P27B6
Internal Control Module Transmission Speed Sensor Performance
The internal speed sensor processing logic in the transmission control module produces implausible results.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: hard
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Internal software logic faultCommon
- Aged input capture circuitry driftsPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- TCM
- Speed Sensors
P27B6 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.