MIL ON - DTC P0420, Catalyst Efficiency.
ENGINEEG002-99
REVISED
Title:
DIAGNOSTIC TROUBLE CODE P0420
Models:
'99 Sienna
June 11, 1999
Introduction
The following information is intended to assist in the diagnosis of DTC P0420 indicating a possible Catalyst System Efficiency Below Threshold condition.
Affected Vehicles
^ 1999 Sienna
Warranty Information
Applicable Warranty *:
This repair is covered under the Toyota Basic Warranty. This warranty is in effect for 36 months or 36,000 miles, whichever occurs first, from the vehicle's in-service date.
Coverage is extended to 36 months or 50,000 miles, whichever occurs first, in the states of California and Massachusetts under the California Emission Warranty.
* Warranty application is limited to correction of a problem based upon a customer's specific complaint.
NOTE:
Please enter the DTC P0420 in the Condition/Cause/Remedy Section when applying for Warranty Reimbursement.
Repair Procedure
Should a MIL "ON" condition with DTC P0420 be encountered, perform the diagnostic procedures described in the Repair Manual.
If the problem source cannot be identified after checking all affected areas in the Repair Manual, the cause may be an incorrectly assembled wiring harness. Only if all affected areas in the Repair Manual check good, should the following repair procedure be used.
Using the Scantool with the vehicle running and at operating temperature, access the 02 Sensor RPM check and pull up the Rear 02 Sensor data. It should show an abnormal square wave signal as illustrated in Chart 1.
Proceed by accessing the E11 (D) Connector at the ECU. Using a jumper wire connected to a known good ground point, back probe E04 (Pin 1) at the connector. If the Rear 02 Sensor signal changes from a square wave signal to a flat line signal, switch E05 (Pin 8) and E1 (Pin 17) in the E11 (D) Connector.
If the signal does not change back probe E05 (Pin 8). If the signal then changes from a square wave signal to a flat line signal, switch E04 (Pin 1) and E1 (Pin 17) in the E11 (D) Connector. After repairs are made, the Rear 02 Sensor signal should be a flat line signal as illustrated in Chart 2.