P02B4 Diagnostic Trouble Code: Cylinder 7 – Injector Restricted

Fault code P02B4 is called “Cylinder 7 – Injector Restricted” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P02B4

The stored code P02B4 means that the Powertrain Control Module (PCM) has detected a possible fuel injector blockage for a specific engine cylinder. In this case, the restriction affected cylinder #7.

P02B4 Diagnostic Trouble Code: Cylinder 7 – Injector Restricted

Automotive injectors require perfectly accurate fuel pressure. To deliver the right amount of fuel in a precisely atomized pattern to the combustion chamber of each cylinder. This circuit requires that each fuel injector be free of leaks and blockages.

The PCM monitors factors such as the degree of fuel correction required as well as data from the oxygen sensor in the exhaust. Additionally, the position of the crankshaft and camshaft are taken into account. This is necessary in order to detect a lean mixture and to determine precisely in which cylinder of the engine the malfunction has occurred.

Data signals from the oxygen sensors alert the PCM to the poor oxygen content in the exhaust gases and which engine block is affected. In turn, the position of the camshaft and crankshaft helps determine which injector has a problem.

Once the PCM determines that there is a lean mixture and detects a damaged fuel injector in cylinder #7. Code P02B4 will be stored and the Malfunction Indicator Light (MIL) may illuminate.

In some vehicles, it may take several failure cycles for the MIL to illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P02B4 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related fault codes may also be present.
  3. Floating revolutions, the vehicle engine may be unstable.
  4. Increased fuel consumption.
  5. Engine stalls or fails to start.
  6. Jerking/missing ignition at idle or under load.
  7. Bad acceleration.

The severity of error P02B4 is above average, caution should be exercised. Since a poor fuel mixture can cause damage to the cylinder head or engine.

Factors that can cause this error code

The error code P02B4 can mean that one or more of the following problems have occurred:

  • Opened or short-circuited injector wires.
  • Clogged fuel injector.
  • Complete failure of injector.
  • Wiring harness is intermittently shorted to components under the hood.
  • Loose or corroded connector.
  • Failed oxygen sensor.
  • Faulty Mass Air Flow (MAF) or Manifold Air Pressure (MAP) sensor.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P02B4

Some suggested steps for troubleshooting and fix the error code P02B4:

  1. Read all stored data and error codes with an OBD-II scan tool.
  2. Clear the error codes from the computer memory.
  3. Test-drive the vehicle to see if error P02B4 appears again.
  4. Visually inspect the fuel injectors and associated wires and connectors for damage.
  5. Check the operation of the fuel injectors.
  6. If necessary, check the operation of the fuel injectors on a special test bench.
  7. Check the oxygen sensor.
  8. Diagnose the Mass Air Flow (MAF) or Manifold Air Pressure (MAP) sensor.
  9. Test the engine control module (ECM).

Diagnose and repair of problems

Starting the diagnosis of P02B4, check the battery voltage (12 V) on the injector connector wire. If there is no voltage, check for continuity to the ground using a test lamp. Connected to the plus side of the battery. If it lights up, there is a short to the ground in the voltage supply circuit.

Correct the short in the voltage supply circuit and restore proper battery voltage. Remember to check the fuse and replace it if necessary.

One injector may short out the battery voltage to all injectors.

If battery voltage is being supplied to the injector wiring harness, the next step is to turn on the light to check that the injector driver is working. Install the injector light in the injector wiring harness instead of the fuel injector. This will flash quickly when the injector driver is operating.

Check the resistance on the fuel injector if you have resistance specifications. If the resistance is above or below the rating, replace the fuel injector. If the injector passes the test, the problem is probably unstable wiring.

Remember that a fuel injector can work fine when cold, but be faulty when hot, or vice versa.

Check the wiring harness

Check the wiring harness for chafing, and the connector for loose contacts or a broken lock. If necessary, repair and check if error P02B4 returns.

Disconnect the PCM connector and connect to the fuel injector driver circuit. Any resistance indicates a problem. Endless resistance indicates a break in the circuit. Locate and repair, then try again.

If you cannot find any problems with the harness, but the fuel injector driver does not work, check the PCM power and ground. If they are OK, the PCM itself may be faulty.

If the electrical part is OK, the injector itself is probably clogged or contaminated. Try cleaning it, the flushing kit is inexpensive and will also help the other injectors work better. If flushing does not solve the problem, the injector must be replaced.

On which vehicles does this problem occur most frequently

Fault code P02B4 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Dodge
  • Ford (Focus, Transit)
  • Land Rover
  • Maybach
  • Mitsubishi
  • Subaru

Fault code P02B4 can sometimes be found with other errors. The most common are the following: P029C, P02A0, P02A4, P02A8, P02AC, P02B0, P02B8, P02BC, P02C0, P02C4, P02C8.

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