P0040: The lambda sensor signals of the two banks are swapped
The lambda sensor signals of the two banks are swapped, almost always because the connectors were swapped after a repair.
| Code | P0040 |
|---|---|
| System | Engine and transmission |
| Group | P00xx, Air, fuel and emissions |
| Type | Generic: it means the same on every make |
How to read and clear P0040 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0040 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P003C Intake camshaft profile control A on bank 1 performs poorly or remains off
- P003D Intake camshaft profile control A on bank 1 remains switched on
- P003E Intake camshaft profile control A on bank 2 performs poorly or remains off
- P003F The variable profile actuator of camshaft A on the second bank is stuck on
- P0041 The signals from lambda sensor 2 on bank 1 and lambda sensor 2 on bank 2 are
- P0042 The lambda sensor heater control (bank 1, sensor 3) has an electrical fault
- P0043 Low signal in the heater of the third lambda sensor
- P0044 The lambda sensor heater control (bank 1
- P0010 Camshaft A actuator control: open circuit (bank 1)
- P0011 Camshaft A timing over-advanced (bank 1)
- P0012 Camshaft A timing over-retarded (bank 1)
- P0013 Camshaft B actuator control: open circuit (bank 1)
What does code P0040 mean?
The lambda sensor signals of the two banks are swapped, almost always because the connectors were swapped after a repair.
How do you clear P0040?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0040 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
