P1153

CIRCUIT DESCRIPTION
The VCM supplies a reference voltage of approximately 0.45 volts (450 mV) to the Heated Oxygen sensor (HO2S) on the HO2S High signal circuit. When the Heated Oxygen sensor is cold, less than 200°C (392°F), the Heated Oxygen sensor signal voltage will read around 0.45 volts, and the VCM will keep the system in an Open Loop operation. When the Heated Oxygen sensor is warm, above 200°C (392°F), the Heated Oxygen sensor will swing from rich to lean rapidly, at least 1 swing every 2 seconds, if the VCM is in good control of the air fuel mixture. This DTC is designed so that if the Oxygen sensor is slow to respond to changes in exhaust oxygen content, then this DTC will set.

NOTE: If this voltage is measured using a 10 megaohm digital voltmeter, the voltage may read as low as 0.32 volts. The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1.0 volt (1000 mV) if the exhaust is rich to as low as 0.10 volt (10 mV) if the exhaust is lean.

When the HO2S temperature is below 360°C (600°F), the sensor will not produce any voltage and will behave like an open circuit. This will result in an Open Loop operation.

The HO2S heater provides for faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during a long extended idle. This DTC is a type B DTC.

CONDITIONS FOR SETTING THE DTC
The following conditions sets the DTC:

^ No fuel trim DTCs.
^ No TP sensor DTCs.
^ No Evaporative Emissions (EVAP) DTCs.
^ No IAT sensor DTCs.
^ No MAP DTCs.
^ No EGR DTCs.
^ No ECT sensor DTCs.
^ The DTC P0155 not set.
^ Closed Loop.
^ HO2S voltage between 0.300 volts and 0.600 volts.
^ Throttle position is greater than 10% but less than 20%.
^ L/R switches less than 50.
^ R/L switches less than 50.

ACTION TAKEN WHEN THE DTC SETS
The VCM turns on the MIL (Malfunction Indicator Lamp) when the diagnostic runs and fails.

The VCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records store this information.

CONDITIONS FOR CLEARING THE MIL/DTC
The VCM turns the MIL off after 3 consecutive drive trips that the diagnostic runs and does not fail.

A Last Test Failed (current) DTC clears when the diagnostic runs and does not fail.

A History DTC clears after 40 consecutive warm-up cycles with no failures of any emission related diagnostic test.

The VCM battery voltage is interrupted. The scan tool Clear Info function is used.

DIAGNOSTIC AIDS
Never solder the HO2S wires. For a proper wire and connector repair refer to wiring Repairs.

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.

2. This step checks to see if the other causes of this DTC have already been diagnosed.
3. Diagnose other DTCs first because they may have set this DTC.
4. With the engine running warm, coolant at least 85°C (185°F) and at fast idle, the HO2S voltage should rapidly swing above 0.60 volts and below 0.30 volts.
6. This step checks to see if the Oxygen sensor voltage is swinging between rich and lean very slowly or not at all.
9. This step checks for causes of the HO2S failure. If the sensor is replaced without finding the cause of the contamination, the replacement sensor may become contaminated.