P0171 – OBD-II DTC

OBD-II DTC P0171 – Fuel Trim Malfunction (Bank 1)

DTC P0171 meaning

DTC P0171 indicates a fuel trim malfunction on Bank 1 of the engine. This code is triggered when the engine control module (ECM) detects that the air-fuel mixture is too lean, meaning there is not enough fuel being injected into the engine compared to the amount of air. The ECM adjusts the fuel trim to maintain the optimal air-fuel ratio, but if it exceeds a certain threshold, this code will be set.

DTC P0171 symptoms

Common symptoms associated with DTC P0171 include:

• Check Engine Light (CEL) illuminated
• Rough idling or stalling
• Decreased engine performance
• Poor fuel economy
• Engine hesitation during acceleration

DTC P0171 causes

Several factors can lead to the triggering of DTC P0171, including:

• Vacuum leaks in the intake manifold or vacuum hoses
• Faulty mass air flow (MAF) sensor
• Clogged fuel filter or weak fuel pump
• Dirty or failing fuel injectors
• Exhaust leaks before the oxygen sensor
• Faulty oxygen sensor
• Incorrect fuel pressure

DTC P0171 seriousness

DTC P0171 can be serious as it indicates that the engine is running too lean, which can lead to engine damage over time. Prolonged operation under these conditions may result in:

• Increased engine temperatures
• Potential for engine misfires
• Damage to the catalytic converter

It is advisable to address this code promptly to avoid further complications.

How to diagnose DTC P0171

To diagnose DTC P0171, follow these steps:

1. Use an OBD-II scanner to confirm the code and check for any additional codes.
2. Inspect for vacuum leaks in hoses and the intake manifold.
3. Check the MAF sensor for proper operation and cleanliness.
4. Examine the fuel system, including the fuel pump and filter.
5. Inspect the oxygen sensors and their wiring.
6. Perform a visual inspection for any exhaust leaks.

How to fix DTC P0171 step-by-step instructions

To fix DTC P0171, follow these steps:

1. Identify and repair any vacuum leaks.
2. Clean or replace the MAF sensor if it is dirty or faulty.
3. Check and replace the fuel filter if clogged.
4. Test the fuel pump for proper pressure and replace if necessary.
5. Inspect and clean the fuel injectors or replace them if they are faulty.
6. Replace any faulty oxygen sensors.
7. Clear the DTC and perform a test drive to see if the code returns.

How to erase DTC P0171

To erase DTC P0171, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Access the scanner’s menu and select the option to clear or erase codes.
4. Confirm the action and wait for the scanner to indicate that the codes have been cleared.
5. Disconnect the scanner and start the engine to ensure the code does not return.

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