OBD-II trouble code
U0402: Invalid Data Received from Transmission Control Module
A module is receiving messages from the transmission control module (TCM), but the data is implausible or out of range. The connection is alive — the content is wrong. Often a sensor, calibration, or internal fault driving bad data, or a network issue corrupting it.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,200
- DIY difficulty
- Shop recommended
What does U0402 mean?
U0402 is different from a 'lost communication' code. Here the receiving module is still hearing from the transmission control module (TCM) — the connection is alive — but the data inside those messages is invalid: a value is out of its expected range, implausible, missing, or conflicts with what other sensors report. The messenger is talking, but what it's saying doesn't make sense, so the receiving module rejects the data and stores U0402.
Because the problem is the content of the data rather than the link itself, the causes lean toward whatever makes the TCM send bad information. A failing or out-of-range transmission sensor — an input or output speed sensor, a fluid temperature sensor, or a pressure switch — can cause the TCM to broadcast an implausible value. The TCM's calibration or software can be at fault: outdated, corrupted, or mismatched after a module was replaced or flashed without proper programming. The TCM itself can have an internal fault. There are usually accompanying transmission codes that point at the specific signal that's wrong, and those should be read and addressed first because they often identify the real root cause. Network problems can still play a role: electrical noise, a marginal bus, wiring issues, or low system voltage can corrupt otherwise-good messages or make a module report implausible data.
The symptoms depend on which data is invalid. You may see harsh or erratic shifting, a transmission that defaults to a fail-safe or limp mode, a speedometer or gauge that misbehaves because it depends on TCM data, or stability and cruise-control features that disable themselves because they can't trust the transmission information they need. Often U0402 is a secondary code — it's the receiving module complaining about bad data that another transmission code explains. The car is usually still driveable, but because the underlying fault can affect how the transmission behaves, U0402 should be diagnosed by reading the full code set and finding what's actually producing the bad data.
Common causes
- Failing or out-of-range transmission sensor feeding the TCM (speed, temperature, pressure)
- Accompanying transmission fault producing the invalid value
- Outdated, corrupted, or mismatched TCM calibration/software
- TCM internal fault
- Low system voltage causing implausible data
- Electrical noise or a marginal bus corrupting messages
- TCM replaced or flashed without proper programming
- Wiring or connector issue degrading signal quality
Symptoms
- Harsh, erratic, or delayed shifting
- Transmission in a fail-safe or limp mode
- Speedometer or gauges misbehaving (they rely on TCM data)
- Cruise control or stability features disabling themselves
- Multiple related transmission codes stored alongside U0402
- Intermittent symptoms tied to a specific operating condition
- Car generally still driveable
Diagnostic steps
- 1.Read ALL stored codes first — U0402 is often secondary to a transmission code that names the bad signal.
- 2.Address any companion transmission or sensor codes, since they frequently identify the root cause.
- 3.Check system voltage and the battery/charging system; low voltage can cause implausible data.
- 4.Verify the TCM has the correct, current calibration — especially if a module was recently replaced or flashed.
- 5.Inspect bus wiring and connectors for damage or noise sources that could corrupt messages.
- 6.Use live data to compare the questioned value against actual conditions; confirm the failing sensor or the TCM before replacing anything.
Repair cost
$100 – $1,200
Cost depends entirely on what's producing the bad data. A failing transmission sensor is often $150-$500 including diagnosis. Correcting low voltage or a charging fault runs $150-$600. A calibration update/reflash is typically $100-$300. TCM replacement and programming is the expensive case at $600-$1,200+ but should only follow thorough diagnosis. Because U0402 is frequently a secondary code, fixing the companion fault often clears it.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.