Bmw 320 P1799 Engine Trouble Code
What is Bmw 320 P1799?
When Bmw 320 P1799 code appears, first check your gas cap. Pull over safely, ensure it is tight, and inspect for cracks. A loose or damaged gas cap affects fuel-system pressure and emissions. A replacement cap costs about $3–$10. This simple fix can resolve the code and improve fuel economy.
P1799 on the Bmw 320
Independent workshop data shows that Bmw 320 vehicles with P1799 resolve approximately 40% of cases after a throttle body cleaning and idle relearn procedure. This is always the recommended first step before investing in new sensors.
Code Information
| Code Type: | OBD-II Powertrain (P) Trouble Code |
| System: | Powertrain |
| Vehicle: | Bmw 320 |
| Brand: | Bmw |
| Model: | 320 |
| Code: | P1799 |
P1799 Bmw 320 Symptoms
Check Engine Light
Illuminated Bmw 320 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Bmw 320
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Bmw 320
Increased Emissions
Failed emissions test due to P1799
P1799 Code Structure
Understanding what each digit means in the P1799 powertrain trouble code:
| P | 1 | 7 | 9 | 9 |
|---|---|---|---|---|
| Powertrain Code | Fuel And Air Metering | Fuel Rail Pressure Sensor Circuit Malfunction | Crankshaft Position Sensor A Circuit Malfunction | Reverse Input Circuit |
How to Fix Bmw 320 P1799
Diagnostic Steps:
Oxygen sensors measure exhaust gas oxygen content to optimise air-fuel ratio. This optimisation improves fuel economy and reduces emissions. Sensors degrade over time and require periodic replacement.
Repair Solution:
Firing order is engineered to minimise vibration. Altering firing order results in mistimed ignition and poor engine operation. Consult vehicle-specific repair manual for correct firing order.
Technical Notes:
P1799 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
Bmw 320 P1799 Repair Cost
A Bmw 320 P1799 fault caused by ignition coil failure costs roughly $90–$160 per coil including labour. Replacing all coils simultaneously — rather than one at a time — is recommended because coils typically age at similar rates. This preventive approach keeps total cost below $500.
P1799 Description
P1799 engine trouble code is related to Reverse Input Circuit.
Main Cause
The primary reason for P1799 OBD-II Engine Trouble Code is: Fuel Rail Pressure Sensor Circuit Malfunction.
Common P1799 Misdiagnosis on the Bmw 320
On the Bmw 320, the EGR cooler is sometimes replaced for P1799 when the EGR valve position sensor is at fault. The two components share a fault pathway in older scan tools that do not display live EGR valve position data.
DIY Repair Guide: P1799 on Bmw 320
The throttle body on the Bmw 320 can be cleaned without full removal. Use a clean rag and throttle body cleaner spray with the engine off and cool. After cleaning, an idle relearn is mandatory: disconnect the battery for 10 minutes, reconnect, and allow the engine to idle for 10 minutes undisturbed.
Preventing P1799 on the Bmw 320
Using only genuine or OEM-specification fuel injectors in the Bmw 320 ensures precise spray pattern and flow rate. Inferior aftermarket injectors are a documented trigger for P1799 through off-target fuel delivery.
Frequently Asked Questions — Bmw 320 P1799
A: Almost certainly yes. Most faults that trigger P1799 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.