If you have any questions concerning application or need technical advice concerning your vehicle please give us a call.
We Know Cats!
Everything you need to know about Catalytic Converters.
Discount Converters LTD.
6823 Fulton St.
Houston, Texas 77022
Toll Free USA
888-651-0770
Outside USA
713-722-9200
Fax: 713-691-2071
Toyota Camary, Solara, Sienna DTC PO171 or PO174 Engine Running Lean
Toyota Camary, Solara, Sienna DTC PO171 or PO174 Engine Running Lean
The following Toyota factory bulletin refers to codes P0171 and P0174, lean conditions on either or both banks, but this raises cause for concern when diagnosing catalytic converter codes as well. This bulletin is acknowledging there may be a problem with the Intake Air Control Valves on 2004 Camry, Sienna and Solara vehicles with 3.3L (3MZ-FE) engines.
The same procedure prescribed in this factory publication should be performed before replacing any catalytic converter on one of the affected vehicles. The reason is that this potential vacuum leak may be causing higher than acceptable fuel trims, even if not high enough to set the P0171/P0174 codes which generally appear with fuel trims in excess of 25%. False catalyst codes will often be set when combined fuel trims on either bank approach or exceed 10%. This is because the exhaust gas contains too much oxygen and not enough CO to react with the precious metals on the catalytic converter substrate. In these cases, the substrate may not get to operating temperature, or may cool down during the drive cycle. This will allow the exhaust gas to pass both upstream and downstream O2 sensors “unchanged”, triggering a catalyst code (P0420/P0430). While it is true the catalytic converter was not operating, it would have likely been the fault of the exhaust mixture entering the converter, not the catalyst itself. Correct the mixture and the offending catalytic converter code(s) would very likely disappear as well.