U0402

Invalid Data Received From TCM

Network / communication Generic OBD-II Medium

What it means

U0402 means a module is receiving data from the transmission control module (TCM) that is out of range or implausible. The transmission often responds by dropping into limp/fail-safe mode — a single fixed gear with harsh or missing shifts. You can usually limp a short distance to a shop, but avoid extended driving until the TCM wiring, sensors, or software are checked.

Medium

Can I keep driving? Short trips only — the transmission may drop into limp/fail-safe (one fixed gear) with harsh or no shifting; you can usually limp to a shop but don't tow or drive far.

Real-world scan data

Seen in

896

scans in the past year

Found in

0.1%

of scans

0.2%

of scans that found faults

Appears alongside · share of U0402 scans

U0101in 66.5% of scans

C1050in 57.7% of scans

U0001in 57.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Transmission warning light on, often with reduced-power mode
Harsh, delayed, or no shifting; stuck in a single gear (limp mode)
Speedometer or gear indicator behaving oddly
Other modules storing 'lost communication' or 'invalid data' codes for the TCM

Common causes

Most likely first

TCM broadcasting out-of-range or implausible values onto the CAN busLikely
Internal TCM fault or corrupted softwareCommon
Wiring, connector, or ground fault at the TCM corrupting bus dataCommon
Transmission sensor feeding the TCM impossible readingsLess often

How to diagnose & fix

Work through it in order

Scan all modules and record every stored code, including companion communication codes.
Check TCM power, grounds, and connector integrity.
Inspect TCM and transmission harness wiring for damage or corrosion.
Verify TCM software is correct; reflash or replace and program if internally failed, then clear and re-test.

FAQ

Quick answers

Is it safe to drive with U0402?+

Only briefly. The transmission may go into limp mode — a single fixed gear with harsh shifts — which is enough to reach a shop but not for normal driving. Prolonged driving risks transmission damage.

Can I just clear U0402?+

It returns until the fault is repaired. The TCM is still reporting invalid data, so the wiring, sensor, or module problem must be fixed first.

Read & clear U0402 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX