Possible Causes

1. Exhaust gas leaks
2. Faulty Heated Oxygen Sensor 2 (HO2S2) (downstream), Bank 1
3. Open or short circuit in Bank 1 Heated Oxygen Sensor 2 wiring harness
4. Poor electrical connection in Heated Oxygen Sensor 2 circuit, Bank 1
5. Inappropriate fuel pressure
6. Faulty fuel injectors

How to Fix MERCURY Code P1137?

Start by checking the possible causes listed above:

• Visually inspect the wiring harness and corresponding connectors.
• Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

Possible Symptoms

• Check Engine Light on (or Service Engine Soon warning light)

Meaning of MERCURY Code P1137

The Heated Oxygen Sensor 2 (HO2S2), located after the three-way catalyst (manifold), monitors the oxygen level in the exhaust gases on each engine bank.

For optimal catalyst operation, the air-fuel ratio must remain close to the ideal stoichiometric ratio. Here’s how it works:

• The HO2S2 generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gases.
• If oxygen in the exhaust gases increases, it indicates a lean mixture. The PCM interprets this when the HO2S2 voltage is below 0.45 V.
• If oxygen in the exhaust gases decreases, it indicates a rich mixture. The PCM interprets this when the HO2S2 voltage is above 0.45 V.

The PCM then adjusts the fuel injection time to maintain an air-fuel ratio as close as possible to the optimal stoichiometric ratio.

The P1137 code on MINI vehicles indicates an intermittent signal from the heater circuit of the post-catalyst oxygen sensor (O2) (Bank 1, Sensor 2). This sensor monitors the catalyst’s efficiency and adjusts the air-fuel mixture. A heater malfunction prevents the sensor from reaching its optimal operating temperature, skewing the data.

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Common Symptoms

• Check Engine Light on (code P1137 and sometimes P0136-P0138).
• Unstable idle or vibrations.
• Increased fuel consumption (up to +15%).
• Reduced performance during acceleration.

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Main Causes

Category	Details
Faulty O2 Sensor	Heater resistance out of specifications (typically 5–20 Ω when cold).
Electrical Issues	Cut wires, short circuit, corroded or disconnected connector.
Blown Fuse	Heater circuit fuse (often in the passenger fuse box).
ECM Failure	Interrupted heater control signal.

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Diagnostic Steps

1. Locate the O2 Sensor (Bank 1, Sensor 2)

• Location: On the exhaust line, after the catalyst, on the cylinder #1 side (for 4-cylinder MINIs, left side).

2. Inspect Wiring and Connector

• Look for: Chafed, burnt wires, or corroded connector (especially near the exhaust).
• Continuity Test: Check for no breaks between the sensor and the ECM.

3. Test Heater Resistance

• Disconnect the sensor and measure resistance between the heater terminals (usually 2 wires of the same color).
  • Expected: 5–20 Ω at room temperature.
  • Out of specs → Replace the sensor.

4. Check Power and Ground

• Power Supply Voltage: Engine off, measure 12V between the power wire and ground (with ignition in ON position).
• Fuse: Check the dedicated fuse (e.g., F57 on MINI Cooper R56).

5. Analyze with an OBD2 Scanner

• Live Data: Check the O2 sensor voltage (should oscillate between 0.1–0.9 V in closed loop).
• Related Codes: If P0037 is present, prioritize repairing the heater circuit.

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Solutions and Costs

Problem	Solution	Cost (€)
Faulty O2 Sensor	Replace with an OEM part (e.g., Bosch 0258006031).	80–200
Damaged Wiring	Repair the harness or replace the connector.	30–150
Blown Fuse	Replace (5–10 A, depending on model).	5–15

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Best Practices

• Use penetrating oil to remove the O2 sensor (risk of corrosion on the exhaust).
• Reset the ECM after repair to clear adaptations.

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FAQ

Q: Can I drive with a P1137 code?
A: Yes, but avoid long trips. A cold sensor increases emissions and wears out the catalyst.

Q: Why does the code come back after replacing the sensor?
A: Check the wiring or fuse. A persistent short circuit can damage the new sensor.

Pro tip: On MINI Cooper S models (R53/R56), prefer NGK or Bosch sensors for optimal compatibility. Use an INPA or ISTA+ tool for in-depth diagnosis.

Possible Symptoms

🚨 Code P1138 on 1997 Ford F150: Causes, Symptoms & Solutions

🔍 Meaning of Code P1138

Code P1138 on a 1997 Ford F150 indicates a problem with the Heated Oxygen Sensor 2 (HO2S2) located downstream of the catalytic converter (Bank 1). This sensor monitors the catalytic converter’s efficiency by measuring the oxygen level in the exhaust gases. An abnormal voltage (outside the 0.1–0.9 V range) indicates an air-fuel mixture that is too rich (>0.45 V) or too lean (<0.45 V), preventing the PCM from correctly regulating fuel injection.

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⚠️ Severity of Code P1138

Urgency Level: 🟠 Medium (Address within 1-2 weeks).

• Risks:
• Increased fuel consumption.
• Damage to the catalytic converter.
• Failure of emissions inspection (excessive pollutants).

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🚨 Common Symptoms

• ✅ Check Engine Light illuminated.
• 🐌 Hesitant acceleration or loss of power.
• ⛽ Increased fuel consumption.
• 💨 Gasoline smell or exhaust smoke.

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🔧 Possible Causes

1. Exhaust leaks: Cracks in the manifold or catalytic converter.
2. Faulty HO2S2 sensor: Wear, soot contamination.
3. Electrical issues: Damaged wiring, corroded connectors.
4. Incorrect fuel pressure: Faulty regulator or pump.
5. Stuck injectors: Leaking or clogging.

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🛠️ Diagnostic and Repair Steps

1. Inspect for Exhaust Leaks

• 🔍 Use smoke or soapy water to locate leaks.
• Critical areas: Manifold gaskets, pipes, catalytic converter.

2. Test the HO2S2 Sensor

• 🔌 Disconnect the connector and measure resistance (compare to factory values).
• 🔋 Measure voltage with the engine running (expected 0.1–0.9 V).

3. Check Wiring and Connectors

• 🔎 Look for cut wires, corrosion, or bent pins.
• 🧼 Clean connectors with contact cleaner spray.

4. Check Fuel Pressure

• ⛽ Use a mechanical gauge (expected value: 35–45 psi).
• 🔄 Replace the fuel pressure regulator or pump if necessary.

5. Inspect Injectors

• 🔧 Test injector resistance (≈12–16 Ω).
• 🧴 Use injector cleaner or replace if faulty.

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💰 Estimated Costs

Service	Cost (USD)
HO2S2 sensor replacement	80 – 150
Exhaust leak repair	100 – 300
Injector replacement	50 – 200 (per unit)
Professional diagnosis	50 – 100

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❓ FAQ: Frequently Asked Questions

Q: Can I drive with code P1138?
→ A: Yes, but avoid long trips to protect the catalytic converter.

Q: Can code P1138 clear itself?
→ A: No, unless the fault is intermittent (e.g., temporary bad connection).

Q: Why check fuel pressure?
→ A: Incorrect pressure skews the O2 sensor data.

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🚗 Conclusion: Take Action to Protect Your Engine

An unresolved P1138 code can lead to:

• Catalytic converter overheating (replacement cost: $500–2000).
• Decreased engine performance.
• Excessive pollutant emissions.

🔧 Pro Tip: Choose an OEM O2 sensor for optimal compatibility.

What is the P1138 code on an Audi?

The P1138 trouble code on Audi vehicles generally corresponds to a problem with a too-lean fuel mixture in the Fuel System B2. However, the precise description of this code may vary depending on the model and year of the vehicle.

If this code appears on your dashboard, it is essential to quickly diagnose and correct the underlying cause to avoid potential engine damage.

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Possible causes of the P1138 code on Audi

The P1138 code can be triggered by several factors, including:

• Intake air leak: An uncontrolled air intake leads to a too-lean air/fuel mixture.
• Faulty O2 sensor: A malfunctioning oxygen sensor can send incorrect readings to the ECU.
• Faulty Mass Air Flow (MAF) sensor: A bad signal from the MAF can distort the air/fuel mixture calculation.
• Damaged O2 sensor wiring harness: An open or short-circuited wire can cause sensor malfunction.
• Poor electrical connection in the O2 sensor circuit: Loose, corroded, or damaged connectors can cause reading errors.

Possible symptoms of the P1138 code

• Check Engine Light illuminated on the dashboard
• Excessive fuel consumption
• Engine starting difficulties
• Engine misfires
• Sluggish or jerky acceleration
• Increased pollutant emissions

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How to fix the P1138 code on Audi?

1. Check for possible causes

• Visually inspect the air intake system for leaks (cracked hoses, loose clamps, etc.).
• Check the condition of the O2 sensor (lambda probe) and the MAF sensor.
• Examine the O2 sensor wiring harness for broken, bent, or corroded wires.
• Ensure the circuit connectors are properly seated and not damaged.

2. Test and replace faulty components

• Use an OBD-II scanner to clear the code and check if it reappears.
• Replace the O2 sensor if it is faulty.
• Clean or replace the MAF sensor if necessary.
• Repair any air leaks in the intake system.

3. Reset the engine control unit (ECU)

• After performing the repairs, disconnect the battery for 15 to 30 minutes to reset the ECU.
• Reconnect the battery and start the engine to see if the problem persists.

If the Check Engine Light remains on after these steps, it is recommended to consult a qualified mechanic for further diagnosis.

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Conclusion

The P1138 code on an Audi indicates a problem with a too-lean mixture, which can be caused by a faulty sensor or an air leak. It is essential to quickly identify the cause and repair it to avoid more serious engine problems.