P0418

Secondary Air Injection System Control "A" Circuit

Car Fault Codes Emissions & exhaust

Can you still drive? Yes, normally

Who can fix it? Needs a workshop

Typical repair time 15 minutes – 3 hours

Typical cost SAR 50 to 2,000

What it means

The engine computer has detected an electrical fault in the control circuit it uses to run the secondary air pump, which on most vehicles is the pump relay circuit. The pump then does not run at cold start, or it may run constantly if the relay sticks.

Symptoms4

Check engine light on.
No pump sound after a cold start.
Pump keeps running after the cold-start period if the relay is stuck.
Failed emissions test.

Possible causes5

Failed secondary air pump relay.
Blown fuse for the pump or relay.
Open or shorted wiring in the control circuit.
Failed pump drawing excessive current and damaging the relay or fuse.
Faulty driver circuit inside the engine computer (rare).

How to diagnose5

Check the fuse and swap the relay with an identical known-good one if the box has one.
Command the relay with a scan tool and listen for it to click.
Check voltage at the relay coil and the control signal from the computer.
Inspect the circuit wiring for opens or shorts.
If the fuse keeps blowing, check the pump, which may be seized or shorted.

How to fix5

Replace the blown fuse or faulty relay.
Repair the control circuit wiring.
Replace the pump if it draws excessive current and damages the relay.
Check the check valve when replacing the pump to stop moisture getting in again.
Clear the codes and recheck after a cold start.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is small when a relay or fuse is to blame, and rises if the pump itself turns out to be damaging the circuit.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Is replacing the relay enough?

Usually, but if the new relay fails or the fuse blows again, the pump is likely drawing too much current and must be checked.

Is it harmful if the pump runs all the time?

Yes. If the relay sticks, the pump can run constantly, overheat and fail, so fix it promptly.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

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