P0418 Secondary air pump relay A circuit fault

Secondary Air Injection System Relay A Circuit

P0418 in short

P0418 means the engine computer found a fault in the circuit of the relay that powers the secondary air pump. The relay, the pump, a fuse or wiring are the usual causes; on Toyota trucks a wet pump or the air pump driver. You can usually drive, but get it fixed soon, and stop if the pump area smokes.

For a short time after a cold start, some engines blow fresh air into the exhaust so the catalytic converter heats up faster. An electric air pump supplies the air, switched on by a relay (on some Toyota trucks, by an air injection driver module) that the engine computer controls.

P0418 sets when the computer sees that the relay or driver circuit is not behaving as commanded: for example an open or shorted wire, a failed relay, or a pump drawing so much current that the circuit faults.

A relay that sticks on matters more than one that sticks off. Subaru recalled turbo models from 2007 to 2014 because a faulty relay could keep the air pump running until it overheated and smoked.

Most likely causes

  1. Failed air pump relay or air injection driver

    Supported by vehicle data
    Why it ranks here
    KBB lists the pump relay first. Toyota's bulletin for the 2007 Tundra blames the air injection control driver for P0418 and related codes, and Toyota's training case found P0418 pointed to a pump and/or relay fault.
    What would change this
    Rises if the relay does not click or switch power when commanded, or the driver has no output in an active test. Falls if the relay switches power cleanly.

  2. Air pump failed, shorted or damaged by water

    Supported by vehicle data
    Why it ranks here
    Toyota tied P0418 on 2007–2008 Tundra and 2008 Sequoia to water intrusion into the air pump, and Lexus modified the pump filter on the 2010–2013 GX 460. A pump with an open or shorted motor upsets the relay circuit.
    What would change this
    Rises if the pump draws abnormal current, holds water or has an open circuit. Falls if it runs with normal current in an active test.
    How to test the secondary air pump

  3. Blown fuse, damaged wiring or corroded connector

    Common general cause
    Why it ranks here
    KBB lists blown fuses and damaged wiring and connectors. Toyota's training case points to the pump's ground connection near the starter, where water and dirt collect.
    What would change this
    Rises if the pump fuse is blown or a connector is corroded or loose. Falls if the fuse and wiring test good.
    How to test the underhood fuse block (engine compartment fuse box)

  4. Debris from the air pump contaminating the system (Toyota 4.7L)

    Supported by vehicle data
    Why it ranks here
    Toyota's bulletin for 2005–2009 4.7L 4Runner, Land Cruiser, Sequoia and Tundra lists P0418 among air codes caused by debris passing through the air pump.
    What would change this
    Rises on a 2UZ-FE truck with several air codes stored together. Falls on other engines.

  5. Engine computer software

    Possible — needs testing
    Why it ranks here
    KBB says engine computer software is a rare cause.
    What would change this
    Rises if a dealer finds a newer calibration. Falls once the circuit and parts test good and the computer is up to date.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes and freeze-frame data, and note which other air codes are stored (P0419, P2440–P2445).

    Low riskTool: OBD-II scan tool

    • IfSeveral air codes are stored on a Toyota or Lexus truck

      It meansA Toyota or Lexus bulletin may apply.

      Go to step 2

    • IfP0418 is stored alone

      It meansStart with the fuse and relay.

      Go to step 3

  2. Ask a dealer to check the VIN for secondary air bulletins and open recalls, including the Subaru air pump relay recall on turbo models.

    Low riskTool: VIN lookup at a dealer

  3. Check the air pump fuse and relay in the fuse box, and the pump connector and ground for corrosion.

    Low riskTool: fuse tester or multimeter

  4. Have a shop command the pump with a scan tool active test and measure pump current with an amp clamp.

    Best left to a shopTool: scan tool with active tests, amp clamp

    Warning:Run the engine outdoors or with exhaust extraction, keep hands clear of belts and the fan, and do not touch the pump or pipes: they get hot.

Symptoms

  • Check engine light on
  • No air pump sound right after a cold start
  • Limp mode (rare)
  • Air pump keeps running, smokes or smells hot Gets more serious: stop and have it checked.

How to fix

  1. Check the air pump fuse; if it is blown, have the pump checked before fitting a new fuse.

  2. On a 2007–2014 Subaru turbo or a Toyota or Lexus truck, ask a dealer about open recalls and secondary air bulletins first.

Parts and cost context

  • Secondary air pump:If the pump is wet inside, the new one can fail the same way unless the water path is fixed. Labor varies with pump location; get a quote.
  • Underhood fuse block (engine compartment fuse box):The pump relay and fuse usually live in the underhood fuse block; check them before buying a pump.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

  • 2005–2008 · Tundra

    Supported by vehicle data

    2005–2006 4.7L: air system contamination. 2007: air injection control driver. 2007–2008: water in the air pump. Bulletin status not verified.

  • 2005–2008 · Sequoia

    Supported by vehicle data

    2005–2007 4.7L: air system contamination. 2008: water in the air pump. Bulletin status not verified.

  • TSB-0329-08Status unverified

    Air injection pump water intrusion, P0418, P0419 and/or P244x

    2007–2008tundra, sequoia · issued · NHTSA 10033764

    Water gets into the air injection pump.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0029-08Status unverified

    MIL with P0412, P0415, P0418, P0419, P2445 or P2447

    2007tundra · issued · NHTSA 10024894

    May be caused by the air injection control driver.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 02707Status unverified

    MIL with P0418 and/or P2445

    2005–2007tundra, sequoia · issued · NHTSA 10021714

    The flat-file summary gives no cause.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • T-SB-0230-12 RevStatus unverified

    Secondary air injection codes on 2UZ-FE

    2005–20094runner, land-cruiser, sequoia, tundra · 2UZ-FE 4.7L · issued · NHTSA 10132097

    P0418 and other air system codes from debris passing through the air pump.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Lexus

  • 2010–2013 · GX · 1UR-FE

    Supported by vehicle data

    Modified air pump filter and air switching valve assembly. Bulletin status not verified.

  • L-SB-0028-14Status unverified

    MIL with P0418, P2440, P2442 and/or P2445

    2010–2013gx460 · 1UR-FE · issued · NHTSA 10132729

    Air pump filter and air switching valve assembly modified.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Subaru

  • 2007–2014

    Possible — needs testing

    Turbo Legacy and Outback (2007–2009), Impreza (2008–2014) and Forester (2009–2013): recall 16V-738 replaces an air pump relay that can stick on and overheat the pump. The recall does not name P0418; treat it as a lead to check, not a confirmed cause.

    Related recall campaigns: 16V738000

  • P2440Secondary air switching valve stuck open (bank 1)

    Shares causes Supported by vehicle data

    Lexus lists P0418 with P2440 and P2442 on the 2010–2013 GX 460, fixed with a modified pump filter and valve assembly.

  • P2442Secondary air switching valve stuck open (bank 2)

    Shares causes Supported by vehicle data

    Same Lexus GX 460 bulletin: P0418 with P2442 points to the shared pump and filter.

  • P2441Secondary air switching valve stuck closed (bank 1)

    Shares causes Supported by vehicle data

    Toyota's 4.7L bulletin lists P0418 and P2441 together, both from debris passing through the air pump.

  • P0411Secondary air injection flow not as expected

    Primary / secondary Possible — needs testing

    Likely primary: P0418. If the relay never powers the pump, there is no air flow either, so P0411 can follow. Fix the relay circuit first.

All Secondary air injection codes

P0418 questions

Can I drive with P0418?

Usually, yes, for a short while, but get it repaired soon. Stop and switch off if the air pump area smokes or smells burnt.

Is there a recall for P0418?

Subaru recalled 2007–2014 turbo models (16V-738) to replace the air pump relay. The recall does not mention P0418 by name, so have a dealer check your VIN.

Sources and review

  1. P0418 code: secondary air injection system relay A circuit — Kelley Blue Book (KBB Service Advisor, reviewed by Gary Hardesty)
  2. Recall 16V-738 (Subaru WTM-73): secondary air injection pump relay — Subaru of America / NHTSA (read via vehiclesafetyrecalls.com and recallcheck.net) ,
  3. MIL with P0412, P0415, P0418, P0419, P2445 or P2447: air injection control driver (bulletin T-SB-0029-08) — Toyota Motor Sales / NHTSA ,
  4. Toyota Secondary Air System Diagnosis and Repair (TOYOTAtech, November 2020) — AutomotiveTechInfo.com / Toyota Motor Sales ,
  5. Air injection pump water intrusion, MIL with P0418, P0419 and/or P244x (bulletin TSB-0329-08) — Toyota Motor Sales / NHTSA ,
  6. MIL with P0418, P2440, P2442 and/or P2445 (bulletin L-SB-0028-14) — Toyota Motor Sales (Lexus) / NHTSA ,
  7. Secondary air injection codes on 2UZ-FE 4.7L (bulletin T-SB-0230-12 Rev) — Toyota Motor Sales / NHTSA ,
  8. Secondary air injection system incorrect flow detected (P0411) — Rick's Free Auto Repair Advice (Rick Muscoplat) ,
  9. MIL on with P0418 and/or P2445 (Toyota bulletin 02707) — Toyota Motor Sales / NHTSA ,
Last reviewed
Written by
Saurabh K.
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