P2682: Engine Coolant Bypass Valve A Control Circuit Low
What to do
Expect slow warm-up, a cool-running engine and a weak heater. Not dangerous.
Ask for the connector and the thermostat housing to be checked for coolant leakage before the valve is replaced. This valve is mounted on or in the thermostat housing, surrounded by seals and hose joints, and on many engines that housing is plastic and goes porous with age. A slight weep drips coolant into the plug, and because coolant conducts and corrodes it causes a real electrical fault with nothing wrong with the wiring. If that is what has happened, the housing is the repair and the valve may be perfectly good.
As at P2681, do not let a thermostat be fitted on the assumption that slow warm-up must be one — on this engine the temperature is controlled electrically.
What this code means
The coolant bypass valve's control circuit reads below its valid range — a short to ground, or a module output that has failed low.
What the valve does, and why slow warm-up on these engines is not automatically a thermostat, is set out at P2681.
The coolant-in-the-connector mechanism described at P2679 applies here with particular force, because of where this valve is mounted. It is part of the thermostat housing or bolted directly to it — surrounded by hose joints, seals and, on many engines, a plastic housing that becomes porous with age. A housing that has begun to weep puts coolant straight onto its own connector, and the electrical fault that follows names the valve while the actual problem is a leaking housing that will need replacing anyway.
So the sequence to insist on is: look at the plug and the housing before the valve is condemned. If there is coolant in the connector, finding where it came from is the repair, and the valve may well be fine.
The driveability consequence is as at P2681 — a cool-running engine rather than an overheating one, in most designs.
Likely causes
Start here
- Coolant leak into the sensor connector · moderate
- Wiring shorted to ground · moderate
- Faulty engine coolant bypass valve · moderate
- Corroded or loose connector · easy
Less common
- Control module driver failure · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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