P0E78

Coolant Bypass Valve A Control Circuit Range/Performance

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–56 (est.)

Symptoms

Unstable engine operation
Increased engine temperature
Reduced interior heating efficiency
Check Engine light comes on
Possible misfires

Causes

Coolant bypass valve malfunction
Open or short circuit in control circuit
Poor contact in circuit connectors
Engine control unit (ECU) malfunction
Valve is dirty or clogged

How to Fix

Check the condition of the coolant bypass valve
Check the integrity of the control circuit and connectors
Check valve resistance and operation
If necessary, replace the valve or repair the circuit
Reset the error code and check if it returns

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