The Toyota Code P0139 is a common fault code that appears when a malfunction is detected in the oxygen sensor circuit slow response (Bank 1 Sensor 2). This code is triggered when the HO2 sensor voltage does not drop below 0.2 V immediately after fuel cut starts, or when the voltage does not drop from 0.35V to 0.2 V immediately after fuel cut starts. There are several common causes of this issue, including a short in the HO2 sensor circuit, a faulty HO2 sensor, or a malfunction of the ECM. Proper diagnosis and repair is needed to resolve the problem, as outlined in the related service bulletin G0G. To better understand the causes and solutions to this issue, a table is provided below.
Causes and Solutions for Toyota Code P0139
| Cause | Solution |
|---|---|
| Short in HO2 sensor (for Bank 1 Sensor 2) circuit | Check wiring and connectors for signs of damage and repair as necessary |
| HO2 sensor (for Bank 1 Sensor 2) | Replace the faulty sensor |
| ECM | Check programming and replace the ECM if needed |
| Fuel Cut | Check the fuel cut system and verify it is functioning correctly |
Toyota Code P0139 is a fault code that indicates an issue with the oxygen sensor circuit slow response (Bank 1 Sensor 2). This code is triggered when the HO2 sensor voltage fails to drop below 0.2 V immediately after fuel cut starts, or does not drop from 0.35 V to 0.2 V immediately after fuel cut starts. Common causes of this code include a short in the HO2 sensor circuit, a faulty HO2 sensor, or a malfunction of the ECM. To help diagnose and repair the issue, it is important to understand the causes and solutions associated with the Toyota Code P0139.
Short in HO2 Sensor Circuit
The first cause of the Toyota Code P0139 is a short in the HO2 sensor circuit (for Bank 1 Sensor 2). This is caused by an electrical short in the wiring or connectors that is preventing the sensor from functioning correctly. To repair this problem, it is necessary to check the wiring and connectors for any signs of damage. If any damage is found, it must be repaired as soon as possible.
HO2 Sensor
The second cause of the Toyota Code P0139 is a faulty HO2 sensor (for Bank 1 Sensor 2). This is caused by the sensor itself failing to function properly, which can be caused by a variety of factors. To repair this issue, the faulty sensor must be replaced with a new one.
ECM
The third cause of the Toyota Code P0139 is a malfunction of the ECM. This can be caused by coding errors or other issues with the engine control unit. To repair this issue, the programming must be checked and the ECM must be replaced if needed.
Fuel Cut
The fourth cause of the Toyota Code P0139 is a malfunction of the fuel cut system. This can be caused by issues with the fuel cut system itself or other related components. To repair this issue, the fuel cut system must be checked and verified to be functioning correctly.
Conclusion: Troubleshooting Toyota Code P0139
The Toyota Code P0139 is a fault code that indicates an issue with the oxygen sensor circuit slow response (Bank 1 Sensor 2). There are several common causes of this issue, including a short in the HO2 sensor circuit, a faulty HO2 sensor, or a malfunction of the ECM. It is important to properly diagnose and repair the Toyota Code P0139, as outlined in the related service bulletin G0G. By understanding the causes and solutions associated with this code, it is possible to quickly and effectively troubleshoot and repair any issues.
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