What does code P1156 mean?

Q: What does code P1156 mean?

HO2S Rich Average Bank 2 Sensor 1. P1156 on a GM vehicle means the powertrain control module has detected a rich average fuel trim condition on bank 2, sensor 1, which is the upstream oxygen sensor on the bank of cylinders that does not contain cylinder 1. The computer is reporting that the exhaust stream on that bank is consistently richer than the fuel control system can correct, based on the average of the sensor's voltage signal over a calibrated time window.

DTC codes / GM codes / P1156

P1156 · GMHO2S Rich Average Bank 2 Sensor 1

P1156 on a GM vehicle means the powertrain control module has detected a rich average fuel trim condition on bank 2, sensor 1, which is the upstream oxygen sensor on the bank of cylinders that does not contain cylinder 1. The computer is reporting that the exhaust stream on that bank is consistently richer than the fuel control system can correct, based on the average of the sensor's voltage signal over a calibrated time window.

SystemPowertrain

Code typeGM specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.