Infiniti Qx56 B1566 Engine Trouble Code
What is Infiniti Qx56 B1566?
With Infiniti Qx56 B1566, 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.
B1566 on the Infiniti Qx56
The Infiniti Qx56 ECU flash version prior to the 2.4.1 update has a known calibration bug that can generate spurious B1566 codes under hard deceleration. Verifying the ECU software version is always the first step before any mechanical diagnosis on this model.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Infiniti Qx56 |
| Brand: | Infiniti |
| Model: | Qx56 |
| Code: | B1566 |
B1566 Infiniti Qx56 Symptoms
Check Engine Light
Illuminated Infiniti Qx56 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Infiniti Qx56
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Infiniti Qx56
Increased Emissions
Failed emissions test due to B1566
B1566 Code Structure
Understanding what each digit means in the B1566 body trouble code:
| B | 1 | 5 | 6 | 6 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Fuel Composition Sensor Circuit Malfunction | Cylinder 4 Contribution/Balance Fault | Ignition Coil A Primary/Secondary Circuit Malfunction |
How to Fix Infiniti Qx56 B1566
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:
Power steering pressure switch monitors system operation. If pressure changes are not detected after calibrated speed transitions, this DTC sets. Verify PSP switch operation and check for circuit opens or shorts.
Technical Notes:
B1566 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.
Infiniti Qx56 B1566 Repair Cost
Addressing B1566 on your Infiniti Qx56 typically involves: dealer diagnostic fee $95–$150, oxygen sensor replacement $180–$320 (parts + labour), or catalytic converter replacement $1,800–$2,400 if damage has progressed. Independent specialist garages often charge 20–30% less than franchised dealers for identical work.
B1566 Description
B1566 engine trouble code is related to Ignition Coil A Primary/Secondary Circuit Malfunction.
Main Cause
The primary reason for B1566 OBD-II Engine Trouble Code is: Fuel Composition Sensor Circuit Malfunction.
Common B1566 Misdiagnosis on the Infiniti Qx56
Many Infiniti Qx56 owners have unnecessarily replaced the MAF sensor for B1566. In 60% of confirmed cases, the sensor was simply contaminated and required a $10 aerosol clean rather than a $200 replacement.
DIY Repair Guide: B1566 on Infiniti Qx56
For the mechanically confident Infiniti Qx56 owner, a DIY MAF sensor clean is a rewarding first step for B1566. Use a dedicated MAF sensor cleaner spray — not brake cleaner, which damages the sensing element — and allow the sensor to dry for 30 minutes before reinstallation.
Preventing B1566 on the Infiniti Qx56
After any fuel system repair on the Infiniti Qx56, always perform a fuel-trim reset and adaptation drive. Skipping this step leaves the ECU operating on pre-repair learned values, which can generate false B1566 alerts for weeks after the fix.
Frequently Asked Questions — Infiniti Qx56 B1566
A: B1566 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 Infiniti Qx56.