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Home / DTC / U0630 — Lost Communication With Engine Coolant Temperature Sensor 4

U0630 — Lost Communication With Engine Coolant Temperature Sensor 4

Detailed page for trouble code U0630.

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Code

U0630

Generic U — Network/User

Lost Communication With Engine Coolant Temperature Sensor 4

Brand: Generic
Type: U — Network/User
Views: UK: 18 EN: 29 RU: 14
AI status
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Page language: EN

Causes

  • Open or short in ECT sensor 4 wiring or connector
  • Corroded or loose connector/pin at the sensor or module
  • Failed ECT sensor 4 (internal open/short)
  • Loss of reference voltage or ground for the sensor
  • CAN/LIN bus or module communication fault (ECM/BCM/module not transmitting)
  • Intermittent wiring damage (chafing, water intrusion)

Symptoms

  • Malfunction Indicator Lamp (MIL) or network warning illuminated
  • Engine coolant temperature PID for sensor 4 missing or shows erratic/invalid values on a scan tool
  • Cooling fan, gauge, or climate control behavior incorrect or inoperative (dependent on vehicle design)
  • Possible reduced engine performance or extended open-loop operation if PCM relies on that input
  • Intermittent faults or multiple related communication codes

What to check

  • Use a capable scan tool to read U0630 and any related codes; note freeze-frame and live data
  • Verify presence/absence of ECT sensor 4 PID/value with the scan tool (is data shown or reported ‘not available’?)
  • Inspect sensor 4 connector and wiring for corrosion, bent pins, damage, or moisture
  • Check for other U-codes indicating broader bus problems (U0100, U0073, etc.)
  • Verify vehicle history: recent repairs, aftermarket modules, or water damage near sensor harness
  • Check fuses and module power/ground circuits related to the sensor and its control module(s)

Signal parameters

  • Sensor type: typically a thermistor (NTC) whose resistance varies with temperature
  • Reference supply: module-provided reference (commonly 5 V) — verify presence with key ON (exact value vehicle-specific)
  • Signal voltage: typically varies between ~0.1–4.9 V depending on temperature and wiring (vehicle-specific)
  • Resistance: varies with temperature (higher ohms at low temps, lower ohms at high temps); exact ohm ranges are manufacturer-specific

Diagnostic algorithm

  1. Record codes and freeze-frame data; check for multiple communication codes that indicate bus issues.
  2. Attempt to view ECT sensor 4 PID with a scan tool. If PID is not present, confirm which module is expected to supply it (ECM, BCM, etc.).
  3. Visually inspect sensor 4 and its connector for damage, corrosion, or water intrusion; repair or clean as needed.
  4. With key ON (engine off), backprobe the sensor connector: verify reference voltage (usually ~5 V) and ground presence. Do not short pins. If reference or ground missing, trace to supplying module/fuse.
  5. Measure signal voltage while varying coolant temperature (or warming sensor area) or compare to another known-good ECT reading. Look for expected change in voltage. If signal stuck or open, suspect sensor or harness.
  6. Check continuity between sensor connector and the control module pin; repair any opens or high-resistance splices.
  7. Inspect CAN/LIN bus voltages and terminations if the system uses a networked sensor gateway. Look for bus-off conditions or other modules reporting comms loss.
  8. If wiring and voltages are good but no data is transmitted, replace the ECT sensor 4. Clear codes and test drive to confirm.
  9. If fault returns and wiring and sensor verified good, consider module-level failure or software; consult manufacturer service information for module reprogramming or replacement guidance.

Likely causes

  • Damaged/loose connector or wiring to ECT sensor 4
  • Failed ECT sensor 4 element (open/short or out-of-range)
  • Loss of reference voltage or ground at the sensor circuit
  • CAN/LIN bus or control module not transmitting sensor data

Fault status

⚠️ Status
Lost communication with Engine Coolant Temperature Sensor 4 — module is not receiving valid data from sensor 4 (data missing, out of range, or not transmitted).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

U0100 U0073 U0121 P0115 P0117 P0118
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