DTC P1570: Variable Tumble Control System Solenoid Valve Circuit, High Input: Condition

WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when PCM detects high voltage input from Variable Tumble Control System (VTCS) solenoid valve. Input voltage is monitored when:

Engine speed is less than 3250 RPM.
Engine coolant temperature is less than 149°F (65°C).
Throttle valve opening angle is less than 14 percent (A/T) or 12.5 percent (M/T) at 2500 RPM.
VTCS solenoid valve is on.

This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are:

Open circuit between VTCS solenoid valve and main relay.
Open or short circuit between VTCS solenoid valve and PCM.
PCM malfunction.
VTCS solenoid valve malfunction.