Bmw M6 U1859 Engine Trouble Code
What is Bmw M6 U1859?
Bmw M6 U1859 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.
U1859 on the Bmw M6
Many Bmw M6 drivers first encounter U1859 as a result of worn ignition coil packs. The design of the Bmw engine bay can trap heat near these components, accelerating wear beyond the typical service interval.
Code Information
| Code Type: | OBD-II Network (U) Trouble Code |
| System: | Network |
| Vehicle: | Bmw M6 |
| Brand: | Bmw |
| Model: | M6 |
| Code: | U1859 |
U1859 Bmw M6 Symptoms
Check Engine Light
Illuminated Bmw M6 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Bmw M6
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Bmw M6
Increased Emissions
Failed emissions test due to U1859
U1859 Code Structure
Understanding what each digit means in the U1859 network trouble code:
| U | 1 | 8 | 5 | 9 |
|---|---|---|---|---|
| Network Code | Fuel And Air Metering | Engine Oil Temperature Sensor Malfunction | Cylinder 1 Injector Circuit Low | Reverse Input Circuit |
How to Fix Bmw M6 U1859
Diagnostic Steps:
Regarding U1859, 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:
Crankshaft position sensor signals the computer for precise ignition and fuel injection timing. Faulty sensors cause rough running and reduced efficiency. Modern vehicles enter limp mode and illuminate the check-engine light.
Technical Notes:
Parts or components should not be replaced based solely on U1859 DTC. Consult your vehicle service manual for proper diagnostic procedures, possible causes, and required testing before replacement.
Bmw M6 U1859 Repair Cost
VVT actuator replacement on the Bmw M6 for U1859 is a more significant investment: $400–$700 including the oil flush required before fitting the new actuator. Using the correct low-SAPS engine oil after the repair is critical to prevent premature re-failure.
U1859 Description
U1859 engine trouble code is related to Reverse Input Circuit.
Main Cause
The primary reason for U1859 OBD-II Engine Trouble Code is: Engine Oil Temperature Sensor Malfunction.
Common U1859 Misdiagnosis on the Bmw M6
On Bmw M6 vehicles, the turbo boost solenoid and the MAP sensor feed into the same diagnostic path. U1859 caused by a faulty boost solenoid is sometimes charged to the customer as a MAP sensor replacement, doubling unnecessary parts spend.
DIY Repair Guide: U1859 on Bmw M6
Clearing U1859 on your Bmw M6 with a basic OBD-II reader ($20–$40) is straightforward: plug the reader into the diagnostic port under the dashboard, read the stored code, and clear it. If it returns within one drive cycle, the underlying fault is still present and requires attention.
Preventing U1859 on the Bmw M6
Transmission fluid degradation on the Bmw M6 directly affects solenoid operation. Replacing ATF at 40,000-mile intervals (rather than the often-quoted 'lifetime fill' recommendation) is the best insurance against shift-solenoid codes including U1859.
Frequently Asked Questions — Bmw M6 U1859
A: U1859 is a standardised OBD-II code that can appear on any make and model. However, the specific components and circuits that trigger this code, and the repair procedures involved, vary significantly between vehicles. The information on this page is focused on the Bmw M6.