U0402 Invalid Data Received From Transmission Control Module

U0402 means the transmission control module is talking, but the data it is sending fails a plausibility check. Communication is intact — the content is wrong, out of range, or inconsistent with what other modules report.

Code details

Generic OBD-II · U0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not chase the network wiring for this one. The bus is working — that is what separates an invalid-data code from a lost-communication code — so the fault lies in what the transmission control module is measuring or computing.

Symptoms of U0402

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of U0402

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Read the stored codes inside the transmission control module itself, because the reason its data is implausible is usually a fault it has already recorded against one of its own sensors.
Compare the suspect value against the same quantity as other modules see it, since a plausibility failure is a disagreement between sources rather than a missing signal.
Check the sensors feeding the sending module along with their wiring and grounds, because a skewed or intermittent input produces valid messages carrying invalid numbers.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.