P0191 High Rationality Test

WARNING: This page is about a different car, the 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The engine speed is greater than 25 RPM for greater than 30 s.
The engine block heater is not active.
The engine coolant temperature (ECT), at shut down, is warmer than 72°C (161.6°F).
The ECT, at start-up, is colder than 54.8°C (130.6°F).
At start-up, if the ECT is warmer than the intake air temperature (IAT), the difference must be colder than 35°C (95°F).
At start-up, if the IAT is warmer than the ECT, the difference must be colder than 10°C (50°F).
The engine OFF time during soak is greater than 4 hours 27 min.
DTC P0191 runs the high rationality test during engine start only.