Infiniti M35 B1566 Engine Trouble Code
What is Infiniti M35 B1566?
With Infiniti M35 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 M35
In cold climates, Infiniti M35 vehicles frequently log B1566 during the first winter of ownership. Condensation inside the throttle body creates a temporary short circuit in the position sensor wiring, which clears once the engine warms up — but the fault code remains stored.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Infiniti M35 |
| Brand: | Infiniti |
| Model: | M35 |
| Code: | B1566 |
B1566 Infiniti M35 Symptoms
Check Engine Light
Illuminated Infiniti M35 dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Infiniti M35
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Infiniti M35
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 M35 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:
VSS concerns may stem from noisy input signals caused by RFI/EMI from ignition wires, charging circuits, or aftermarket equipment. Verify VSS reads 0 mph when transmission is in Park.
Technical Notes:
B1566 DTC specifically relates to camshaft timing. When cam timing is over-retarded, the check-engine light illuminates and this code sets. Verify VCT solenoid operation and check for contamination.
Infiniti M35 B1566 Repair Cost
Throttle body cleaning and idle relearn on the Infiniti M35 for a B1566 diagnosis costs $60–$100 at an independent shop. If a full throttle body replacement is needed (rare), expect $250–$450 including programming the unit to the ECU.
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 M35
A catalytic converter is often condemned on the Infiniti M35 when B1566 appears and an efficiency code is present. Before replacement, verify that the upstream oxygen sensor is not slow-responding — a lazy O2 sensor mimics catalytic inefficiency perfectly.
DIY Repair Guide: B1566 on Infiniti M35
Replacing the oxygen sensor on the Infiniti M35 requires an O2 sensor socket (22mm or 7/8") and penetrating oil applied 24 hours in advance. On vehicles over five years old, the sensor threads often corrode into the bung; heat from a propane torch (briefly applied) is usually sufficient to free them.
Preventing B1566 on the Infiniti M35
Inspecting the Infiniti M35 wiring harness conduit grommets annually — especially the floor pan grommet — costs nothing and takes 10 minutes. Catching moisture ingress early eliminates the most common electrical trigger for B1566 on this model.
Frequently Asked Questions — Infiniti M35 B1566
A: Not always. Across model years, Infiniti revised sensor specifications, wiring paths, and ECU calibrations. Always confirm the repair procedure matches your specific vehicle's production year and engine code, as parts and labour times can vary significantly.