Help with Code

[drunkenrich]

Check engine light was on today, had my buddy scan it. Car is a 1996 camry le 4 cyl. Came back "P0420 Catalyst System Efficiency Below Threshold" I'm guessing the cat converter is shot. anyone know what this code means? thanks guys

[haux]

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http://www.toyotanation.com/forum/sh....php?p=2804169

Originally Posted by JohnGD

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.

Originally Posted by JohnGD

1) Replace Downstream 02 sensor
2) Replace Upstream O2 sensor and see if problem goes away

And read the following article before doing #3:

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

3) Replace Catalytic Converter