The OBD2 code P051B indicates a problem with the crankcase pressure sensor circuit range/performance. This sensor monitors the pressure inside the engine’s crankcase, and deviations from normal ranges can indicate issues like leaks or problems with the engine’s ventilation system. It’s a crucial aspect of maintaining engine health, as improper crankcase pressure can lead to engine performance issues, including power loss and irregular operation.
P051B quick overview
| Meaning | P051B: Crankcase Pressure Circuit Range/Performance |
| Is it serious? | Yes, as it can lead to significant engine performance issues and, over time, cause engine damage. |
| Possible causes | – Faulty crankcase pressure sensor – Leaks in the crankcase ventilation system – Damaged hoses – Damaged wiring – Worn out engine’s internal components. |
| How to diagnose? | Inspect the crankcase pressure sensor and wiring for damage. Perform a smoke test to identify any leaks in the crankcase ventilation system. Check for damaged or cracked hoses that could affect pressure. Evaluate the engine’s internal components for issues that could influence crankcase pressure. |
P051B Meaning
In simpler terms, think of the P051B code like a warning that there’s a problem with the pressure inside your engine’s crankcase, the space below where all the engine’s moving parts are. If the pressure there isn’t right, it can cause your engine to act up, losing power or running poorly.
This could be because of a sensor that’s not working right, leaks in the system that keeps the engine’s insides clean, or even problems with the engine itself. It’s like noticing your home’s air conditioning is always on; it points to a bigger issue that needs fixing.
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How to fix P051B – learn from mechanics
I looked into P051B service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Dodge
Vehicle information 2008 Dodge Ram 2500 Laramie 6.7L
Issue + repair history
- Customer experienced loss of power and excessive gray smoke.
- Engine would not rev past 1000rpm.
- Initial scan revealed codes: P051B, P245A, P1508, P1506, P2580.
- Replaced plugged crankcase filter and flashed PCM for recall.
- Smoke and inability to rev persisted.
- Exhaust system and EGR system checked for blockages.
- Fuel quality inspected.
- Turbo speed PID showed 0 while turbo observed spinning.
- Turbo sensor replaced, no change.
- Grounds checked and PCM connections inspected.
- Oil and coolant levels verified.
- Engine warranty previously voided due to fuel contamination.
Other OBD2 Codes + Test Results
- P051B – Crankcase pressure circuit
- P245A – EGR bypass control circuit open
- P1508 – Crankcase filter replace
- P1506 – Crankcase pressure depression regulator valve performance
- P2580 – Turbo speed sensor performance
Mechanic suggestions
- Recommended checking fuel pressure, injection timing, and air intake for proper function.
- Advised pulling fuel and oil samples and checking lift pump volume and injection pump pressure.
- Suggested inspecting turbo for carbon buildup and proper operation.
- Urged testing fuel for gasoline contamination.
- Proposed checking recent oil change and ensuring proper oil grade and level.
- Recommended inspecting turbo for carbon buildup and actuator function.
- Speculated on potential issues related to incorrect oil type or overfilling.
- Suggested checking turbo for carbon buildup and throttle body for correct operation.
- Raised concerns about incorrect oil viscosity affecting injector pressure and timing.
- Asked if crankcase was overfilled, which could impact injector operation.
Final fix Discovered contaminated fuel as the root cause of the issue. After switching to different fuel, the truck’s performance improved, and smoke dissipated.
Case #2: Dodge
Vehicle information 2009 Dodge Ram 5500 SLT 6.7L
Issue + repair history
- Cranks but does not start initially.
- Aftermarket add-ons include EGR delete and H&S tuner.
- Loose fitting found at fuel rail for #3 injector line.
- Multiple fittings not torqued properly.
- Misfires and black smoke observed during test drive.
- Replaced all 6 injectors due to fuel bleed down.
- Vehicle still experiencing lack of power and stalling after running for 10 minutes.
Other OBD2 Codes + Test Results
- P0101: MAF performance
- P051b: Crankcase pressure circuit range/performance
- P2262: Turbo boost not detected/mechanical
- P2609: Intake air heater system performance
Mechanic suggestions
- Recommend checking for boost leaks and exhaust restrictions.
- Suggest inspecting turbocharger assembly for sticking vanes.
- Propose restoring vehicle to stock configuration if feasible.
- Advised proper testing of fuel system components.
Final fix Replaced turbocharger assembly.
Thank you for clarifying. Let’s proceed with formatting the next case according to the provided template. Please provide the details of the second forum post for formatting.
Case #3: Ford
Vehicle information
- Vehicle make, model, year: Ford F-150 2015
- Engine: 3.5L V6 EcoBoost
Issue + repair history
- Customer complained of intermittent loss of power during acceleration.
- Previous repair history:
- Replaced spark plugs and ignition coils.
- Cleaned mass airflow sensor (MAF).
- Checked and replaced faulty fuel injectors.
Other OBD2 Codes + Test Results
- OBD2 codes:
- P051B: Crankcase Pressure Circuit Range/Performance
Mechanic suggestions
- Check for vacuum leaks in the crankcase ventilation system.
- Inspect the crankcase pressure sensor and its wiring harness for any signs of damage or corrosion.
- Perform a smoke test to identify any leaks in the crankcase ventilation system.
- Verify the operation of the crankcase ventilation valve.
Final fix
- Upon inspection, found a cracked hose in the crankcase ventilation system, causing intermittent pressure fluctuations.
- Replaced the cracked hose and cleared the OBD2 trouble code.
- Test drove the vehicle, and the issue of power loss during acceleration was no longer present.
How to diagnose P051B
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Inspect crankcase pressure sensor and wiring | Look for damage or disconnections that could impair sensor function. |
| Perform smoke test | Identify leaks in the crankcase ventilation system. |
| Check for damaged or cracked hoses | Leaks can lead to incorrect pressure readings. |
| Evaluate engine’s internal components | Internal issues can affect crankcase pressure and performance. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko