P0040
O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1
1999-2000 BMW 323i E46 2.5L I6 🇬🇧
Moderate SeverityPowertrain
Description
The PCM has determined that the upstream O2 sensor signals for Bank 1 and Bank 2 are swapped, likely due to incorrect wiring after sensor replacement.
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough running
- Failed emissions
Common Causes
- O2 sensor connectors swapped after service
- Wiring crossed between banks
- Incorrect sensor installation
Diagnostic Steps
- Verify which O2 sensor is connected to which bank
- Trace wiring from each sensor to PCM connector
- Check for crossed connectors
Repair Notes
Swap the sensor connectors to the correct banks.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P0040 on Other Vehicles
Common Questions
What does code P0040 mean on a 1999-2000 BMW 323i E46?
P0040 stands for "O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1". The PCM has determined that the upstream O2 sensor signals for Bank 1 and Bank 2 are swapped, likely due to incorrect wiring after sensor replacement.
What are the symptoms of P0040 on a BMW 323i E46?
Common symptoms of P0040 include: Check Engine Light, Poor fuel economy, Rough running, Failed emissions.
What causes P0040 on a 1999-2000 BMW 323i E46?
Common causes of P0040 include: O2 sensor connectors swapped after service, Wiring crossed between banks, Incorrect sensor installation.