2005-2009 Lexus GX470 and 2006-2007 Lexus LX470 SUVs have a rare (but not albeit unheard of) problem with their secondary air injection system that illuminates the check engine light. Often the truck is down on power or the vehicle makes a booming sound after it is started. The check engine codes that are related to this concern are the following:
- P0412 – Secondary air injection system switching valve “A” circuit
- P0418 – Secondary air injection system system relay “A” circuit
- P1440/P1443 – Secondary air injection system control valve circuit bank 1/bank 2
- P1441/P1444 – Secondary air injection system switching valve number 2 bank 1/bank 2 stuck open
- P2440 Secondary air injection system switching valve stuck open bank 1
- P1442/P1145 Secondary air injection system switching valve number 2 bank 1/ bank 2 stuck closed
- P2441 – Secondary air injection system switching valve stuck closed
The GX470/LX470 secondary air injection system adds fresh air to the exhaust (upstream of the catalysts) during a cold start. The engine runs exceptionally rich upon cold start and the added fresh air helps burn residual fuel. It is an emissions control system that only functions for the first few seconds of a cold start and is important in reducing hydrocarbon emissions.
The system is located entirely under the intake manifold and is hard to access. Here’s the system’s pump and three valves exposed, intake manifold off:
GX470 Air Injection Overview
If you can’t spot the back valves in the above: they are hidden underneath a dual coolant/air crossover pipe also located under the engine’s main rear harness loom (which is plastic and cumbersome).
The cause of the above check engine codes are the pump that distributes debris downstream into the valves. Here’s the pump from a failed unit:
GX470 Air Injection Pump
Where the debris stop is usually the component indicated by the check engine light. The above GX470 had a code for a bank 2 valve stuck open and made a booming noise when started. Here’s a fin sticking the valve open:
GX470 Air Injection Valve
Note that all of the above parts cannot be disassembled for inspection as seen above. Doing so required drilling and cutting of sealed components, so you’re unlikely to track down the exact location of debris without ruining the parts being inspected.
CARspec recommends all secondary air injection parts (pump, all valves, hoses and connectors, and gaskets) be replaced to repair any secondary air injection failures caused by pump debris. Redoing this job twice is hugely labor intensive and debris is easy to miss (because it is hard to inspect everything) so you really want to get it all in the first go.
As Minnepolis, Minnesota’s premier Toyota, Lexus and Scion specialist we see the above more often than most, and can usually have this secondary air injection failure repaired the next business day. If you have a check engine light on your GX470/LX470, don’t hesistate to give us a ring to make an appointment for diagnostics of the above at (952)426-4798 today!
