Code
U0699
Generic
U — Network/User
Lost Communication with Coolant Pump “F”
Views:
UK: 12
EN: 22
RU: 18
AI status
Completed
Completed
100%
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
- Read and record all stored DTCs and freeze frame data from all modules. Note occurrence conditions.
- Clear codes. Attempt to communicate with coolant pump F using scan tool; see if code returns.
- Verify battery and charging system voltage. Low voltage can cause modules to drop off network.
- Visually inspect connectors, pins and harness to coolant pump F. Repair any corrosion or damage.
- With key on and engine off, check for proper power and ground at the pump module connector (measure 12V and ground continuity).
- Inspect/replace any related fuses or relays. Re-test communication after replacement.
- Check CAN/LIN bus continuity and resistance. Measure CANH/CANL voltages at several nodes; compare to specification.
- Perform wiggle test and watch for intermittent communication while moving harness/connector.
- If wiring, power and bus look good but no communication, attempt reprogramming or re-flash per manufacturer instructions if available.
- If module still does not communicate and all vehicle-side checks are good, replace coolant pump module and verify repair.
- 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
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email