P0879 code meaning
Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent
Powertrain system Generic code P08xx codes Check engine light
What P0879 means
Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. They are more widespread than A and B: GM's 6L80/6L90 and 6T40/6T70 six-speeds put switch C on the 2-6 brake and D on the 1-2-3-4 clutch, Allison uses them for its third shift valve and its reverse switch, Ram's RFE gearboxes for the clutch pressure switches in the solenoid block. Ford reports pressure faults under its solenoid codes. P0879 reports short dropouts of the D signal. Like P0874 it is documented only for the Corvette C8 dual clutch in GM bulletin 21-NA-033, with MIL: clean the valves, relearn, then trace the circuit if the code returns. No thresholds are published.
P0879 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0879
- Warning lamp coming and going
- Occasional harsh shift or limp mode
Common causes of P0879
- Most likelyLoose contact or corrosion at connector or harness
- PossibleDirt or sticking valve (dual clutch)
- PossibleSensor or switch with dropouts
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 P0879 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. |
| 79 | The exact fault in that area. |
What to do next
- Note P0879 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 P0879
What does P0879 mean?
P0879 means "Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent". Transmission fluid pressure switches C and D report whether a clutch circuit is pressurised. It is a generic code, so it means the same on every make.
Is it safe to drive with P0879?
Drive gently and only to a workshop. With P0879 the car can go into limp mode (reduced power) to protect itself.
Will P0879 fail an emissions test?
Yes, it can. P0879 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 P0879 to fix?
Difficulty: medium. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P0879 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.