The P077B: Output Speed Sensor Circuit – Direction Error refers to an issue where the transmission control module (TCM) detects an incorrect direction signal from the output speed sensor. This may cause issues with gear shifting and overall transmission performance. The problem can stem from a faulty sensor, wiring problems, or connector issues.
P077B – Quick Overview
| Code | Information |
|---|---|
| Meaning | P077B: Output Speed Sensor Circuit – Direction Error |
| Is it serious? | Yes, incorrect direction signals can cause erratic shifting and potential transmission damage. |
| Possible causes | – Incorrect direction signal from output speed sensor – Faulty output speed sensor – Wiring or connector issues |
| How to diagnose? | – Test output speed sensor for direction accuracy – Inspect wiring and connectors – Replace faulty sensor if needed |
P077B Meaning
The P077B code indicates that the output speed sensor is sending an incorrect direction signal to the transmission control module (TCM). This sensor monitors the rotation and direction of the transmission’s output shaft, and an incorrect signal can cause poor shifting, gear slippage, or even transmission failure.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for other transmission-related codes that could provide additional information on the issue. | OBD-II Scanner |
| Test Output Speed Sensor for Direction Accuracy | Use a multimeter or diagnostic scanner to test the output speed sensor for correct directional signals. Compare the readings against manufacturer specifications. | Multimeter, Diagnostic Scanner |
| Inspect Wiring and Connectors | Visually inspect the wiring and connectors leading to the output speed sensor for signs of damage, wear, or corrosion that may cause inaccurate signals. | Flashlight, Multimeter, Safety Gloves |
| Check Transmission Fluid | Ensure that the transmission fluid level is correct and that the fluid is clean, as contaminated or low fluid can affect sensor performance. | Transmission Fluid Tester, Dipstick |
| Replace Faulty Sensor | If the output speed sensor is found to be faulty or providing incorrect signals, replace it with a new one according to manufacturer specifications. | Replacement Parts, Wrenches, Screwdrivers |
| Clear the Code and Test Drive | After replacing the sensor, clear the code using an OBD-II scanner and take the vehicle for a test drive to verify that the issue is resolved. | OBD-II Scanner |
| Recheck for Codes | After the test drive, rescan the vehicle to ensure the P077B code has not returned. | OBD-II Scanner |
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