P0191 Mercedes-Benz Code - Fuel Rail Pressure Sensor Circuit Range/Performance
Quick Answer
The Fuel Rail Pressure (FRP) sensor is a diaphragm strain gauge device in which resistance changes with pressure. Common causes include High fuel pressure, Low fuel pressure, Damaged FRP sensor. 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
- P0191 Mercedes-Benz indicates Fuel Rail Pressure Sensor Circuit Range/Performance.
- Common causes
- Common causes include High fuel pressure, Low fuel pressure, Damaged FRP sensor.
- 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.
Code P0191 Mercedes-Benz Description
Strain gauge type sensors are consider passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow.
Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each combustion cylinder.
What are the Possible Causes of the DTC P0191 Mercedes-Benz?
- High fuel pressure
- Low fuel pressure
- Damaged FRP sensor
- Excessive resistance in the circuit
- Low or no fuel
- Wiring harness connector of the fuel pressure sensor
- Fuel Rail Pressure Sensor
- Vacuum leaks
- Fuel
How to Fix the DTC P0191 Mercedes-Benz?
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 P0191 Mercedes-Benz 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 P0191 Mercedes-Benz code?
Need more information on how to fix the P0191 Mercedes-Benz code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0191 Mercedes-Benz code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P0191 Mercedes-Benz Code
1. What are the common symptoms of OBDII code P0191 in a Mercedes-Benz?
- Common symptoms include rough idle, poor engine performance, difficulty starting, and possibly a decrease in fuel efficiency.
2. What causes the OBDII code P0191 in a Mercedes-Benz?
- The code is typically triggered by issues with the fuel rail pressure sensor circuit, such as a faulty sensor, wiring problems, or a malfunctioning fuel pump.
3. How can I diagnose the OBDII code P0191 in my Mercedes-Benz?
- Diagnosing the code involves using a scan tool to read the code, checking the fuel rail pressure sensor and related wiring for damage, and verifying the fuel pressure readings.
4. Can a faulty fuel rail pressure sensor be repaired, or does it need to be replaced?
- In most cases, a faulty fuel rail pressure sensor will need to be replaced to resolve the P0191 code and related issues.
5. Are there any DIY repair tips for addressing the OBDII code P0191 in a Mercedes-Benz?
- DIY repair tips include checking for loose or damaged wiring connections, as well as ensuring proper fuel pressure and fuel system functionality.
6. How serious is the OBDII code P0191 in a Mercedes-Benz?
- The code should be addressed promptly to prevent potential engine damage and ensure optimal performance and fuel efficiency.
7. Can driving with the OBDII code P0191 in a Mercedes-Benz cause further damage?
- Continuing to drive with the code may lead to poor engine performance, increased fuel consumption, and potential long-term damage to the fuel system.
8. Will resetting the OBDII code P0191 in a Mercedes-Benz make it go away permanently?
- Resetting the code may temporarily turn off the check engine light, but the underlying issue causing the code will need to be addressed to prevent it from reoccurring.
9. How much does it typically cost to repair the OBDII code P0191 in a Mercedes-Benz?
- Repair costs can vary depending on the exact cause of the issue, but replacing a faulty fuel rail pressure sensor can range from $150 to $300 including parts and labor.
10. Can a Mercedes-Benz dealership help diagnose and repair the OBDII code P0191?
- Yes, a Mercedes-Benz dealership or qualified mechanic with experience in diagnosing and repairing fuel system issues can help address the P0191 code effectively.
Discuss the causes and fixes for P0191 Mercedes-Benz OBDII Code
-
Went to a shop to resolved the P0191 code problem. Couple hours later, my Engine Light came back on? What would cause it to Come Back on Again? Puzzle...Elaine Y-I
-
Looks like the shop didn't actually fixed the problem, just cleared the light. Did they replaced any parts? I suggest taking back you vehicle to the shop and have them fix the problem.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
