputs inside the automatic gearbox. A switch only reports pressure present or absent, a sensor reports a value. The letter is the maker's choice: Allison 1000 uses A and B for the switches on shift valves S1 and S2, GM's CVT for the primary and secondary pulley sensors, GM's 2025 8-speed A for the lube pressure sensor; Ford reports pressure faults under its solenoid codes instead. P0849 reports short dropouts of the B signal. GM bulletin 21-NA-033 for the Corvette C8 dual clutch lists it with P0841, P0844 and P0846: first the valves are cleaned and the clutches relearned, and only if the code comes back on its own is the circuit traced. Like the A counterpart P0844 it has no published thresholds.
P0849 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0849
- Warning lamp coming and going
- Occasional shift shocks
- Brief limp mode
Common causes of P0849
- Most likelyLoose contact or corrosion at the gearbox connector or control unit
- PossibleDirt in valve or sensor causing signal jumps
- PossibleSensor faulty internally
- Less likelyChafed spot in the harness
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Transmission fluid pressure sensorTransmission valve bodyTransmission wiringTransmission control module
What each part of P0849 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 8 | Area: transmission. |
| 49 | The exact fault in that area. |
What to do next
- Note P0849 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0849
What does P0849 mean?
P0849 means "Transmission Fluid Pressure Sensor/Switch B Circuit Intermittent". Transmission fluid pressure sensor/switch A and B are inputs inside the automatic gearbox. It is a generic code, so it means the same on every make.
Is it safe to drive with P0849?
Drive gently and only to a workshop. With P0849 the car can go into limp mode (reduced power) to protect itself.
Will P0849 fail an emissions test?
Yes, it can. P0849 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0849 to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P0849 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.