Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent
The P0879 code means the vehicle's onboard diagnostic system has detected: Transmission Fluid Pressure Sensor/Switch D Circuit Intermittent. 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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Common Symptoms
- Check Engine Light illuminated intermittently
- Occasional shift quality issues
- Sporadic transmission warning light
- Shifting inconsistency that comes and goes
Probable Causes (Ranked by Likelihood)
- Loose connector at pressure sensor D Very High
- Intermittent break in sensor D wiring High
- Sensor D internal failure with sporadic output Moderate
- Vibration-induced wiring fault near transmission Moderate
Frequently Asked Questions
How do I catch an intermittent sensor D fault?
Use a scan tool with data logging capability to record sensor D readings over multiple drive cycles. Review the data for sudden dropouts or spikes.
Can tightening the connector fix the code?
If the connector is loose, firmly reseating it and applying dielectric grease may resolve the intermittent connection. Clear the code and monitor.
Should I replace the sensor if the code keeps returning?
If the wiring and connector are confirmed good after thorough inspection, replacing the sensor is the next logical step.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Wiggle test on sensor D connector while monitoring live data
-
Inspect wiring harness for chafing near transmission mounting points
-
Data-log sensor D readings over several drive cycles
-
Check connector pins for signs of corrosion or looseness
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
Commonly Affected Vehicles
- 2017-2020 Ford Expedition (10R80)
- 2015-2019 GM Sierra (8L90)
- 2014-2020 Jeep Cherokee (ZF 9HP)
- 2016-2020 Toyota Tacoma
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