What Does P0879 Mean?
The TCM has detected an intermittent fault in the transmission fluid pressure sensor/switch 'D' circuit. The signal is periodically dropping out, spiking, or behaving erratically in a way that does not match expected hydraulic pressure patterns. This intermittent behavior typically worsens over time as connector corrosion or wire damage progresses.
Common Causes
35%
Loose or corroded connector at pressure sensor 'D'
25%
Chafed or broken wire in sensor 'D' harness
20%
Failing pressure sensor 'D' with thermal-dependent intermittent
12%
Intermittent contact at TCM connector
8%
Transmission fluid intrusion into connector causing intermittent shorts
Diagnostic Steps
1
Monitor live data for sensor 'D' while road testing — note when signal dropouts occur relative to temperature, RPM, and vibration.
2
Perform a wiggle test on the sensor connector and harness while observing the live PID for signal interruptions.
3
Inspect the sensor connector for bent pins, spread terminals, broken lock tabs, or fluid contamination.
4
Check the wiring harness routing for abrasion points, especially near the transmission case and exhaust heat shields.
5
If connections are solid, replace the sensor as internal intermittents cannot be reliably repaired.
Estimated Repair Cost
$80 - $450
Parts + labor, varies by vehicle and location
The TCM has detected an intermittent fault in the transmission fluid pressure sensor/switch 'D' circuit. The signal is periodically dropping out, spiking, or behaving erratically in a way that does not match expected hydraulic pressure patterns. This intermittent behavior typically worsens over time...
The most common cause of P0879 (Transmission Fluid Pressure Sensor/Switch "D" Circuit Intermittent) is: Loose or corroded connector at pressure sensor 'D'
Typical repair costs for P0879 range from $80 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Generally safe for short-distance driving. Occasional shift hesitation or firmness may occur. Schedule diagnosis soon as intermittent faults tend to worsen progressively.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0879 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Hydraulic Pressure Monitoring
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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