P237B code meaning
O2 Sensor Exhaust Sample Error (Bank 2 Sensor 2)
Powertrain system Generic code P23xx codes Check engine light
What P237B means
P237B is the bank 2 version of the sample check on the post-catalyst oxygen sensor and therefore only appears on engines with two exhaust banks, mostly V6 and V8 units with a separate downstream sensor on each side. The ECM decides that what the sensor reports cannot be genuine exhaust from that bank, for example because a leak at the second-bank pipe lets air in or the probe is mounted badly. No manufacturer documents P237B publicly; a published example of the method exists only for the front sensor, Volkswagen's P2414 on the 2014 Golf. CARB demands monitoring of rear sensors because the catalyst check relies on them. Related codes are P237A for bank 1 and P2415 for the bank 2 front sensor; code lists use this title again for P23A1. Inspecting the bank 2 exhaust for leaks comes first.
P237B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P237B
- Check engine light on
- Bank 2 catalyst monitor incomplete or failing
- Engine runs as usual
Common causes of P237B
- Most likelyAir leak in the bank 2 exhaust between catalyst and rear sensor
- PossibleBank 2 rear sensor damaged, poisoned or not seated correctly
- Less likelyRear sensors of bank 1 and bank 2 swapped at the connectors after a repair
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor b2s2Exhaust after catalyst b2
What each part of P237B means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 3 | Area: ignition system or misfire. |
| 7B | The exact fault in that area. |
What to do next
- Note P237B and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P237B
What does P237B mean?
P237B means "O2 Sensor Exhaust Sample Error (Bank 2 Sensor 2)". P237B is the bank 2 version of the sample check on the post-catalyst oxygen sensor and therefore only appears on engines with two exhaust banks, mostly V6 and V8 units with a separate downstream sensor on each side. It is a generic code, so it means the same on every make.
Is it safe to drive with P237B?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P237B fail an emissions test?
Yes, it can. P237B is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P237B to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P237B clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.