P0418 on Lexus
Secondary Air Injection System Relay A Circuit
P0418 on Lexus vehicles indicates secondary air injection system relay a circuit. Au7o has documented this code across 1 Lexus model — most commonly on GX. This code means the Engine Control Module detected a fault in the control circuit for Secondary Air Injection (AIR) System Relay 'A'. The secondary air injection system pumps fresh air into the exhaust during cold starts to help the catalytic converter heat up faster and burn off pollutants, and Relay A switches power to that air pump. P0418 sets when the computer commands the relay but sees an abnormal voltage or no response on its control circuit. This is an emissions-related fault that may keep the air pump from running when needed.
Common Causes of P0418
- •Faulty secondary air injection relay (Relay A)
- •Open, shorted, or corroded relay control wiring
- •Poor power or ground feed to the relay
- •Failed secondary air injection pump (drawing wrong current)
- •Corroded relay socket or connector
- •Blown fuse in the air injection circuit
- •Faulty ECM relay driver
P0418 on Lexus by Model
Lexus GX(1 issue)
- Secondary Air Injection System Failure Causing Limp Mode on GX 4602010-2013
The secondary air injection system pumps air into the exhaust on cold start to light the catalysts faster. On the GX 460 it fails in two related ways. The foam filter inside the air injection pump disintegrates with age and the debris is drawn into the system, blocking the air switching valves and lines downstream. Separately, and in the large majority of failures, the diverter or air switching valve corrodes from moisture contamination. Either failure sets emissions codes and drops the vehicle into limp mode, which owners experience as a sudden dramatic loss of power on a cold morning, usually on the first drive of the day. Lexus acknowledged the defect for 2010-2013 GX 460 vehicles with the 1UR-FE engine in a Special Service Campaign (bulletin L-SB-0028-14) covering MIL-on conditions with DTC P0418, P2440, P2442 and/or P2445, under which the pump filter and air switching valves are replaced at no charge. This is the same architecture that troubles the 2010-2013 Tundra, Sequoia, and LX 570.
Looking for P0418 on a different make?
View P0418 across all makes →Frequently Asked Questions
What does P0418 mean on Lexus?▼
P0418 stands for "Secondary Air Injection System Relay A Circuit." This code means the Engine Control Module detected a fault in the control circuit for Secondary Air Injection (AIR) System Relay 'A'. The secondary air injection system pumps fresh air into the exhaust during cold starts to help the catalytic converter heat up faster and burn off pollutants, and Relay A switches power to that air pump. P0418 sets when the computer commands the relay but sees an abnormal voltage or no response on its control circuit. This is an emissions-related fault that may keep the air pump from running when needed. On Lexus specifically, this code is documented across 1 model.
What causes P0418 on Lexus vehicles?▼
Common causes on Lexus: Faulty secondary air injection relay (Relay A), Open, shorted, or corroded relay control wiring, Poor power or ground feed to the relay, Failed secondary air injection pump (drawing wrong current), Corroded relay socket or connector. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0418 on a Lexus?▼
Repair costs vary widely depending on the root cause and specific Lexus model.
Which Lexus models have P0418 documented?▼
Au7o has documented P0418 on 1 Lexus model: GX.