Home / DTC / U0699 — Lost Communication with Coolant Pump “F”

U0699 — Lost Communication with Coolant Pump “F”

Detailed page for trouble code U0699.

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Code

U0699

Generic U — Network/User

Lost Communication with Coolant Pump “F”

Views: UK: 12 EN: 22 RU: 18
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Page language: EN

Causes

  • Failed coolant pump control or monitoring module
  • Open or shorted wiring between the pump module and network or power/ground
  • Corroded or loose connector at the pump module or harness
  • Blown fuse or failed relay supplying the pump/module
  • Fault on the vehicle communication bus (CAN/LIN) such as missing termination or damaged wiring
  • Software or module internal fault (module hung or corrupted)

Symptoms

  • Stored U0699 (and possibly other U-codes) in one or more modules
  • Coolant pump F may not run or run intermittently
  • Poor coolant circulation, engine running hot or temperature regulation issues
  • Illumination of warning lamp(s) related to emission or powertrain (depends on vehicle)
  • Reduced cooling performance or vehicle limp-home mode in some systems
  • No response from coolant pump F when commanded by a scan tool

What to check

  • Scan all modules; record U0699 and any other related U- or P-codes and freeze frame data
  • Check battery voltage and charging system; ensure 12V supply is stable
  • Inspect connectors and wiring at coolant pump F for corrosion, damage, or loose pins
  • Verify fuse(s) and relay(s) feeding the pump/module
  • Attempt communication with the pump module using a capable scan tool
  • Check CAN/LIN bus health: measure bus voltages, verify termination resistance, and look for shorts to power/ground

Signal parameters

  • Module supply voltage: nominal 11–14 V when key on/run
  • Ground: low resistance to chassis (typically
  • CAN bus idle voltages: CANH ≈ 2.5 V, CANL ≈ 2.5 V (recessive); dominant CANH ≈ 3.5 V, CANL ≈ 1.5 V
  • CAN bus differential voltage when active: typically ~2.0 V
  • Expected termination resistance: about 60 Ω total (two 120 Ω resistors in parallel on most vehicles)
  • Message frequency/IDs: coolant pump status/control frames vary by manufacturer (verify ID and expected rate with service data)

Diagnostic algorithm

  1. Read and record all stored DTCs and freeze frame data from all modules. Note occurrence conditions.
  2. Clear codes. Attempt to communicate with coolant pump F using scan tool; see if code returns.
  3. Verify battery and charging system voltage. Low voltage can cause modules to drop off network.
  4. Visually inspect connectors, pins and harness to coolant pump F. Repair any corrosion or damage.
  5. With key on and engine off, check for proper power and ground at the pump module connector (measure 12V and ground continuity).
  6. Inspect/replace any related fuses or relays. Re-test communication after replacement.
  7. Check CAN/LIN bus continuity and resistance. Measure CANH/CANL voltages at several nodes; compare to specification.
  8. Perform wiggle test and watch for intermittent communication while moving harness/connector.
  9. If wiring, power and bus look good but no communication, attempt reprogramming or re-flash per manufacturer instructions if available.
  10. If module still does not communicate and all vehicle-side checks are good, replace coolant pump module and verify repair.
  11. After repairs, clear codes and perform road/test and re-scan to confirm U0699 does not return.

Likely causes

  • Damaged or disconnected connector at the coolant pump module
  • Faulty power or ground to the pump module (blown fuse, poor ground)
  • CAN/LIN wiring open, shorted, or high resistance between module and network
  • Corroded pins causing intermittent communication
  • Module failure (most likely if wiring and power check good)

Fault status

⚠️ Status
Lost Communication with Coolant Pump "F" — the coolant pump module is not responding on the vehicle communication network.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
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