The P0878: Transmission Fluid Pressure Sensor/Switch ‘D’ Circuit High fault code indicates that the transmission fluid pressure sensor or switch ‘D’ is detecting higher-than-expected voltage. This issue can cause improper transmission fluid pressure monitoring, leading to shifting problems and potential damage to transmission components. Possible causes include a faulty sensor, wiring issues, or a malfunctioning transmission control module (TCM).
P0878 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P0878: Transmission Fluid Pressure Sensor/Switch ‘D’ Circuit High |
| Is it serious? | Yes, it can cause improper transmission operation and shifting issues. |
| Possible causes | – High voltage in the transmission fluid pressure sensor/switch ‘D’ circuit – Faulty sensor or wiring – Faulty transmission control module (TCM) |
| How to diagnose? | – Test the circuit for high voltage – Inspect wiring and connectors – Replace faulty components if needed |
P0878 Meaning
The P0878: Transmission Fluid Pressure Sensor/Switch ‘D’ Circuit High code indicates that the voltage in the transmission fluid pressure sensor/switch ‘D’ circuit is higher than the specified range. This high voltage can cause incorrect fluid pressure readings, leading to improper shifting and potential transmission issues.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for any additional related codes that may provide further insights into the transmission issue. | OBD-II Scanner |
| Test the Circuit for High Voltage | Use a multimeter to measure the voltage in the transmission fluid pressure sensor/switch ‘D’ circuit and compare it to manufacturer specifications. | Multimeter |
| Inspect Wiring and Connectors | Visually inspect the wiring and connectors for damage, corrosion, or loose connections that could be causing the high voltage reading. | Flashlight, Multimeter |
| Test Transmission Control Module (TCM) | Use a diagnostic tool to ensure the TCM is functioning properly and communicating with the sensor/switch ‘D’ correctly. | Diagnostic Tool |
| Replace Faulty Components | If the sensor, wiring, or TCM is found faulty, replace the necessary components to restore normal transmission fluid pressure monitoring. | Replacement Parts, Basic Tools |
| Clear the Code and Test Drive | After repairs, clear the code using an OBD-II scanner and test drive the vehicle to ensure proper transmission function. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | After the test drive, re-scan the system to confirm that the P0878 code does not return. | OBD-II Scanner |
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Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)