Napier 40 B1805 Engine Trouble Code
What is Napier 40 B1805?
Napier 40 B1805 code can indicate a faulty oxygen sensor, which may eventually damage the catalytic converter (repair cost: $2,000–$2,200). Professional diagnosis costs around $200–$210. Oxygen sensors are often straightforward to replace — check your owner's manual for location and instructions. This issue should be addressed promptly to prevent further damage.
B1805 on the Napier 40
On high-mileage Napier 40 examples, B1805 is often the first sign of a failing fuel pressure regulator. Residual fuel pressure bleeds off overnight, causing lean-start conditions that the ECU registers as a fault at the next cold start.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Napier 40 |
| Brand: | Napier |
| Model: | 40 |
| Code: | B1805 |
B1805 Napier 40 Symptoms
Check Engine Light
Illuminated Napier 40 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Napier 40
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Napier 40
Increased Emissions
Failed emissions test due to B1805
B1805 Code Structure
Understanding what each digit means in the B1805 body trouble code:
| B | 1 | 8 | 0 | 5 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Engine Oil Temperature Sensor Malfunction | Cold Start Injector 1 Malfunction | Crankshaft Position Sensor B Circuit Malfunction |
How to Fix Napier 40 B1805
Diagnostic Steps:
Regarding B1805, carefully inspect the wire harness near the intake manifold bracket, best accessed from below near the oil filter. Look for chafing, pinching, or damaged insulation.
Repair Solution:
Brake switch circuit concerns may involve open or shorted BPP circuits, damaged switches, or misadjustment. Verify stoplight function and follow proper self-test procedures per service manual.
Technical Notes:
B1805 DTC indicating a sensor fault does not always mean the sensor itself is bad. The issue may stem from the systems being monitored or even the sensor wiring. Proper diagnosis is essential.
Napier 40 B1805 Repair Cost
For Napier 40 owners, budget the following for a B1805 repair: EGR valve cleaning $80–$120 or replacement $250–$450, intake manifold gasket $120–$200, and a post-repair reset and road test. Total: $350–$650 at an independent garage.
B1805 Description
B1805 engine trouble code is related to Crankshaft Position Sensor B Circuit Malfunction.
Main Cause
The primary reason for B1805 OBD-II Engine Trouble Code is: Engine Oil Temperature Sensor Malfunction.
Common B1805 Misdiagnosis on the Napier 40
On the Napier 40, the VANOS (variable camshaft timing) solenoid is routinely replaced for B1805 when the actual issue is oil pressure insufficiency. No solenoid will operate correctly if the oil pressure required to actuate the VVT phaser is not present.
DIY Repair Guide: B1805 on Napier 40
When replacing sensors on the Napier 40, always use anti-seize compound on the thread and dielectric grease on the electrical connector. This simple habit prevents the most common causes of sensor-related callbacks after repair.
Preventing B1805 on the Napier 40
The Napier 40 benefits from an intake manifold decarbonisation at 50,000-mile intervals when direct injection is fitted. Carbon build-up on intake valve stems restricts airflow and creates the lean conditions that trigger B1805.
Frequently Asked Questions — Napier 40 B1805
A: Almost certainly yes. Most faults that trigger B1805 cause the ECU to operate in open-loop mode or apply overly rich fuel trims, both of which increase fuel consumption by 5–15%. Resolving the fault promptly pays for itself in fuel savings over time.