Fault code P1423 – a step-by-step guide to diagnosing and fixing it

Error code P1423 is displayed and the check engine light is on - what does this mean?

The DTC P1423 is a manufacturer-specific fault code that is recognized by the OBD system and typically indicates problems with the secondary air system. In most vehicles, this trouble code refers to a malfunction of the secondary air pump or its control circuit. Depending on the manufacturer, the exact definitions may vary, with BMW, Audi and Volkswagen having different interpretations.

What causes can this fault code have?

• Defective secondary air pump
• Damaged or clogged secondary air lines
• Defective secondary air switching valve
• Broken or damaged cables in the control circuit
• Loose or corroded plug connections
• Defective secondary air pressure sensor
• Clogged air filter of the secondary air pump
• Faulty engine control unit software

What symptoms occur in parallel with error code P1423?

• Starting problems: Extended starting time when the engine is cold
• Increased emissions: Poorer exhaust gas values, especially during the warm-up phase
• Unsteady idling: Engine runs unevenly after a cold start
• Check engine light: Permanent display of the warning light on the dashboard
• Loss of power: Reduced engine power during the first few minutes after starting
• Unusual noises: Whistling or humming noises from the engine compartment

How to fix the problem of error code P1423?

• Repairing EOBD error code P1423 requires a systematic approach to identifying and eliminating the cause.
• Replace the secondary air pump: Complete replacement of the defective pump including seals and mounting hardware
• Clean or replace secondary air lines: Flush out clogged lines or replace completely if damaged
• Repair the switching valve: Replace defective secondary air switching valve with a new original part
• Repair electrical connections: Check all cables and plug connections, clean and replace if necessary
• Calibrate pressure sensor: Recalibrate secondary air pressure sensor or replace if defective
• Carry out a software update: Program the engine control unit with the latest firmware and delete the fault memory