Vauxhall fault code P0171 – System too lean (bank 1)

Delphi Delco MT35E

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What does this fault code mean?

If during the read out of the fault codes on a Vauxhall the OBD-II code P0171 appears, then there is not enough fuel or too much air in the cylinders. The engine runs too lean.

In which models does this code appear?

Primarily all models that are equipped with the Z16XER/P or Z18XER motor

Symptoms for fault code P0171 (Vauxhall)

As soon as the fuel-air ratio is not as required, the engine will not perform effectively This can cause a loss in engine power. The P0171 fault can also cause an irregular idle rpm and in certain cases the car will not start. If this fault is not repaired damage may be caused to the catalytic converter. This is the reason that in most cases the engine management light on the instrument cluster will illuminate as soon as P0171 fault exists.

Causes of the P0171 code

Fault code P0171 can be caused for example by the fuel filter, fuel pressure valve or fuel pump. But a vacuum leak or defective injector can trigger the P0171 fault code as well. It is often thought that the Delphi Delco MT35E ECU (the ECU for the Z16XER/P and the Z18XER engines) is the cause of the problems, but this is not always the case.

Our advice on a P0171 fault code

Good diagnosis with this fault is very important. Work methodically and check all parts that are concerned with the fuel supply, from fuel pump to fuel injectors. Do the same for the whole exhaust system.

Pro tip: The swirl flap in the inlet manifold might cause problems, Dirt and debris can permanently shut the valve. If all other options are exhausted it is always possible to contact us for further assistance.