PowertrainP0040
CautionSeverity: Caution - get it checked when you can
O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1
Key terms: Oxygen sensor: measures oxygen in the exhaust gas · Mass air flow sensor: measures the air going into the engine · Bank 1: the side of the engine containing cylinder 1 · Bank 2: the side of the engine containing cylinder 2 · SAE J2012: the standard generic code list · Powertrain: engine, transmission and emissions
1What it means in plain English
This code is in the fuel and air metering range, which includes fuel-pressure and camshaft-timing faults.
2Common causes
- Dirty or faulty mass air flow sensor
- Vacuum or intake air leak
- Weak fuel pump or clogged fuel filter
- Faulty fuel injector
- Faulty oxygen sensor
- Wiring or connector fault
3Can I drive?
Have it diagnosed promptly. Some codes in this range affect fuel pressure or camshaft timing; if the engine loses power, runs badly, or stalls, stop safely and get professional help.
This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.
4Brand data 31
| Brand | Code | Description | System |
|---|---|---|---|
| Ashok Leyland CV | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| BAIC Motor | P0040 | Drive motor IGBT fault Brand | Powertrain |
| Mercedes-Benz | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| BMW | P0040 | mixed-up oxygen sensors Brand | Powertrain |
| BYD | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Chery | P0040 | SAE: oxygen sensor Signals Swapped: B1-S1 B2-S1 Brand | Powertrain |
| Chrysler | P0040 | 1/1 and 2/1 oxygen sensor harness connectors reversed Brand | Powertrain |
| Daewoo | P0040 | Automatic-Transmission Input Speed Circuit No Signal Brand | Powertrain |
| DFFS | P0040 | Sequential solenoid coil 1 output fault Brand | Powertrain |
| DFFX | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| DFXK | P0040 | SAE: Oxygen Sensor Signals Swapped: B1-S1 B2-S1 Brand | Powertrain |
| EOBD | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Geely | P0040 | SAE: Oxygen Sensor Signals Swapped: B1-S1 B2-S1 Brand | Powertrain |
| GM | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Great Wall | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Hafei | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Holden | P0040 | HO2S Signals Swapped Banks 1 and 2 Sensor 1 Brand | Powertrain |
| Honda | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Hyundai | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Isuzu | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Land Rover | P0040 | Heated oxygen sensor 1-1 Signal swapped to 2-1 Brand | Powertrain |
| Maserati | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Opel | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Peugeot | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Porsche | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1 / Bank 2 Sensor 1 SAE | Powertrain |
| Saab | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| MG (SAIC) | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 Brand | Powertrain |
| Tata | P0040 | O2 Sensor Signals Swapped Bank 1 Sensor 1/ Bank 2 Sensor 1 Brand | Powertrain |
| Toyota | P0040 | Sequential solenoid coil 1 output fault Brand | Powertrain |
| Volvo | P0040 | Upstream HO2S Sensors Swapped Brand | Powertrain |
| Volkswagen | P0040 | Oxygen (Lambda) sensor signals swapped: B1-S1 / B2-S1; Open circuit Brand | Powertrain |
Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.
5Extended variant codes 2
These 7-character codes are manufacturer-specific variants of P0040 and may be reported by some scan tools.
| Brand | Code | Description | System |
|---|---|---|---|
| Mercedes-Benz | P004000 | Oxygen sensors 1 (cylinder banks 1 and 2) have been swapped. Brand | Powertrain |
| Porsche | P004000 | No description available | Powertrain |
6Related codes
Browse Pxxx codes or P004xx codes.