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U0617 Lost Communication With Engine Coolant Bypass Valve C

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Unlike its LIN-based neighbours, GM uses U0617 for a coolant bypass valve whose position sensor transmits SENT frames (SAE J2716) to the engine controller. The tables 25OBDG03B and 25OBDG04B count a failure when the input hardware flags a message fault, when pulses arrive but the newest frame is older than 6.25 ms, or when the SENT pin voltage stays above or below a controller limit while frames go stale. Four failures within a five-second window set the code as Type B over two trips; the 2019 table 19OBDG03D still ran it as Type A after one trip. Suppliers such as Rheinmetall offer coolant valves with SENT position feedback. Typical causes are wiring and connector faults on the three-wire sensor line. The valve may stop being regulated, so warm-up and heater output can suffer.

Likely causes

SENT signal, 5 V supply or ground wire of the valve position sensor open or shorted
Corroded or loose connector at the valve
Position sensor inside the valve failed (usually replaced with the valve)
SENT input of the engine controller faulty

Symptoms

  • Check engine light (on GM after two trips, on 2019 calibrations after one)
  • Slow warm-up or reduced heater output
  • Possibly further coolant valve codes stored at the same time

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–700
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant bypass valve csensor wiring

Related codes

U0615U0616U0618U063FP0128

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, rheinmetall.com.