Mazda Roadster B1566 Engine Trouble Code
What is Mazda Roadster B1566?
Mazda Roadster B1566 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.
B1566 on the Mazda Roadster
A known issue on the Mazda Roadster is that aftermarket air filter upgrades can inadvertently trigger B1566. High-flow filters alter the intake resonance frequency, causing the MAP sensor to report pressure readings outside factory calibration.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Mazda Roadster |
| Brand: | Mazda |
| Model: | Roadster |
| Code: | B1566 |
B1566 Mazda Roadster Symptoms
Check Engine Light
Illuminated Mazda Roadster dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Mazda Roadster
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Mazda Roadster
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 Mazda Roadster B1566
Diagnostic Steps:
Regarding B1566, 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:
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.
Mazda Roadster B1566 Repair Cost
For Mazda Roadster owners, budget the following for a B1566 repair: EGR valve cleaning $80–$120 or replacement $250–$450, intake manifold gasket $120–$200, and a post-repair reset and road test. Total: $350–$650 at an independent garage.
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 Mazda Roadster
Some Mazda Roadster models have a known software bug where the PCM flags B1566 after battery disconnection and reconnect. Always perform an ECU adaptation reset and drive cycle before ordering any parts following battery work.
DIY Repair Guide: B1566 on Mazda Roadster
Replacing the spark plugs on the Mazda Roadster is rated a difficulty 2/5 for home mechanics. The top-mounted plug access on this engine requires a 3/8" extension and a 14mm spark plug socket. Always torque to the manufacturer's specification to avoid cracking the cylinder head.
Preventing B1566 on the Mazda Roadster
To keep the Mazda Roadster free of recurring B1566 faults, change the engine oil every 5,000–7,500 miles using a grade specified by Mazda. Oil viscosity directly affects VVT actuator response, and using the wrong grade is one of the most avoidable causes of this code.
Frequently Asked Questions — Mazda Roadster 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 Mazda Roadster.