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All codes/P27B5

P27B5

Internal Control Module Transmission Gear Ratio Control Performance

High severity

The internal gear ratio control logic in the transmission control module does not produce the expected commands.

The internal gear ratio control logic in the transmission control module does not produce the expected commands.

Common causes

  • Internal software logic fault

    One of the most commonly reported causes for this code — check this first.

    high

    Typical part cost: $220-1650

  • Memory corruption in TCM

    A plausible cause — test and verify before replacing parts.

    medium

    Typical part cost: $220-1650

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First things to check

  1. 1Confirm the code with a scan tool and check for additional related codes.
  2. 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

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Tools you may need

Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.

Illustration of a Bluetooth OBD2 adapter, not a product photo

Basic checks

Veepeak OBDCheck BLE

A Bluetooth LE adapter for reading standard engine codes and supported live data.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Regular diagnostics

vgate iCar Pro BLE 4.0

A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.

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Illustration of a Bluetooth OBD2 adapter, not a product photo

Another option

OBDLink CX

A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.

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Illustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.

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Related codes

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Frequently asked questions

What does P27B5 mean?

P27B5 means "Internal Control Module Transmission Gear Ratio Control Performance". It is a generic OBD-II code that points to a fault in the cylinder contribution / balance.

What are the most common causes of P27B5?

internal software logic fault; memory corruption in tcm — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

This code points to a problem that can cause damage or affect safety. Avoid driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.

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