Chevrolet Montana U1859 Engine Trouble Code
What is Chevrolet Montana U1859?
With Chevrolet Montana U1859, you may drive for several weeks with a malfunctioning MAF sensor, but expect decreased fuel economy and eventual stalling. Shop replacement costs $240–$400 depending on vehicle. The labour is straightforward, with most cost from the part itself.
U1859 on the Chevrolet Montana
Owners of the Chevrolet Montana should be aware that U1859 can appear alongside oil consumption warnings. Low oil pressure caused by a worn PCV system lets crankcase vapour contaminate the mass air flow sensor, sending erroneous readings to the ECU.
Code Information
| Code Type: | OBD-II Network (U) Trouble Code |
| System: | Network |
| Vehicle: | Chevrolet Montana |
| Brand: | Chevrolet |
| Model: | Montana |
| Code: | U1859 |
U1859 Chevrolet Montana Symptoms
Check Engine Light
Illuminated Chevrolet Montana dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Chevrolet Montana
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Chevrolet Montana
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 Chevrolet Montana U1859
Diagnostic Steps:
Poor running symptoms align with MAP sensor malfunction. In some cases, a faulty MAP sensor will not trigger a code. The issue may represent separate wiring concerns requiring individual diagnosis.
Repair Solution:
Excessive air inflow may result from vacuum leaks, dirty sensors, or EGR valves not closing properly. Insufficient fuel can stem from dirty injectors, clogged filters, weak fuel pump, or leaking pressure regulator.
Technical Notes:
U1859 DTCs can be triggered by upstream issues. For example, a dirty MAF sensor may cause incorrect fuel-trim adjustments, leading oxygen sensors to report mixture problems. Address root causes first.
Chevrolet Montana U1859 Repair Cost
Fuel injector cleaning service on the Chevrolet Montana costs $150–$300 for an ultrasonic bench-clean of all injectors with flow-test certification. On-car induction cleaning is a cheaper ($80–$120) first step but is less thorough for heavily fouled injectors.
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 Chevrolet Montana
When U1859 triggers on the Chevrolet Montana, a flashing check-engine light (as opposed to a steady one) indicates an active misfire. Misfire codes are commonly misdiagnosed as sensor faults; always rule out ignition and fuel delivery issues before testing sensors.
DIY Repair Guide: U1859 on Chevrolet Montana
After any repair that involved disconnecting the battery on the Chevrolet Montana, the power window, steering angle sensor, and transmission adaptive values all require a reset drive cycle. Skipping this can cause false fault codes — including U1859 — for the first two to three start cycles.
Preventing U1859 on the Chevrolet Montana
The Chevrolet Montana coolant temperature sensor plays a role in fuel enrichment during warm-up. Replacing it as a precaution at 80,000 miles ($25–$40 DIY) prevents the faulty cold-start enrichment that can lead to U1859.
Frequently Asked Questions — Chevrolet Montana U1859
A: Clearing the code without repair allows the fault condition to persist. Depending on the cause, this can lead to catalytic converter damage, increased fuel consumption, and secondary component failures that are significantly more expensive to address than the original fault.