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DTC codes / P27xx · Transmission / P27B4

P27B4Internal Control Module Transmission Gear Direction Control Performance

P27B4 is a manufacturer-specific powertrain code indicating that the transmission control module (TCM) has detected an internal performance fault in its own gear direction control circuitry, meaning the module cannot reliably command or verify the selection of forward, reverse, or neutral. The TCM compares its internal commands with feedback from the gear direction control system and sets this code when the expected state does not match the actual state within a calibrated time window.

SystemPowertrain
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaTransmission

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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