P0870 means Transmission Fluid Pressure Sensor/Switch C Circuit. The transmission computer has detected a general fault in the pressure sensor or switch C circuit, which reports whether hydraulic pressure is present in a clutch circuit. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0870 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0870 symptoms
- Check engine light
- Limp mode or a gear held
- Harsh or missing shifts
Common causes of P0870
- Low fluid level
- Damaged internal harness or connector
- Failed pressure switch or switch manifold
- Sticking valve or internal leak in the related circuit
How to diagnose P0870
- Check transmission fluid level and condition first
- Inspect the case connector and internal harness
- Read live pressure switch states on a scan tool while shifting
- Check for other pressure switch or solenoid codes that share a circuit
Can you drive with P0870?
Only as needed; get it checked before the transmission is damaged by wrong pressure.
P0870 tips
On many transmissions the pressure switches are part of a switch manifold in the valve body, so replacement means dropping the pan.
Will P0870 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0870 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0871 | Transmission Fluid Pressure Sensor/Switch C Circuit Range/Performance |
| P0872 | Transmission Fluid Pressure Sensor/Switch C Circuit Low |
| P0873 | Transmission Fluid Pressure Sensor/Switch C Circuit High |
Guides that help
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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