4th Gen 4Runner: Check engine light with secondary air code, or truck in limp mode

Checks, in order

1. Read the codes
   Scan for P0410 or other air injection codes. Write down the freeze frame and clear them to see if they come back.
   easy $ · under about $50
2. Pump and relay power
   Check the fuse and relay and confirm the pump gets power when commanded at cold start. A silent pump with power is bad.
   medium $ · under about $50
3. Air switching valves and hoses
   Look at the valves and the pipes for water, corrosion and cracks. Moisture in the lines is a common failure path.
   medium $$ · about $50 to $500
4. Replace pump or valve
   Replace the failed part with a quality unit. Bypass kits exist, but they can affect emissions testing where that applies.
   medium $$ · about $50 to $500

Applies to: 2003 to 2009 4Runner with the 4.0L 1GR-FE V6 and the 4.7L 2UZ-FE V8, 2WD and 4WD. Engine specific items are labeled, and some issues apply mainly to early model years.

Tools and parts for these checks

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Go deeper

• Toyota 2UZ-FE 4.7 V8: Specs, Reliability & High Mileage Guide

More 4th Gen 4Runner problems

• V6 losing coolant, cold start misfire or overheating (early 4.0L) (Engine)
• Frame rust or rusted suspension mounts (Frame & Body)
• Clunk, knock or wandering from the front suspension (Steering & Suspension)
• Sticky, melting or cracked dashboard (Body & Electrical)
• V8 timing belt service: when is it due? (Engine)
• Ticking or diesel-like noise on cold start (Engine)

All 16 4th Gen 4Runner symptoms in the interactive troubleshooter →

General guidance from owner experience. Confirm torque specs, fluid capacities and procedures in the factory service manual. Brakes, steering and anything structural: if in doubt, have a qualified shop inspect it before driving.