Downstream O2 Monitor

Perform the following:

• Ensure engine is at normal operating temperature, above 170°F.
• Decel Fuel Shut-off is Active.
• Minimum Engine RPM = 1600 RPM.
• Upstream O2S is less than .471 volts.

The PCM begins the Downstream O2S rationality test. The PCM looks at the Downstream O2S volts for 5 seconds, if less than .295 volts, the test passes. If the Downstream O2S is greater than .295 volts, the test increments a count of 1 and the test is done again. A count of 3 will set a DTC and store Freeze Frame Data.