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Bmw 318Is Secondary Air Injection Relays

Bmw 318Is Secondary air injection relays

Starting at $23.95, AutoBuffy stocks 1 secondary air injection relays from Standard Ignition to fit the Bmw 318Is. This relay controls power to the air pump that pushes fresh air into the exhaust during cold starts, reducing harmful emissions. When it fails, the pump won't activate, triggering check engine lights and immediate smog test failure.

Signs your Bmw 318Is needs a new secondary air injection relay

  • Check engine light on with stored codes P0410, P0411, P0412, P0413, or related secondary air injection fault codes
  • Air injection pump never runs during cold start — no audible hum or whoosh from the pump in the first 30–90 seconds after startup
  • Failed emissions or smog inspection due to secondary air system not functioning
  • Air pump runs continuously and won't shut off after the engine warms up, pointing to a stuck-closed relay contact
  • Relay clicks or chatters repeatedly at startup instead of holding a steady connection
  • Fusible link or fuse for the air injection circuit blows repeatedly because the relay is passing excessive current

Which secondary air injection relay should you buy for your Bmw 318Is?

The secondary air injection relay is a straightforward electrical component, but quality matters because it switches high current loads to the pump motor every cold start. Your main decisions are whether to buy OE-equivalent or premium aftermarket, and whether you need a standalone relay or a relay-and-socket assembly. Always confirm the relay's amperage rating and connector type match the Bmw 318Is's fuse box or relay bracket.

OE-Equivalent Replacement
Best for
Restoring factory reliability at a moderate price
What you get
Matching amperage rating, identical pin configuration, and plug-and-play fit — no wiring modifications needed
Premium / Heavy-Duty Relay
Best for
High-mileage vehicles or extreme climates where relays fail repeatedly
What you get
Upgraded contact material and sealed housing resist heat, vibration, and moisture better than standard units
Relay + Pigtail Harness Kit
Best for
Vehicles where the relay socket or wiring has burned or corroded
What you get
New relay plus a pre-terminated connector so you repair both the relay and any damaged wiring in one step
Relay Assortment / Universal
Best for
DIYers who want spares on hand or are unsure of the exact relay spec
What you get
One or more relays with common pin layouts; requires careful spec matching to confirm amperage and coil voltage match factory requirements

Secondary air injection relays brands we stock for your Bmw 318Is

Standard Ignition
1 option · from $23.95

Replacing the secondary air injection relay on a Bmw 318Is

Easy⏱ 15–30 minutesFuse puller or needle-nose pliersDigital multimeterFlashlight or work lightOwner's manual or underhood fuse box diagram

Locate the secondary air injection relay in the underhood fuse and relay center using the cover diagram or owner's manual, then pull the old relay straight out and press the new one firmly into the same socket until it seats. After installation, clear any stored fault codes with a scan tool and perform a cold-start drive cycle to confirm the air pump activates and no codes return. No special torque specifications are required since the relay simply plugs in.

Frequently asked questions

How much does it cost to replace secondary air injection relays on a Bmw 318Is?
The part itself starts at $23.95 at AutoBuffy, making it one of the more affordable fixes in the secondary air system. A shop will typically charge a small amount of diagnostic and labor time on top of the part cost since the relay is usually accessible in the underhood fuse and relay box, keeping total repair costs relatively low.
Can a bad secondary air injection relay cause a check engine light on a Bmw 318Is?
Yes. A failed relay prevents the air pump from receiving power, so the engine control module detects no airflow in the exhaust during the cold-start test cycle and sets a fault code — most commonly in the P0410–P0418 range. Clearing the code without replacing the relay will only result in the light returning within one or two drive cycles.
How do I test the secondary air injection relay on my Bmw 318Is before buying a new one?
Remove the relay and apply 12 V directly across the coil terminals — pins 85 and 86 on a standard ISO mini relay. You should hear a click and measure continuity across the switched terminals (pins 30 and 87). No click, no continuity, or a relay that stays closed with no power applied all confirm the relay has failed and needs replacement.
Will a bad secondary air injection relay cause my Bmw 318Is to fail emissions testing?
Yes, almost certainly. Emissions inspectors check for active fault codes and may perform a functional test of the secondary air system. A failed relay means the pump never runs, the system never passes its self-test, and a fault code is stored — any one of these conditions is enough to fail a smog check in states that require it.
Is the secondary air injection relay the same as the air pump fuse on a Bmw 318Is?
No — they are separate components. The fuse protects the circuit from overcurrent and is a one-time sacrificial link. The relay is an electromechanical switch the ECM uses to turn the pump on and off on command. Both should be inspected when diagnosing a secondary air system fault, because a failed relay can cause repeated fuse failures if its contacts weld shut.
How long does a secondary air injection relay last on a Bmw 318Is?
Relay lifespan varies widely based on climate, electrical system health, and how often the vehicle is cold-started. In general, relays last many years under normal conditions, but repeated exposure to heat from a nearby engine component, voltage spikes, or a struggling air pump that draws excess current can shorten service life considerably. Replacement is inexpensive enough that it is a reasonable first step when diagnosing air injection faults.

Shop secondary air injection relays by year for the Bmw 318Is

19991998199719961995199419931992

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Secondary air injection relays for other Bmw models

Bmw 325iBmw 328isBmw 323isBmw 323iBmw M5Bmw 335xi