P0873 code meaning
Transmission Fluid Pressure Sensor/Switch C Circuit High
What P0873 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. P0873 means switch C reports no pressure although its clutch should be applied. GM checks it when the 2-6 brake is commanded above 700 kPa and sets it after 15 counts on the 6L80 or 20 on the 2010 6T70, without MIL. Allison sets it after 0.125 s (2006) or 0.175 s (2007) without pressure at an applied valve, then tells electrical from mechanical by the companion solenoid code, type A.
P0873 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0873
- Code stored in the gearbox module; on GM without MIL, on Allison with MIL
- Shift shock or slip in gears using clutch C
Common causes of P0873
- Most likelySignal wire or connector open (gearbox pass-through, harness)
- PossiblePressure switch does not close (diaphragm, seal)
- PossibleClutch pressure does not build: low fluid, leak, regulator valve
- Less likelyGearbox module input
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 P0873 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. |
| 73 | The exact fault in that area. |
What to do next
- Note P0873 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 P0873
What does P0873 mean?
P0873 means "Transmission Fluid Pressure Sensor/Switch C Circuit High". 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 P0873?
Drive gently and only to a workshop. With P0873 the car can go into limp mode (reduced power) to protect itself.
Will P0873 fail an emissions test?
P0873 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0873 to fix?
Difficulty: hard. A typical repair takes 1 to 5 hours of work. This is a job for a workshop.
Will P0873 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.