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AutoCodes – Generic – P311B

P311B Code - Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical

Quick Answer

The solenoid-controlled injection valve discharges a high-pressure spray into the combustion chamber. Common causes include Faulty Fuel Injector 3, Fuel Injector 3 harness is open or shorted, Fuel Injector 3 circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P311B indicates Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical.
Common causes
Common causes include Faulty Fuel Injector 3, Fuel Injector 3 harness is open or shorted, Fuel Injector 3 circuit poor electrical connection.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code Popularity 605
How popular is this code, among other codes? Low
What is this?
Table of contents Created and updated by William Orellana on Jul 16, 2020
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Code P311B Description

The solenoid-controlled injection valve discharges a high-pressure spray into the combustion chamber. The solenoid-controlled injection valve is a retracting-plunger valve characterized by a high level of flexibility in its spray-propagation pattern (angle and shape). The discharge orifices form the high-precision injection pattern. This provides even and consistent propagation. The retracting-plunger solenoid-controlled injection valve continues to maintain stable propagation properties, even at the temperatures and pressure levels encountered within the combustion chamber. Fuel is injected into the combustion chambers under high pressure (between 50 and 200 bar) during the intake and compression strokes. During the warm-up phase yet another, a minute quantity of fuel is injected to assist the catalytic converter to reach its effective operating temperature more quickly (catalytic converter heating). During cold starting, the fuel is sprayed during the compression stroke in multiple pulses. This strategy provides reliable cold-starts along with substantive improvements in the areas of pollutant emissions and fuel consumption.
The Digital Motor Electronics (DME) diagnosis monitors the activation of the high voltage side of the fuel injector. The Diagnostic Trouble Code (DTC) is detected when there is a short circuit between the high-voltage side and the low-voltage side.
OBDII Code P311B - Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical - AutoCodes.com
P311B Code - Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical
What does this mean?

What are the Possible Causes of the DTC P311B?

  • Faulty Fuel Injector 3
  • Fuel Injector 3 harness is open or shorted
  • Fuel Injector 3 circuit poor electrical connection
  • Faulty Digital Motor Electronics (DME)

How to Fix the DTC P311B?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P311B code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P311B code?

Need more information on how to fix the P311B code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P311B code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

  • P311B BMW — Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical
  • P311B MINI — Cylinder 3 High Pressure Fuel Injector Low Side/High Side Electrical
About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P311B Code

1. What does the OBDII code P311B mean?

P311B indicates an electrical issue in the high or low side circuit of the high-pressure fuel injector for cylinder 3.

2. What are the common symptoms of a P311B code?

Symptoms may include rough idling, engine misfires, reduced fuel efficiency, loss of power, or the Check Engine Light turning on.

3. What causes the P311B code to appear?

Possible causes include a faulty cylinder 3 fuel injector, damaged wiring or connectors, a failing fuel injector driver circuit, or a malfunctioning engine control module (ECM).

4. Can I drive with a P311B code?

Driving with this code may result in reduced engine performance, and prolonged operation could cause further damage. It’s best to address it promptly.

5. How do I diagnose the P311B code?

Diagnosis involves inspecting the wiring and connectors for cylinder 3, testing the fuel injector for proper operation, and checking the ECM for faults.

6. How is a P311B code fixed?

Repairs may involve replacing a faulty fuel injector, repairing damaged wiring or connectors, or reprogramming or replacing the ECM if necessary.

7. Can a dirty fuel injector cause a P311B code?

While dirt or debris can affect fuel injector performance, this code specifically refers to an electrical issue, not a clog or blockage.

8. What tools are needed to troubleshoot a P311B code?

You’ll need an OBDII scanner, a multimeter for testing electrical circuits, and possibly specialized tools to remove and inspect the fuel injector.

9. Will clearing the code fix the issue permanently?

Clearing the code may turn off the Check Engine Light temporarily, but the underlying issue must be fixed to prevent the code from returning.

10. Can a failing ECM cause the P311B code?

Yes, a malfunctioning ECM can fail to properly control the injector’s electrical circuit, triggering this code.

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