Can an OBD2 Scanner Check an Alternator?

An OBD2 scanner is a valuable tool for diagnosing car problems, but can it check your alternator? The answer isn’t as simple as a yes or no. Here’s what you need to know about OBD2 scanners and alternator checks.

Understanding OBD2 Scanners and Alternators

OBD2 scanners work by reading diagnostic trouble codes (DTCs) stored in your vehicle’s onboard computer. These codes are triggered when the computer detects a problem within a system. The alternator, responsible for charging the battery and powering electrical components, plays a crucial role in your car’s electrical system.

How OBD2 Scanners Can Indirectly Check Alternators

While an OBD2 scanner can’t directly measure alternator output, it can detect voltage irregularities that may indicate an alternator issue. Here’s how:

• Battery Voltage Readings: Most OBD2 scanners display live data, including battery voltage. A healthy charging system should show around 14 volts with the engine running. Significant deviations, like consistently low voltage (under 13 volts) or excessively high voltage (over 15 volts), can point to a failing alternator.
• Charging System DTCs: While not all alternator problems trigger specific codes, some common DTCs related to the charging system include:
  • P0562 – System Voltage Low
  • P0563 – System Voltage High
  • P0117 – Coolant Temperature Sensor Circuit Low Input (can be related to a faulty alternator affecting sensor readings)

Limitations of OBD2 Scanners in Alternator Diagnosis

It’s important to understand that OBD2 scanners offer an indirect approach to alternator diagnosis. They can highlight potential charging system issues, but further testing is necessary to confirm a faulty alternator.

• No Direct Output Measurement: OBD2 scanners don’t directly measure the alternator’s output current. A dedicated multimeter is required for that purpose.
• DTCs Can Be Misleading: Charging system DTCs can be triggered by problems other than a bad alternator, such as a loose battery connection, a faulty voltage regulator, or a wiring issue.

When to Seek Professional Help

If your OBD2 scanner reveals voltage irregularities or charging system DTCs, it’s crucial to consult a qualified mechanic. They have the expertise and specialized equipment to accurately diagnose the root cause of the problem and recommend the appropriate solution, whether it’s alternator replacement or another electrical system repair.

Conclusion

While an OBD2 scanner can’t directly check your alternator, it serves as a valuable tool for detecting voltage fluctuations and charging system codes that might suggest an alternator problem. Remember, an OBD2 scanner is a starting point for diagnosis, and professional inspection is always recommended to confirm and address the underlying issue.