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2003 Camry
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19 Posts
Discussion Starter · #1 ·
Hi,

I finally got an OBD reader! I checked my 2003 camry, and I got P0420, which means Catalyst Efficiency Below Threshold Bank 1.
My car has about 160k kms on it.

Anyone know what does it mean? I got my emission test done last summer and everything was fine.

Thanks.
 

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'07 XLE 4 cyl.
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6,123 Posts
Use the bloody SEARCH, eh................
 

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イリジウム
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13,823 Posts
P0420 is "Catalyst efficiency below threshold." This means that the ECU, based on the downstream (after catalytic converter) oxygen sensor readings.

The problem is often with oxygen sensors instead of the converter, especially in a properly tuned car (tail pipe blowing zeros). So check for air leaks (for instance, in the exhaust pipe), vacuum leaks (are gaskets OK?), and when those are fine, then given the number of miles, I'd swap out for new oxygen sensors.

Preferably you get the Bosch Planar type sensor. These are like $60 each online. These planar designs are more resistant to contamination than traditional thimbles. I know because I solved P0420 that way.

I can't imagine how many owners, along with Honda, Toyota and others paying for new converters when the problem is with defective oxygen sensors.
 

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mine was the same problem but different code p2423. It have to deal with the cat below threshold bank 1 too. the dealers replaced my catalyst converter 4+ times and all the o2 sensors. But the code keeps coming back on. Since i need the car for classes it took them a year to fix it. guess what the problem is? They trace all the electrical wiring to see if any where loose and they find one near the engine block that was causing the problem. And luckily it was still under warranty so all those cats were free and the o2 sensors. The code came on at 52,000 miles
 

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2GR FTW
2007 Toyota Camry SE
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1,543 Posts
Yeah, typically sounds like the sensor 2 O2 sensors, would be the b1s2 sensors. Bosch universal O2s are around $60 as mentioned to replace.

Sensor 2 is just for reads in cat, only the s1's affect performance and stuff, I'm pretty sure there isn't any harm with malfunctioning s2's, other then emissions tests.
 

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07 Camry LE
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I can't imagine how many owners, along with Honda, Toyota and others paying for new converters when the problem is with defective oxygen sensors.
I would be willing to bet that the numbers are higher than you think. I sell around 100 converters a month out of my store. I would imagine that a lot are sold because pipes rot or flex joints break. However, I get many converters returned to me by customers that couldn't diagnose their way out of a paper bag.
 

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イリジウム
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13,823 Posts
If other parts checked out (engine properly tuned, valve clearances correct, no air/vacuum leaks), then I'd try replacing BOTH upstream and downstream Denso sensors with Bosch planar type whenever available.

http://www.boschautoparts.com/Products/OxygenSensors/PlanarO2

Also check out this article on P-0420 while the tailpipe is "blowing zeros"!!

http://www.motor.com/magazine/pdfs/012009_02.pdf



Yeah, typically sounds like the sensor 2 O2 sensors, would be the b1s2 sensors. Bosch universal O2s are around $60 as mentioned to replace.

Sensor 2 is just for reads in cat, only the s1's affect performance and stuff, I'm pretty sure there isn't any harm with malfunctioning s2's, other then emissions tests.
 

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13 Camry SE, 10 Venz
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110 Posts
There are common Engine Computer issues with Corollas and Siennas that lead to P0420. Check for TSBs for your vehicle.
 
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