Transmission Fluid Pressure Sensor/Switch C Circuit
What does P0870 mean?
The P0870 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch C Circuit. This is a moderate severity code.
Common Symptoms
- Check Engine Light illuminated
- Erratic shifting in specific gears
- Transmission slip during certain shift events
- Possible limp mode
Probable Causes (Ranked by Likelihood)
- Faulty transmission fluid pressure sensor C Very High
- Wiring fault in pressure sensor C circuit High
- Corroded connector at sensor C Moderate
- Internal valve body issue affecting sensor C circuit Low
Step-by-Step Diagnostic Procedure
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Check transmission fluid level and condition
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Monitor pressure sensor C data on a scan tool and compare to sensors A and B
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Inspect wiring and connector at pressure sensor C
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Test sensor C resistance and compare to manufacturer specifications
Frequently Asked Questions
Why does my transmission have three pressure sensors?
Modern transmissions with 8 or more speeds use multiple pressure sensors to monitor different hydraulic circuits. Sensor C typically monitors a third pressure circuit for additional shift control precision.
Is sensor C diagnosed the same way as A and B?
Yes, the diagnostic approach is the same: check fluid level, monitor sensor data, inspect wiring, and compare readings to specifications.
Are all pressure sensors the same part?
Not always. While some vehicles use identical sensors in all positions, others use different sensors calibrated for different pressure ranges. Always verify the correct part number.