2002 Toyota Sienna 2002 Toyota Sienna fault code P0420

I say it could be the ECM, this is the tech bulliten on it.
Reference Number(s): EG047-05, Â Date of Issue: Â October 19, 2005 Related Ref Number(s): EG047-05 ARTICLE BEGINNING INTRODUCTION Under certain driving conditions, some 2001 - 2003 model year Sienna vehicles may exhibit a M.I.L. "ON" with the following DTC: Ã Â Â P0420 (Catalyst System Efficiency Below Threshold [Bank 1]) The Engine Control Module (ECM) (SAE term: Powertrain Control Module/PCM) logic has been modified to improve this condition. APPLICABLE VEHICLES Ã Â Â 2001 - 2003 model year Sienna vehicles. PARTS INFORMATION PARTS INFORMATION WARRANTY INFORMATION WARRANTY INFORMATION Applicable Warranty*: This repair is covered under the Toyota Federal Emissions Warranty. This warranty is in effect for 96 months or 80,000 miles, whichever occurs first, from the vehicle's in-service date. TOYOTA: 2001 - 2003 Sienna SECTION: ENGINE PREVIOUS PART NUMBER CURRENT PART NUMBER PART NAME QTY 89661-08061 89661-08062 Module, Engine Control 1 89661-08070 89661-08071 89661-08080 89661-08081 OP CODE DESCRIPTION TIME OFP T1 T2 895011 R & R Engine Control Module 0.5 89661-08061 89661-08070 89661-08080 8A 71REPAIR PROCEDURE 1. Verify DTC P0420 with the Diagnostic Tester by referring to the Technical Information System (TIS), 2001 - 2003 model year Sienna Repair Manual: Diagnostics: Engine: Pre- Check. 2. Replace ECM (PCM). Follow the Repair Manual ECM replacement instructions. Refer to TIS, 2001 - 2003 model year Sienna Repair Manual: Introduction: How To Troubleshoot ECU Controlled Systems: How To Use The Diagnostic Chart And Inspection Procedure. 3. Perform the following steps to confirm that the vehicle is repaired. A. Reset the Readiness test by using the "Clear DTC" function on the Diagnostic Tester. Ã Â Â To clear the DTC, refer to TIS, 2001 - 2003 model year Sienna Repair Manual: Diagnostics: Engine: Pre-Check. B. Perform Readiness Monitor Drive Patterns for Catalyst Monitor O2S type and AF Sensor type. Refer to TSB No. EG003-02, "Readiness Monitor Drive Patterns, " procedures: Catalyst Monitor (O2S Type) and Catalyst Monitor (AF Sensor Type). C. If a DTC is set during the above drive patterns, refer to the Diagnostic Trouble Code Chart in TIS, 2001 - 2003 model year Sienna Repair Manual: Diagnostics: Engine: Diagnostic Trouble Code Chart. Test drive the vehicle to confirm normal operation.