Experiencing a frustrating issue with your OBD scanner showing a red light but failing to connect to your Mazda Miata’s computer? You’re not alone. Many Miata owners, especially those with NB models (1999-2005), encounter similar problems when trying to use aftermarket OBD-II scanners. This guide will walk you through the common causes and troubleshooting steps to get your scanner working and reading your Miata’s diagnostic data.
Understanding the OBD-II Port Location on Your Miata
One initial point of confusion, especially for first-time Miata owners, is the location of the OBD-II port itself. While your mechanic might seem to access it from a lower position in the footwell, the primary OBD-II port in your ’99 Miata (NB model) is indeed located above the fuse box to the left of the driver’s left knee. You’ll need to remove the fuse box cover to access it.
Alt text: Accessing the OBD2 port in a Miata NB by removing the fuse box cover located to the left of the steering wheel.
It’s understandable why you might question this location’s convenience, particularly if you intend to use a scan gauge or leave the scanner plugged in while driving. This placement can feel a bit awkward and might lead you to suspect there’s another, more accessible port hidden elsewhere. However, for the NB Miata, this is the standard OBD-II port location.
OBD-II Protocol and Scanner Compatibility with NB Miatas
The next crucial aspect to consider is OBD-II protocol compatibility and whether your chosen scanner is playing nicely with your ’99 Miata. While OBD-II is a standard, some vehicles, particularly in the early years of OBD-II implementation, can be a bit particular about the scanners they communicate with.
When you mention your BAFX Bluetooth OBD-II reader showing a red light, this typically indicates that the scanner is receiving power from the OBD-II port. The red light itself is a good sign that the port is providing power. The problem lies in the data communication between the scanner and your Miata’s Engine Control Unit (ECU).
The “No response from vehicle ECU” error you’re seeing in apps like Torque and Car Gauge Lite suggests a communication breakdown. This could stem from a few potential issues:
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Protocol Mismatch: While most OBD-II scanners, including the BAFX, are designed to automatically detect the correct protocol, sometimes manual protocol selection is needed. Your ’99 Miata uses ISO 9141-2 protocol. While “Auto” should ideally work, try manually selecting ISO 9141-2 within your Torque app settings to see if it establishes a connection.
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Scanner Incompatibility: It’s possible, though less likely with a well-reviewed scanner like the BAFX, that your specific scanner model has compatibility issues with the NB Miata’s OBD-II implementation. Some older vehicles can be finicky with certain aftermarket scanners. The fact that your scanner works perfectly on your ’98 Civic (which is also OBD-II compliant) indicates the scanner itself is functional, but vehicle-specific compatibility remains a possibility.
Alt text: A handheld OBD2 scanner successfully connected and communicating with a car’s Engine Control Unit (ECU) to read diagnostic information.
Troubleshooting Steps When Your OBD Scanner Shows a Red Light
Here’s a systematic approach to troubleshoot why your OBD scanner is showing a red light but not connecting to your Miata:
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Verify OBD-II Port Location: Double-check you are using the correct port above the fuse box. Ensure there are no obstructions or damage to the port.
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Manual Protocol Selection: In your OBD app (Torque, Car Gauge Lite, etc.), delve into the settings and attempt to manually select the ISO 9141-2 protocol. Retry the connection.
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Test with a Different OBD-II App: While you’ve tried Torque and Car Gauge Lite, consider testing with another OBD-II app just to rule out app-specific glitches. There are many free and paid OBD-II apps available on the Google Play Store.
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Try a Different OBD-II Scanner: If possible, borrow or try a different brand or model of OBD-II scanner. This will help you isolate whether the issue lies with your BAFX scanner’s compatibility with your Miata. Sometimes, trying a different scanner, even one in the same price range, can resolve compatibility hiccups.
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Check for Blown Fuses (Less Likely but Possible): Although the red light indicates power, it’s worth quickly checking the fuses related to the OBD-II port or ECU, just to be completely thorough. Consult your Miata owner’s manual for fuse box diagrams and relevant fuse locations.
Conclusion: Getting Your OBD Scanner to Connect
Seeing a red light on your OBD scanner but no connection to your Miata can be frustrating, but it’s a solvable problem. By systematically checking the OBD-II port location, experimenting with manual protocol selection, and potentially trying a different scanner, you should be able to pinpoint the cause. NB Miatas, while OBD-II compliant, can sometimes be a bit sensitive to scanner compatibility. Don’t hesitate to explore different scanner brands and models to find one that reliably connects to your ’99 Miata and unlocks the valuable diagnostic information it holds.
