# Catalytic converters and oxygen sensors **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [October 18, 2011, 2:09am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739 "2011-10-18T02:09:38Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![williamclang](https://avatars.discourse-cdn.com/v4/letter/w/6f9a4e/32.png) [@williamclang](https://community.cartalk.com/u/williamclang)\ **Post date:** [October 18, 2011, 2:09am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/1 "2011-10-18T02:09:38Z")
My son-in-law has a 2006 Honda Accord with over 160,000 miles on it. About 8 months ago, the check engine light came on. The code said the down stream oxygen sensor was bad. He took it to a Honda dealer and they replaced the sensor and now the check engine light is back on with the same code. Can the catalytic converter have gone bad and can it have made the oxygen sensor go bad too? ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [October 18, 2011, 3:19am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/2 "2011-10-18T03:19:17Z")
There aren’t any codes that tell you that oxygen sensors are bad. Provide some details. What is the exact code? The format is “P1234.” These codes are just a starting point for diagnostics. What was done the last time in terms of actual diagnostics? ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [October 18, 2011, 4:14am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/3 "2011-10-18T04:14:49Z")
Diagnosing converter and O2 problems can be a real head scratcher at times and they’re often misdiagnosed. Did your SIL diagnose the problem and then ask the dealer to change the sensor? If this is the case the dealer made a mistake by replacing a part based on someone else’s recommendation. It should not be inferred that the word mistake means the dealer should be liable in any way for this problem. ---
**Author:** ![Caddyman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/caddyman/32/23_2.png) [@Caddyman](https://community.cartalk.com/u/Caddyman)\ **Post date:** [October 18, 2011, 4:17am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/4 "2011-10-18T04:17:00Z")
Cig is correct…Post the code… ---
**Author:** ![Manolito](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/manolito/32/3070_2.png) [@Manolito](https://community.cartalk.com/u/Manolito)\ **Post date:** [October 18, 2011, 4:26am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/5 "2011-10-18T04:26:07Z")
As part of the diagnostics, check carefully for an exhaust leak between the first oxygen sensor and the cat. ---
**Author:** ![Mechaniker](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@Mechaniker](https://community.cartalk.com/u/Mechaniker)\ **Post date:** [October 18, 2011, 7:31am UTC](https://community.cartalk.com/t/catalytic-converters-and-oxygen-sensors/68739/6 "2011-10-18T07:31:39Z")
There is a Honda TSB on two error codes (P1172 and P2A00) for the pre-cat O2 sensor. There may be a similar TSB on DTCs for the post-cat O2 sensor, but you would have to look them up yourself, or at least insist that the dealer does. The dealer typically _will not_ look up this TSB unless the owner tells him about it before hand. The dealer will have it in his electronic data base, however. The TSB calls for a reflash of the CPU, which essentially widens the tolerance limits on the voltage output of the O2 sensor before a MIL is set. The cost of the reflash in my neck of the woods is $145. ![](http://static.cl1.vanilladev.com/cartalk.vanillaforums.com/uploads/FileUpload/42/24f33894fd15b884a36528bcbd8492.pdf)