What the P0170 code means?
The P0170 code means that the powertrain control module is detecting a fuel trim that is outside the range of specification set by the vehicle's manufacturer. This can mean a negative fuel trim or a positive fuel trim has been detected. The powertrain control module receives a signal from the oxygen sensors and will adjust the amount of fuel the engine receives based on the readings provided by the oxygen sensors. This action carried out by the powertrain control module is called a fuel trim.
What are the causes of the P0170 code?
1. Intake Manifold vacuum leaks
2. Defective Mass Air Flow Sensor
3. Defective Mass Air Flow Sensor wiring or connections.
What are the symptoms of the P0170 code?
Symptoms for Error Code P0170 may vary depending on the make of the vehicle. Also, other conditions
present can also affect the symptoms. Obviously, it activates the Check Engine light. Some of the most
common symptoms however, include:
1. Loss of power
2. Stumbling from the engine, hesitation on acceleration, start and stall
3. Increased fuel consumption
4. Black smoke coming out of the tailpipe
5. Misfire at idle or under load.
Common mistakes when diagnosing the P0170 code:
The most common cause of this code occurs primarily in European vehicles such as Mercedes-Benz,
Volkswagen, BMW, and Audi. It can be traced to the mass air flow sensor. Either the mass air flow sensor
connector becomes contaminated with engine oil, the sensor hot wire becomes fouled with oil or other
debris, or the air inlet pipe is cracked or broken allowing unmetered air to enter the engine. Aftermarket
mass air flow sensors have also proven to be problematic on this type of vehicle. Faulty oxygen sensors are also fairly common in European models, due to oil fouling in the exhaust system. Other possible causes include an excessively rich fuel condition caused by a faulty fuel pressure regulator, faulty manifold air pressure sensor, or a faulty PCM. This code may also be caused by a lean fuel condition caused from a faulty fuel pump, bad fuel pressure regulator, clogged fuel filter, or engine vacuum leak. Keep in mind that PCM failure is rare.
What repairs can fix the P0170 code?
1. Correcting any condition that causes the engine to run rich
2. Correcting any condition that causes the engine to run lean
3. Replacing the powertrain control module.