Land Rover DC-DC Converter DTCs: Fault Codes Explained

Decoding Land Rover DC-DC Converter Fault Codes (DTCs)

When a technician connects a diagnostic scanner to your MHEV Land Rover with a charging fault, they're looking for specific Diagnostic Trouble Codes (DTCs) stored in the Generator Control Module (GCM) or Powertrain Control Module (PCM). These codes provide clues to the root of the problem. Here are some common DTCs related to a failing 48V to 12V DC-DC converter.

Common DC-DC Converter Related DTCs

(Note: Specific code descriptions can vary slightly by model and diagnostic tool. This is a general guide.)

• P0A9E-00 / P0A9E-19 – Generator Control Module – Over Temperature: This code indicates that the DC-DC converter has exceeded its safe operating temperature. While this could be caused by an external factor like a blocked cooling vent, it often points to an internal failure within the converter causing it to overheat.
• P0D22-16 / P0D22-17 – Generator Control Module – Circuit Voltage Below / Above Threshold: This is a very common code set. The module's internal diagnostics have detected that its output voltage is either too low (most common, indicating it has stopped charging) or too high. This almost always signifies an internal failure of the converter.
• P0D25-00 – Generator ‘B' Control Circuit Low: The system has detected low voltage on the control circuit for the converter, pointing towards an internal electrical fault.
• U012A-00 – Lost Communication With Generator Control Module: This code means that other modules on the vehicle's network (like the PCM or BCM) can no longer communicate with the DC-DC converter. This can happen if the converter has lost power or has suffered a total internal electronic failure.

How to Interpret These Codes

While a single code might appear in isolation, it's common to see a combination of these DTCs when a DC-DC converter fails. For example, a “Lost Communication” code paired with a “Circuit Voltage Below Threshold” code is a very strong indication that the converter itself has failed and needs to be replaced.

The Next Step After Diagnosis

These fault codes are the electronic ‘proof' that a component has failed. Once a technician has confirmed one or more of these codes are present and has ruled out external wiring issues, the definitive repair is to replace the faulty DC-DC converter with a new, genuine Land Rover unit.

SX-Tool provides the genuine parts needed to clear these codes and restore your vehicle's charging system.