Cause
Failed manifold tuning solenoid
The solenoid that operates the manifold tuning valve, failed so the valve is never commanded. It is the control half of the same system whose mechanical half seizes, and separating the two is the whole diagnosis — the codes name the valve's performance either way.
On vacuum-operated systems the solenoid switches vacuum rather than moving the valve directly, which adds two more failure points: the vacuum supply and the lines. A solenoid that clicks correctly while the valve does not move means vacuum is not reaching the actuator, not that the solenoid is faulty.
So test in order: does the solenoid switch, does vacuum reach the actuator, does the actuator move the valve. Each step is quick and each eliminates a different part. Electric solenoids fail as an open winding, which the module reports as a circuit fault — measure the resistance at the connector, which distinguishes a failed coil from a harness fault immediately.
Typically a moderate job.
Codes this can cause (2)
Codes where this is a likely explanation first, rather than merely a possible one.
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