Why is the “Check Engine / Emission System” light coming on in my Land Rover?

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Why is the “Check Engine / Emission System” light coming on in my Land Rover?

My Land Rover e.g., Discovery, Range Rover, Defender frequently shows the check engine o r emissions warning light even when it still runs seemingly fine. This often happens after refueling o r during city driving in Pakistan. What are the most common emission‑related causes like oxygen sensor faults, EVAP leak, catalytic converter issues, etc., and how can I diagnose which component is triggering the light? What typical sensor codes should I look for with an OBD‑II scan?

Talha Kyanii asked on 11 Dec 2025 13:21:47 pm

1 Answer

6 views |

Gari Master - on 11 Dec 2025 13:23:05 pm

The check engine/emission warning light usually comes on due to a problem in the engine’s emission control system. Common causes in Pakistan include:

Faulty oxygen O₂ sensors: These sensors measure exhaust oxygen levels. If they fail, the ECU can’t regulate fuel properly, causing high emissions.

EVAP system leaks: A loose fuel cap, cracked hoses, o r faulty purge valves can let fuel vapors escape, triggering the light.

Catalytic converter issues: A worn-out o r clogged converter can’t clean exhaust gases effectively.

Faulty mass air flow MAF sensor: Sends wrong air intake data to the ECU, affecting fuel mixture and emissions.

Diagnosis & Solution:

Use an OBD-II scanner to check the error codes. Codes like P0420 Catalytic Converter Efficiency, P0171/P0172 Lean/Rich Fuel, o r P0130-P0167 O₂ sensors are common.

Inspect fuel system hoses and cap for leaks.