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