Hi all. '09 Pontiac Vibe GT (2az fe oil burner) 175k. Getting an intermittent p0420 code. Scanner says catalyst bank sensor 1 temperature ~470 celsius, sensor 2 ~300 celsius. All the catalyst and O2 sensors tests say "pass" every time. Sometimes I'll have a p0420 (1/2) code that won't trigger the CEL, but then I'll get two p0420 (1/2 and 2/2) codes that trigger the CEL. After clearing, the codes come back anywhere from 30 to 300 miles. Can anyone derive any useful information from this? Thanks in advance!
Anyone an expert on catalytic converters?
- Thread starter Jonas
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The cat is on its way out. Burning oil can damage it over time.
The code that doesn't trigger the CEL is a pending code.
Some time before inspection is due, get a California-legal cat and the oxygen sensors. Maybe also switch to a thicker oil or HM
The code that doesn't trigger the CEL is a pending code.
Some time before inspection is due, get a California-legal cat and the oxygen sensors. Maybe also switch to a thicker oil or HM
Most likely the rear sensor is reading lean at times. When not coasting the rear sensor should give a rich reading at all times as the catalyst is supposed to consume all oxygen left in the exhaust gas. This can be caused by a lazy front sensor (slow to switch from lean to rich reading) or because the cat is done.
on the low side to me...
should be 4 wires going to each sensor, 2 of those are an electric heater.
Look at the cycling speed. 2 full cycles per second is what you want to see. Lean -rich - lean - rich...
Look at the cycling speed. 2 full cycles per second is what you want to see. Lean -rich - lean - rich...
Temp on the rear O2 should be higher than the front, check the cat temp in the front of it and the rear if its not higher in the rear by about 100f there is no action taking place in the cat. Cat temps look okay so I would guess a bad cat if an infrared thermometer matches the temps you are getting.
I suspect it may be starting to plug up, You could try removing it and hollowing it out by breaking the inside core up with a long chisel and hammer.
You will need to use a extension on the rear o2 to put the CEL out.
This is for testing only how long you test it is your business.
You will need to use a extension on the rear o2 to put the CEL out.
This is for testing only how long you test it is your business.
Any opinion on cleaners like oxicat?
I never tried any so I really have no opinion.
how do they estimate the sensor temp? seems it's prone to misreading if they go by reaction speed or internal resistance.
I have no idea. My scanner just says Catalyst temperature (on average) 470 Celsius sensor 1, 300 Celsius sensor 2. Both temps start falling at idle at about the same rate.
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