P0030

CIRCUIT DESCRIPTION
Heated oxygen sensors (HO2S) are used to minimize the amount of time required to enter Closed Loop fuel control operation and to allow accurate catalyst monitoring. The HO2S 1 heater is fed power directly from ignition 1. The HO2S 1 heater control circuit or heater ground is connected to the Powertrain Control Module (PCM). The PCM controls HO2S heater operation by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. The driver for the HO2S 1 heater control circuit has the ability to measure the amount of current drawn by the controlled device.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
The PCM detects that the heater control circuit current is outside a calibrated range.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the MIL OFF after 3 consecutive drive trips during which the diagnostic runs and passes.
^ A last test failed, or the current DTC, clears when the diagnostic runs and passes.
^ A History DTC clears after 40 consecutive warm-up cycles, it no other emission related diagnostic failures are reported.
^ Use a scan tool in order to clear the MIL diagnostic trouble code.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) Description, Clearing Diagnostic Trouble Codes.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter Kit J 35616-A Notice in Service Precautions

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help to determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

If the problem is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

steps 1-3:

steps 4-15:

The numbers below refer to the step numbers on the diagnostic table.
2. Check the HO2S heater current with the engine at operating temperature, and allow time for the heater current to stabilize. The HO2S heater current is initially higher until the sensor reaches the full operating temperature.
4. Ensures that the ignition 1 voltage circuit to the HO2S is not open or shorted. The test lamp should be connected to a good chassis ground in case the HO2S low reference or HO2S heater low control circuit is malfunctioning.
5. Checks the HO2S heater low control circuit. The engine must be running for the PCM to enable the heater.
6. Checks for a short to voltage in the HO2S heater control circuit.