P0161
CIRCUIT DESCRIPTION
The PCM supplies a bias voltage (approximately 450 mV) on the Heated Oxygen Sensor (HO2S) signal high and low circuits. When the ignition is turned to the ON position, battery voltage is supplied to the HO2S heater. As the heater reaches operating temperature, the HO2S voltage responds by changing from a bias voltage range to normal operation. Typically, as the HO2S reaches operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, it is possible for the HO2S voltage to go above 450 mV.
The PCM will run the heater test only on a cold start (depends on cumulative air flow) and only once an ignition cycle. When the engine is started the PCM will monitor the HO2S voltage. When the HO2S
voltage goes above or below the bias range threshold, the PCM will determine how much time it took. If the PCM detects that it took too much time for the HO2S to enter into normal operating range, a DTC will set. The time it takes the HO2S to reach operating temperature is based on the amount of air that flows into the engine.
CONDITIONS FOR SETTING THE DTC
DTCs P0100, P0102, P0103, P0112, P0113, P0117, P0118, P0125, P0122, P0123, P0157, P0158, P0160, P0200 not set.
Engine is started and Intake Air and Engine Coolant temperatures are less than 50°C (l22°F) and are within 3°C (5°F) of each other at start-up.
Ignition voltage between 10 volts and 16 volts.
Engine air flow less than 40 grams per second.
TP sensor angle less than 20%.
HO2S voltage remains between 300 mV and 700 mV for a predetermined amount of time (depends on engine coolant temperature and air flow).
ACTION TAKEN WHEN THE DTC SETS
The PCM will illuminate the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.
The PCM will record operating conditions at the time the diagnostic fails. The first time the diagnostic fails, this information will be stored in Failure Records. If the diagnostic reports a failure on the second consecutive drive trip, the operating conditions at the time of failure will be written to Freeze Frame and the Failure record will be updated.
CONDITIONS FOR CLEARING THE MIL/DTC
The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
A last test failed (Current DTC) will clear when the ignition is cycled and the diagnostic runs and does not fail.
A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
PCM battery voltage is interrupted.
Using a Scan tool.
DIAGNOSTIC AIDS
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail.
Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.
The heater diagnostic will only run on a cold start and it will only run once per ignition cycle.
An oxygen supply inside the HO2S is necessary for proper operation. This supply of oxygen is provided through the HO2S wires. All HO2S wires and connections should be inspected for breaks or contamination.
For intermittents, refer to Symptoms. See: Testing and Inspection
TEST DESCRIPTION
Number(s) below refer to step numbers on the diagnostic table.
The engine must be allowed to cool, as the HO2S maybe at operating temperature and no drop or rise in HO2S voltage would occur. If the HO2S voltage stays between 300-700 mV indicates the HO2S heater is inoperative. For any test that requires probing the PCM or a component harness connector, must use the Connector Test Adapter kit J 35616-A. Using this kit will prevent damage to the harness connector terminals.
If more then one HO2S DTC is set, is good indication that the HO2S fuse is open. Check all related circuits going to all heated oxygen sensors for a short to ground. If all wiring checks to be OK, it may be necessary to disconnect each HO2S one at a time to locate a shorted sensor.
It may be necessary to lower the exhaust system to gain sufficient access to an HO2S and/or it's connector. Refer to Exhaust System Checks whether B+ supply is available at the sensor
Checks whether a ground is available at the sensor.
Checks whether the HO2S heater element is internally open.
P1441
CIRCUIT DESCRIPTION
The EVAP vacuum switch is a normally closed switch connected to ground, mounted in the vacuum line between the EVAP canister and the EVAP solenoid. 12 volts is supplied to the switch through a pull-up resistor in the PCM. When the PCM commands the EVAP canister purge solenoid valve open (purge ON) and engine vacuum draws the evaporative emissions from the canister, the EVAP vacuum switch opens (signal voltage high) providing feedback to the PCM that the EVAP system is operating. When the PCM commands purge OFF, the EVAP vacuum switch closes (signal voltage low) confirming purging has ceased.
CONDITIONS FOR SETTING THE DTC
DTCs P0100, P0101, P0102, P0103, P0106, P0323, P0325, P0327, P0332, P0335, P0336, P0372, P0400, P0403, P0410, P0412, P0420, P0430,P0441, P0443, P0500, P0502, P0503, P0506, P0507, P0530, P0531, P071 9, P0758, P1415, P1642, P1652 not set.
ECT less than 115°C (239°F)
IAT greater than 3°C (37°F)
Engine speed between 500 and 3000 RPM
TP Angle less than 50%
MAP less than 70 kPa
BARO greater than 77 kPa
Purge not enabled
The PCM detects high signal voltage on the EVAP vacuum switch signal circuit when the PCM is not commanding purge ON.
Fault present for 5 seconds
ACTION TAKEN WHEN THE DTC SETS
The PCM will illuminate the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.
The PCM will record operating conditions at the time the diagnostic fails. The first time the diagnostic fails, this information will be stored in Failure Records. If the diagnostic reports a failure on the second consecutive drive trip, the operating conditions at the time of failure will be written to Freeze Frame and the Failure record will be updated.
CONDITIONS FOR CLEARING THE MIL/DTC
The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not tail.
A last test tailed (Current DTC) will clear when the diagnostic runs and does not tail.
A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
PCM battery voltage is interrupted.
Using a Scan tool.
DIAGNOSTIC AIDS
Before replacing any components, visually/physically check for the following:
Mis-routed harness.
Rubbed through wire insulation.
Broken wire inside the insulation.
Kinked or damaged vacuum hoses.
Physically damaged system components.
Inspect components and vacuum lines for traces of carbon or other contaminants. The presence of foreign material may be causing a restriction in the system or preventing the solenoid valve from closing properly. Either condition may cause a DTC to set.
For intermittents, refer to Symptoms. See: Testing and Inspection
TEST DESCRIPTION
Number(s) below refer to step numbers on the diagnostic table.
Since the vacuum switch only requires a vacuum of only a few inches of water to operate (a very small unit of vacuum), a properly operating switch will transition even with the canister end of the hose disconnected and un-plugged.