Code Definition

P0899 — Transmission Control System MIL Request Circuit High

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

About P0899

P0899 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 P0899 is stored, the module has detected a signal or supply voltage higher 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 P0899 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 P0899 fault code is set when the transmission control module (TCM) detects a high voltage condition in the circuit responsible for triggering the Malfunction Indicator Lamp (MIL) or 'check engine' light. This indicates an electrical issue in the circuit that communicates with the vehicle's onboard diagnostic system to activate the MIL, specifically pointing to a high voltage situation. The MIL request circuit is an essential communication link used by the TCM to notify the driver of transmission-related faults via the dashboard warning indicator. A high voltage condition in this circuit ca...

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