Fault code P1187 – a step-by-step guide to diagnosing and fixing it

Error code P1187 is displayed and the check engine light is on - what does this mean?

The DTC P1187 is a manufacturer-specific fault code that is recognized by the OBD/EOBD diagnostics and indicates a problem with the fuel system. This trouble code mainly concerns the fuel-air mixture and the mixture control. This fault code can have different meanings for different manufacturers, but usually refers to a mixture composition that is too lean.

What causes can this fault code have?

• Defective lambda sensor or O2 sensor
• Clogged or defective fuel filter
• Damaged fuel pump
• Leaks in the intake system
• Defective mass air flow sensor (MAF)
• Clogged fuel injectors
• Defective fuel pressure regulating valve
• Cracks or damage in vacuum lines
• Faulty engine control unit (ECU)
• Loose or corroded plug connections

What symptoms occur in parallel with fault code P1187?

• Engine performance: Noticeable loss of power and uneven engine running
• Fuel consumption: Increased consumption despite lean mixture composition
• Starting behavior: Difficulties with cold starts or longer starting times
• Idle problems: Irregular or excessive idling
• Exhaust behavior: Increased emission values during the emissions test
• Jerking: Vehicle jerks especially at low engine speeds

How can the problem with error code P1187 be rectified?

• Repairing EOBD error code P1187 requires a systematic approach to identify the exact cause.
• Check the lambda sensor and replace if defective, as it is essential for correct mixture control
• Replace fuel filter and test fuel system for continuity and correct pressure
• Clean or replace the mass air flow sensor if the measured values are out of specification
• Check the intake system for leaks and replace damaged hoses or seals
• Clean fuel injectors professionally or replace if heavily soiled
• Check vacuum lines for cracks and replace defective lines
• Check electrical connections and clean or replace corroded plugs