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2001 Toyota Sienna P0420 P0430 Oxygen Sensor Malfunctions - Help!
 
                    

Replacing the Oxygen Sensors on a Toyota Sienna Van - 2001 
1/26/06 1MZ-FE V6 

The P0420 & P0430 DTC Error codes seemed to suggest that the catalytic converters were bad, but instead the oxygen sensors were the problem. And, of course, being heated ones, they cost over $100 each. What happens is, the deteriorating sensors make the computer (ECM) increase the richness of the mixture to a point that the converters cannot work well. Here we go again. I knew this was going to cost some money from the start.

Words of Warning - You have to get right under the vehicle to do these replacements. Please don't let it fall on you! Jack Stands and other safety measures are recommended.

Oxygen Sensor Part Numbers Toyota Sienna 2001 
Bosch Oxygen Sensor Part Numbers - 2 Near engine are 13540 Rear Oxygen Sensor is 13566
Note: They use different connectors! (Something no one could ever confirm until I pulled them out)

Changing the front one is easy... the other 2 are mind numbingly difficult! Pictures to follow soon.
The rear one is easy enough to pull down, but the connector is under the front passenger seat and hard to reach of course. The firewall one ( the middle one if you like) is the real challenge. I used all kinds of tools to unscrew it and replace it. Although it is in plain sight, it is completely "boxed in" by the axles and other stuff in a way that is almost funny when you start to try to remove it!

PLEASE NOTE: After you replace them and clear the codes with your scanner (I use a CP9135 by www.Actron.com) you will have to drive a while to reset (make "Ready") the Oxygen and Catalyst Readiness Monitors.

My "EVAP Readiness Monitor" NEVER did go "Ready" but the State Inspection folks (Texas) know this happens sometimes and make allowances for having no more than 2 of these monitors not set (as long as no other emission  DTC codes are present of course). It passed. Check your states rules on this - we wasted 3 weeks worrying about it when we could have had it inspected and passed!
 
The lesson? If you are buying a 1999-2003 Toyota Sienna (or many other  cars of these years too probably), budget for new oxygen sensors and they will be expensive. By the time we finished, we were out $500 and we did the work ourselves. Goodness knows what a garage would charge.

 

You can see the easy one sticking out of the front exhaust manifold (look above the "1MZ" in 1MZ-FE)

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