[SOLVED] P1138 Code: Rich Oxygen Sensor Switch – How To Fix It!

Hey there! If you’ve got the engine light or service engine soon warning light on, it could be due to the automobile fault code P1138.

This code usually indicates a problem with the heated oxygen sensor 2 (HO2S2) downstream of bank 1.

The possible causes include exhaust gas leaks, a faulty HO2S2, open or shorted wiring harness, poor electrical connection, inappropriate fuel pressure, or faulty fuel injectors.

To fix this, you’ll need to visually inspect the wiring harness and connectors for any damage, and check for broken, bent, pushed out, or corroded pins in the connectors. It’s important to address this issue as soon as possible to prevent further damage.

The repair time for this can take around 1.0 hour. Hope this helps!

Repair Importance Level10.0 (Out of 10)
Estimated Repair TimeApproximately 1.0 hour
Repair Difficulty Level6.67 (Out of 10)

When the engine light is on or the service engine soon warning light is illuminated, it could be a sign of the p1138 fault code.

  • The symptoms of the automobile fault code P1138 include the Engine Light being ON or the Service Engine Soon Warning Light being illuminated.

The automobile fault code P1138 can be caused by exhaust gas leaks, a faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, open or shorted harness, poor electrical connection, inappropriate fuel pressure, or faulty fuel injectors.

  • The fault code P1138 can be caused by exhaust gas leaks, a faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, an open or shorted harness for Heated Oxygen Sensor 2 Bank 1, a poor electrical connection in the Heated Oxygen Sensor 2 Bank 1 circuit, inappropriate fuel pressure, and faulty fuel injectors.

To fix the automobile fault code p1138, start by visually inspecting the wiring harness, connectors, and components for any damage or corrosion.

  • To fix the automobile fault code p1138, start by checking the possible causes mentioned above.
  • Then, visually inspect the wiring harness and connectors for any damage.
  • Look for broken, bent, pushed out, or corroded pins in the connectors.
  • This fix is estimated to take approximately 1.0 hour.

The factors influencing the cost of diagnosing and fixing the automobile fault code p1138 include the estimated repair time of 1.0 hour and the typical hourly rate charged by auto repair shops, which ranges between $75 and $150.

The P1138 fault code refers to a lack of heated oxygen sensor switches in Bank 1 Sensor 2, indicating a rich air-fuel mixture. The Heated Oxygen Sensor 2 (HO2S2) monitors the oxygen level in the exhaust gas after the three-way catalyst.

It ensures that the air-fuel mixture maintains the ideal stoichiometric ratio for optimal catalyst operation. The PCM adjusts the fuel injection time based on the HO2S2 output voltage, which changes near the stoichiometric ratio. If the HO2S2 voltage is below 0.45 V, the PCM interprets it as a lean air-fuel ratio.

Conversely, if the voltage is above 0.45 V, the PCM interprets it as a rich air-fuel ratio. The P1138 code is triggered when the PCM detects that the HO2S2 signal remains above the voltage range for an extended period. This indicates a lack of switches in the heated oxygen sensor, specifically in Bank 1 Sensor 2, suggesting a consistently rich air-fuel mixture.

What are the possible causes of the automobile fault code P1138?

If you’re seeing the engine light on or the service engine soon warning light, the fault code P1138 could be the culprit. This code can be caused by a few different things, including exhaust gas leaks, a faulty heated oxygen sensor 2 (HO2S2) downstream bank 1, an open or shorted harness for the heated oxygen sensor 2 bank 1, a poor electrical connection in the circuit, inappropriate fuel pressure, or faulty fuel injectors. To fix the issue, start by visually inspecting the wiring harness and connectors, checking for any damage or broken pins.

How can I visually inspect the wiring harness and connectors to fix the P1138 fault code?

If you’re dealing with the P1138 fault code and your engine light is on, it’s time to take action. The culprit could be exhaust gas leaks, a faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, an open or shorted harness, poor electrical connection, inappropriate fuel pressure, or faulty fuel injectors. To fix it, start by visually inspecting the wiring harness and connectors. Look for any damaged components and check for broken, bent, pushed out, or corroded pins on the connectors. Don’t delay, get to the bottom of this issue now!

What should I look for when checking for damaged components and connector’s pins to resolve the P1138 fault code?

If you’re dealing with the P1138 fault code and your engine light is on, it’s important to check for damaged components and connector’s pins. This code can be caused by exhaust gas leaks, a faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, an open or shorted harness, poor electrical connection, inappropriate fuel pressure, or faulty fuel injectors. To fix the issue, visually inspect the wiring harness and connectors, and be on the lookout for broken, bent, pushed out, or corroded pins. Don’t forget to check the “Possible Causes” listed above.

p1138 error fault code explained

If your engine light is on and you’re experiencing issues with your exhaust, it could be due to a few different causes. These include exhaust gas leaks, a faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, an open or shorted harness for Heated Oxygen Sensor 2 Bank 1, poor electrical connection in the circuit, inappropriate fuel pressure, or faulty fuel injectors.

To fix the problem, visually inspect the wiring harness and connectors, checking for any damage or corrosion.

Look out for broken, bent, pushed out, or corroded connector pins.

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