obd codes came up on my truck po-137. 02 sensor circuit ,low voltage bank one-sensor-2, im pretty sure I need too replace that sensor, what I was wondering is I got 2 more codes that came with. po-420 and po-430, saying catalyst system efficiency below threshold bank-1 which is the 420 code and the same reading for 430-bank -2 anybody got any info on what I need to do too clear them codes? thanks
Chevrolet Q&AAsk Your Question
1999 Chevrolet Silverado 1500 Question: how to clear 3 codes on 99 chevy Silverado ls 5.3?
Answer #1ChevyASE September 06, 2013, 02:47Journeyman
I know what to do, but you won't like it. You need the cats replaced. Common problem. Unfortunately, they are sold as the whole Y-Pipe assy. The cats usually die due to contamination. Have you had any repairs done recently for oil or coolant being burned (i.e. Head gasket, intake leak, or valves)? Also, how does the engine run? Any misfires current or that were fixed recently? For the HO2s code P0137, check for exhaust leaks prior to that sensor. Make sure the sensor wires are not broken cut or melted. Pull your spark plugs and see if any are fouled. If you have access to a scan tool, do an injector balance test and look for lean conditions on the left bank. If these things check out normal (which they most likely will) replace the sensor when doing the cats.