I was logging some PIDs today and noticed that at a stop the B2S2 sensor voltage drops to below .20 while the other hangs out around .70. While driving they basically stay in sync.
Is that indicative of a bad cat?
Help me understand rear O2 sensor voltage (2012 f150)
- Thread starter DSG2003Mach1
- Start date
I was logging some PIDs today and noticed that at a stop the B2S2 sensor voltage drops to below .20 while the other hangs out around .70. While driving they basically stay in sync.
Is that indicative of a bad cat?
yes
the rear o2s should switch slow and take a while to go lean
the rear o2s should switch slow and take a while to go lean
Just to be sure here I’m understanding your response - this would indicate a bad cat before I go buy a new mid pipe ? Tired of dealing with this random ass light
Correct. Since you did replace the sensor, and still getting the same issue. B1S2 is a good reference as to how it should react. If rear oxygen sensor is switching from rich to lean at a somewhat fast frequency. Most likely it is because cat has stopped working properly.
here goes another $700-$800 into this ****ing truck lol
...still cheaper than a new one
Yeah it's not that complicated when it comes to rear O2s. They are basically just cat monitors. Here is a simplified flow chart. You will definitely want to replace OE spec cat.
1. Monitor the rear sensors while you are driving.
2. If the rear sensors are switching rapidly, this would suggest the catalytic converters are no longer functioning.
3. Before replacing them, ensure there are no issues with coolant or oil getting into the exhaust, no misfires, and no rich or leann conditions.
4. Note: Catalytic converters that do not meet the factory specifications will also set these codes.
1. Monitor the rear sensors while you are driving.
2. If the rear sensors are switching rapidly, this would suggest the catalytic converters are no longer functioning.
3. Before replacing them, ensure there are no issues with coolant or oil getting into the exhaust, no misfires, and no rich or leann conditions.
4. Note: Catalytic converters that do not meet the factory specifications will also set these codes.
just as another way to diagnose the cats - if you have Forscan it will give test results from Mode 6 data. It shows the Oxygen storage capacity is out of spec @ .805 and upper limit is .785.
The other cat is .660
Mode 6 shows no misfires. I don't have any oil or coolant consumption, I believe the cat was damaged back in the day from 2 pretty bad "ecoboost shutter" moments where it blew shit out of the intercooler into the motor on the highway (since added a drain hole).
The other cat is .660
Mode 6 shows no misfires. I don't have any oil or coolant consumption, I believe the cat was damaged back in the day from 2 pretty bad "ecoboost shutter" moments where it blew shit out of the intercooler into the motor on the highway (since added a drain hole).
most of the ecoboost shuttering issues i've ran across is from the wastegate
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