Code Definition

P2500 — Low Signal Voltage On Generator Turn ON Signal Circuit

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P2500

P2500 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P2500 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P2500 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The engine or body control module sets DTC P2500 when it detects an abnormally low voltage on the generator turn on signal circuit. This circuit is the command line the module uses to switch the alternator on and bring it into charging, and the module monitors the line to confirm the commanded state. A low signal voltage points to a short to ground, high resistance, or a loss of supply on that circuit. When this code is set the alternator may not turn on or may charge erratically, the battery or charge warning light can illuminate, and a discharged battery or low system voltage driveability fa...

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