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DTC codes / P27xx · Transmission / P27B5

P27B5Internal Control Module Transmission Gear Ratio Control Performance

P27B5 is a generic powertrain code that indicates the transmission control module (TCM) has detected an internal performance fault within its own gear ratio control strategy. The TCM monitors the actual gear ratio by comparing input and output speed sensors, and when the commanded ratio does not match the achieved ratio within a calibrated threshold, it stores this code because the control module itself is suspect.

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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