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Re: P0420 - Been there and battled this one.... Posted by MI-Roger [Email]  (#882) [Profile/Gallery]
(more from MI-Roger) on Mon, 29 Oct 2012 15:38:41
In Reply to: P0420 maybe oil blowby?, Udailey, Mon, 29 Oct 2012 14:54:19 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Catalytic Converter or O2 sensor(s) or wiring.
This code is produced when the reading from the rear O2 sensor (after the Catalytic converter) does not vary sufficiently from that produced by the front O2 sensor.
Meaning either:
- Your catalytic converter is toast and not doing its job
- The rear O2 sensor has failed
- The front O2 sensor has failed
- Wiring issues are preventing the ECU for receiving the correct signals from the O2 sensor(s)
- The rear O2 sensor is not positioned properly within the pipe for an accurate reading due to your modified exhaust
This code is commonly seen on cars/trucks with modified Catalytic converters/exhaust systems and usually occurs during steady state easy driving, sometimes more frequently in cold weather.
Michigan does not have mandatory emissions testing so I installed an adapter on the rear O2 sensor to extract it partially from the exhaust gas stream which then caused the code to disappear on my 11 year old 2000lpt with a 3-inch Down Pipe and Saab-Remus exhaust. This treats the symptom rather than the cause and is possibly (probably?) illegal.
A legal option would be to install a large capacity truck converter behind the existing one and move the rear O2 sensor to a new bung behind this added converter. Assuming that you don't live in California where any alteration/substitution of the factory converter is illegal.
->Posting last edited on Mon, 29 Oct 2012 15:42:09.
_______________________________________ Saabs owned: 2008 9-5 Aero Sedan, sold at 227K miles 2006 9-3SC 2.0T - Wife's daily driver 2000 Viggen Convertible - Sold May, 2022 1964 Quantum IV Formula Car - Retirement project 2000 9-5lpt Sedan, sold at 318K miles
, Mon, 29 Oct 2012 15:38:41 <-- Viewing This Message
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