OBD-II trouble code
U0456: Invalid Data Received From Coolant Temperature Control Module
A module is receiving messages from the coolant temperature control module, but the data inside them is implausible or out of range. The link is alive; the content is wrong. Because this data drives cooling and warm-up decisions, address it before it leads to poor temperature control or overheating.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $90 – $800
- DIY difficulty
- Intermediate DIY
What does U0456 mean?
The coolant temperature control module manages the engine's thermal system — coordinating the electric or map-controlled thermostat, coolant pump, and cooling fans, and reporting coolant temperature to the rest of the network so the ECM and other modules can make fueling, cooling, and warm-up decisions. On modern vehicles this function may live in its own module or be integrated into a broader thermal-management controller. U0456 sets when a receiving module is still hearing from the coolant temperature control module, but the data in its messages is invalid: a value is out of range, implausible, or contradicts what other modules see. The link is alive; the content simply can't be trusted — the defining difference from a lost-communication code, where the module has gone completely silent.
Invalid data here matters because so many systems depend on trustworthy coolant temperature. If the number can't be believed, the vehicle typically falls back to a conservative strategy — running the cooling fans more aggressively, holding a richer warm-up mixture, or capping performance — to protect the engine. That protects hardware but can cause faster fan operation, slower cabin warm-up, reduced fuel economy, and a check engine light. Common causes cluster around whatever corrupts the module's data or its network link: low system voltage or a poor ground; corroded, loose, or damaged connectors; chafed or damaged bus wiring; a failing coolant temperature sensor feeding the module bad readings; and software or configuration problems after a module replacement or update. Because a genuine cooling fault can eventually lead to overheating, U0456 is worth addressing promptly rather than living with the light.
Symptoms center on the check engine light with U0456 stored, cooling fans that run more or run constantly, a temperature gauge that reads erratically or defaults to a fixed position, longer warm-up times, and sometimes companion powertrain or thermal-management codes. The car will usually still drive, but confirm the actual coolant temperature with a scan tool or infrared thermometer before assuming the reading you see on the dash is real — and stop driving if the engine is genuinely overheating.
Common causes
- Low system voltage, a weak battery, or a poor ground at the module
- Corroded, loose, or damaged connectors at the module or coolant temperature sensor
- Chafed or damaged bus wiring corrupting messages in transit
- Failing coolant temperature sensor feeding the module implausible readings
- Coolant temperature control module replaced or updated without correct configuration
- Outdated, corrupted, or mismatched module software
- Water or coolant intrusion at a connector
- Internal coolant temperature control module fault
Symptoms
- Check engine light on with U0456 stored
- Cooling fans running more aggressively or constantly
- Temperature gauge reading erratically or stuck at a default position
- Longer engine warm-up and reduced fuel economy
- Companion powertrain or thermal-management codes stored alongside U0456
Diagnostic steps
- 1.Read all stored codes and note any companion coolant-sensor or thermal-management codes.
- 2.Verify the ACTUAL coolant temperature with a scan tool data stream or infrared thermometer before trusting the dash reading.
- 3.Load-test the battery and verify charging voltage and the module's grounds.
- 4.Inspect the module and coolant temperature sensor connectors for corrosion, looseness, and coolant/water intrusion.
- 5.Check bus wiring to the module for chafing and damage.
- 6.Confirm whether the module was recently replaced or updated — a missing configuration is a common cause of invalid data.
- 7.If the module and its inputs check out, suspect an internal module fault and verify with manufacturer service data.
Repair cost
$90 – $800
Cost depends on the cause. Repairing a connector, ground, or wiring fault is often $90-$350. A failing coolant temperature sensor feeding the module bad data typically runs $80-$250 installed. Reprogramming or configuring the module after a replacement is usually $100-$300. Coolant temperature control module replacement with programming is the higher end at roughly $350-$800. Confirm the real coolant temperature first so you don't chase a wiring problem when the engine is actually overheating, or vice versa.
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
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.