How to Replace Fuel Injectors Using Autel Scanner

The fuel injector is like the engine's "precision sprayer," responsible for atomizing gasoline into a very fine mist and spraying it into the engine at the right time for efficient mixing with air and complete combustion. This ensures the car has ample power while also achieving fuel efficiency and environmental protection.

Typically, a fuel injector only needs to be replaced when it's severely clogged, mechanically damaged, or has an electrical fault that causes serious engine operating problems.

The Autel Scanner is crucial during this process, as it not only diagnoses the problem to identify the faulty injector, but also programs its unique identification code (ID) into the engine computer after the new injector is replaced, ensuring the system can correctly recognize and control it.

Replace Fuel Injector

Signs You Need to Replace Fuel Injectors

1. Engine Shake and Idle Unstable
   • Description: When stopping or waiting at a red light, the steering wheel and vehicle body may feel noticeable shake, and the tachometer needle may fluctuate.
   • Cause: One or more injectors are clogged or damaged, resulting in abnormal fuel supply to the corresponding cylinders and uneven work.
2. Weak Acceleration and Reduced Power
   • Description: When you step on the accelerator, the car feels "sluggish," accelerating slowly and making overtaking difficult, as if its power is blocked.
   • Cause: Clogged fuel injectors result in insufficient fuel injection or poor atomization, significantly reducing combustion efficiency.
3. Significantly Increased Fuel Consumption
   • Description: Abnormally high fuel consumption with no significant changes in driving habits or road conditions.
   • Cause: The fuel injectors are not properly closed, causing dripping or continuous leakage, allowing fuel to enter the cylinders when it is not needed, resulting in wasted fuel.
4. Difficult Starting or Stalling
   • Description: The engine requires multiple ignition cycles to start, or it automatically shuts down while waiting at a red light after driving.
   • Cause: Severe fuel injector blockage results in a lean fuel mixture during startup, preventing ignition.
   

   Difficult starting may be caused by a faulty fuel injector.

5. Abnormal Exhaust Emissions
   • Description: Distinct black smoke and a pungent gasoline odor are emitted from the exhaust pipe.
   • Cause: Fuel injector leakage or excessive fuel injection results in an overly rich fuel mixture, preventing complete fuel combustion.
6. MIL (Middle Indicator Light) Illuminated
   • Description: The engine-shaped warning light (MIL) on the instrument panel is illuminated or flashing.
   • Cause: The ECU detects an abnormality in the injector circuit or performance (for example, a general fault code such as P0200 - Injector Circuit Fault, or a cylinder-specific fault code such as P0201 or P0202).
7. Severe Combustion Chamber Carbon Deposits
   • Description: During an endoscopic inspection or disassembly, abnormally severe carbon deposits were found on the piston crown or spark plug of a cylinder.
   • Cause: The injector in that cylinder has poor atomization, spraying like a "water gun," preventing the fuel from evaporating and burning, resulting in carbon deposits.

Carbon deposits in the combustion chamber may be caused by damaged fuel injectors.

Tools and Preparations

Before replacing a fuel injector, thorough preparation is crucial to ensuring a smooth and safe repair.

Required tools

• New fuel injector (original or equivalent): It is recommended to use the same model as the original vehicle to ensure compatibility in spray volume, atomization angle, and interface.
• Basic hand tools: This includes a socket wrench, ratchet wrench, screwdriver, etc. for removing the intake manifold, fuel rail, and retaining clips.
• Autel diagnostic scanner (such as the MaxiSys Ultra, or MS908S Pro II): Used to read injector data and fault codes before replacement and perform injector coding and system self-learning after replacement.
• Safety equipment: Protective gloves and goggles to prevent injury from fuel splashes or metal debris.

Preparation:

1. Park the vehicle on a flat, secure surface. Apply the parking brake and turn off the ignition.
2. Disconnect the negative battery terminal to prevent accidental short circuits or triggering electronic systems.
3. Release fuel system pressure: This can be done by removing the fuel pump fuse or using a diagnostic tool to perform the "Fuel System Depressurization" function to prevent fuel from spraying when removing the injectors.
4. Open the engine compartment and use an Autel scanner or the repair manual to confirm the exact location and number of the injectors.
5. Inspect the wiring, vacuum hoses, and fuel rail connections surrounding the injectors to ensure no damage is caused during removal.

Once these preparations are complete, you can safely proceed with injector removal and replacement.

Inspection and preparation before replacing the fuel injector

Step-by-Step Guide to Replace Fuel Injectors

Step 1: Diagnosis and Recording

Connect your Autel diagnostic tool to the vehicle's OBDII port and perform a full system scan to read and confirm injector-related DTCs (DTCs), such as the P0200 series. This will help you pinpoint the faulty cylinder.

Before removing any components, be sure to access the scanner's "Injector Coding" or related menu and record the identification codes of all old injectors. This step is crucial for future reference.

Step 2: Safe Disassembly

Before beginning any mechanical work, disconnect the negative battery terminal for safety. Next, refer to the repair manual and carefully disconnect the fuel line quick connector and injector wiring harness connector.

Remove the fuel rail mounting bolts. Carefully lift and remove the entire fuel rail assembly, including the injectors. Be gentle when removing the old injectors to avoid damaging their mounting sockets.

Steps for programming fuel injectors using Autel scanner

Step 3: Careful Installation

When installing new injectors, all seals and O-rings must be replaced with new ones. Before installation, lightly lubricate the new seal with clean engine oil to help prevent twisting or damage during installation.

Ensure the new injector is fully and evenly seated on the fuel rail. Then, return the entire assembly to the engine and reconnect the fuel lines and electrical connectors.

Step 4: Programming and Verification

Reconnect the battery. Turn the ignition switch to the "ON" position (but do not start the engine). The fuel pump will operate to build system oil pressure. Using your Autel scanner, access the "Injector Coding" or "Programming" function.

First, clear the old injector data, then accurately enter the unique identification number printed on the new injector. After programming is complete, start the engine.

Using the scanner's live data streaming function, closely monitor injector balancing tests, misfire data, and short- and long-term fuel trim values to ensure all parameters are normal and the engine is running smoothly with no signs of leaks.

Please refer to the following coding process for BMW N54 after replacing the fuel injector:

Conclusion

Using an Autel scanner makes replacing fuel injectors more efficient and accurate. It helps users quickly read fault codes, complete injector coding, and verify the replaced injector's working condition.

With the correct coding, the engine control unit can identify the parameters of the new injector, thereby improving combustion efficiency, reducing fuel consumption, and restoring optimal performance.

Whether you're a professional technician or a DIY car owner, Autel scanners (such as the MS919, Ultra S2, and MS909) are reliable tools that make injector replacement and matching easy.