AutoCodes – Generic – P1138

P1138 Code - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich

Quick Answer

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, Heated Oxygen Sensor 2 Bank 1 harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1138 indicates Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich.
Common causes: Common causes include Exhaust gas leaks, Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1, Heated Oxygen Sensor 2 Bank 1 harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 34,902

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 24, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1138 Description

The Heated Oxygen Sensor 2 (HO2S2) (Downstream), after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air-fuel mixture (air-fuel ratio) must maintain near the ideal stoichiometric ratio. The HO2S2 output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Powertrain Control Module (PCM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S2 generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The PCM interprets Lean when the HO2S2 voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The PCM interprets Rich when the HO2S2 voltage is above 0.45 V. The P1138 code will set when the PCM detects that the HO2S2 signal is above the voltage of range for an extended period.

OBDII Code P1138 - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich - AutoCodes.com — P1138 Code - Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich

What does this mean?

What are the Possible Causes of the DTC P1138?

Exhaust gas leaks
Faulty Heated Oxygen Sensor 2 (HO2S2) (Downstream) Bank 1
Heated Oxygen Sensor 2 Bank 1 harness is open or shorted
Heated Oxygen Sensor 2 Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors

How to Fix the DTC P1138?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1138 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1138 code?

Need more information on how to fix the P1138 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1138 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1138 Audi — Long Term Fuel Trim Add. Fuel B2 System Too Lean
P1138 BMW — O2 Sensor Heater Circuit Low Voltage Bank 1 Sensor 2
P1138 Buick — HO2S Circuit High Voltage Sensor 2
P1138 Cadillac — HO2S Circuit High Voltage Sensor 2
P1138 Chevrolet — HO2S Circuit High Voltage Sensor 2
P1138 Ford — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 GMC — HO2S Circuit High Voltage Sensor 2
P1138 Infiniti — Swirl Control Valve Control System Performance
P1138 Isuzu — HO2S 2 Voltage Stays High Rich Condition
P1138 Lincoln — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 Mazda — Rear O2 Sensor Self Test Fault
P1138 Mercury — Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich
P1138 MINI — O2 Sensor Heater Circuit Low Voltage Bank 1 Sensor 2
P1138 Nissan — Swirl Control Valve Control System Performance
P1138 Pontiac — HO2S Bank 1 Sensor 2 Rich or High Voltage
P1138 Saturn — HO2S Bank 1 Sensor 2 Rich or High Voltage
P1138 Suzuki — HO2S Circuit High Voltage During Decel Fuel Cut-Off Sensor 2
P1138 Volkswagen — Long Term Fuel Trim Add. Fuel B2 System Too Lean

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P1138 Code

1. What are the common symptoms of OBDII code P1138?

- Common symptoms include decreased fuel efficiency, rough idling, and a noticeable decrease in engine performance.

2. What are the possible causes of OBDII code P1138?

- The code may be triggered by a faulty oxygen sensor, a vacuum leak, a fuel system issue, or a problem with the engine's air intake system.

3. How can I diagnose the root cause of OBDII code P1138?

- To diagnose the issue, you can use an OBDII scanner to read the code and then perform a visual inspection of the oxygen sensor, vacuum lines, and air intake system.

4. What does it mean when the code P1138 indicates "Lack Of Heated Oxygen Sensor Switches Bank 1 Sensor 2 Switch Indicates Rich"?

- This means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting a rich air-fuel mixture.

5. Can I drive with OBDII code P1138 present in my vehicle?

- It is not recommended to drive with this code present, as it can lead to further damage to the engine and the catalytic converter.

6. How do I repair OBDII code P1138?

- The repair process typically involves replacing the oxygen sensor on bank 1 sensor 2 and addressing any underlying issues such as vacuum leaks or fuel system problems.

7. Are there any DIY tips for fixing OBDII code P1138?

- While replacing the oxygen sensor may require some mechanical skill, checking for vacuum leaks or loose connections in the air intake system is something that can be done by a DIY enthusiast.

8. Can a dirty air filter cause OBDII code P1138 to appear?

- Yes, a dirty air filter can disrupt the air-fuel mixture ratio and potentially trigger code P1138, so it's important to check and replace the air filter if necessary.

9. How long does it typically take to repair OBDII code P1138?

- The repair time can vary depending on the exact cause of the code, but replacing the oxygen sensor usually takes around 1-2 hours.

10. Will resetting the OBDII code P1138 make it go away permanently?

- Resetting the code may temporarily turn off the check engine light, but if the underlying issue is not fixed, the code is likely to reappear. It's important to diagnose and repair the root cause of the problem.