Circuit Description

Powertrain Control Module (PCM) runs heater test only after a cold start and only once during an ignition cycle. When engine is started, PCM monitors HO2S 1 voltage. When HO2S 1 voltage indicates a sufficiently active sensor, PCM looks at how much time has elapsed since start-up. If PCM determines that too much time was required for HO2S 1 to become active, DTC will set.

Conditions for setting this DTC are as follows:

• No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
• ECT and IAT is less than 95°F (35°C) at start-up.
• Average MAF for the sample period is less than 15 gm/s.
• HO2S 1 signal voltage remains within 150 mV of bias voltage (about 450 mV) for a longer amount of time than it should.