Transmission Fluid Pressure Sensor/Switch D Circuit High
The P0878 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch D Circuit High. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $100 - $500 (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 P0878?
- Check Engine Light illuminated
- Harsh shifting in certain gear ranges
- Firm engagement when selecting gear
- TCM may restrict available gears
What Causes P0878? (Most Likely First)
- Open ground at pressure sensor D Very High
- Faulty pressure sensor D stuck reading high High
- Short to voltage in sensor D signal wire Moderate
- TCM reference voltage fault for sensor D Low
Can I Still Drive with P0878?
Short distances only. P0878 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
Is P0878 the high counterpart of P0877?
Yes, P0877 indicates sensor D signal is too low, and P0878 indicates it is too high. They represent opposite electrical conditions in the same circuit.
Can an open ground wire be hard to find?
Open grounds can be tricky because the wire may look intact externally but be broken internally. A continuity test with a multimeter is needed to confirm.
Will the transmission work normally if sensor D reads high?
The TCM may make incorrect shift decisions based on the false high reading. Shift quality will be degraded and the TCM may limit gear selection as a protective measure.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0878?
-
Measure voltage at sensor D connector with key on
-
Check for an open ground at the sensor
-
Test for short to battery voltage on the signal wire
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Replace sensor D if circuit checks pass
Sources 2
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)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Which Vehicles Commonly Get P0878?
- 2017-2020 Ford F-250 (10R80)
- 2015-2019 Chevrolet Suburban (8L90)
- 2014-2020 Dodge Durango (ZF 8HP)
- 2016-2020 Honda Ridgeline
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