202 is a post cat bank 1 fault code.
With a hot engine, monitor the sensors voltage.
Reading the Post-Cat O2 sensor voltage:
- Cat's in good condition have Post-Cat O2 voltages above 0.5V. When at steady highway cruise, there may be the odd momentary dips.
- If O2 sensors are switching between 0.1 and 0.8V, this shows that the Cat’s are not able to treat the exhaust and indicates struggling Cat's. They are following the pre-cat O2 sensors. This is the same for either narrow band or wide band Pre-Cat O2 sensors. Expect to start seeing P0420 and P0430 Cat efficiency below threshold codes.
- If O2 sensors are flat lined somewhere below 0.5V, you have one of these problems:
- Faulty post-cat sensors
- Blocked Cats. Check fuel trims, they are likely double-digit rich at cruise RPM’s. Do a before the Cat’s exhaust pressure test.
- Fuel mixture problems that are so lean that it is being reflected in the post-cat O2 sensor signals
Are you sure this 202 code is the post cat sensor? The German text refers to control limit which is more applicable to the pre cat sensor.
The answer I gave earlier only applies to the post cat sensor, the pre-cat sensor is the primary fuel control sensor and if that’s faulty, then emissions will be shot and it’ll probably run rough too.
Here’s some better advice: ditch INPA, Creator and all other ancient junk that doesn’t display DTCs in the industry standard format - powertrain codes should be displayed Pxxxx.
Oxygen sensor codes, typically P0130, P0135, etc. you’ll stand a much better chance of successful diagnosis with good data.
This stuff has been mandated for over 20 years. Half decent readers are given away free as phone apps,
rant over.
