Transmission Fluid Pressure Sensor/Switch C Circuit
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.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $150 - $600 (parts and labor)
Read and clear transmission codes. Many trans codes are caused by low or burnt fluid -- check level and color before assuming the worst.
Basic scanners only read engine codes. This reads transmission, ABS, and airbag too.
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What Are the Symptoms of P0870?
- Check Engine Light illuminated
- Erratic shifting in specific gears
- Transmission slip during certain shift events
- Possible limp mode
What Causes P0870? (Most Likely First)
- 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
Can I Still Drive with P0870?
Short distances only. P0870 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
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.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0870?
-
Check transmission fluid level and condition
-
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
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Which Vehicles Commonly Get P0870?
- 2010-2020 Ford F-150 (10R80)
- 2012-2019 Chevrolet Silverado (8L90)
- 2008-2018 Honda Accord (9-speed)
- 2011-2019 Jeep Grand Cherokee (ZF 8HP)
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