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Tim's Auto Repair
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i have a code p0141 o2sensor heater circuit malfuction ( bank1-sensor2)

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i have a code p0141 o2sensor heater circuit malfuction ( bank1-sensor2) the car is a 1997 cavalier 2.4ohc it has 2 sensor but i dont know which one is sensor2.

hi

have you replaced the #2 02sensor?

Customer: replied 6 years ago.
no i would like to know which one is the #2 sensor

this is the one at the rear of the catalyst converter..not the one closest to the engine....first,you may want to check the wiring to the sensor,,it may be damaged

thanks

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P0141

CIRCUIT DESCRIPTION
In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The Powertrain Control Module (PCM) has the capability to monitor this process by using a rear Heated Oxygen Sensor (HO2S) 2. The HO2S 2, located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalysts ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front Oxygen Sensor (O2S) 1.

Obstruction of the air reference and degraded HO2S 2 performance can result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

CONDITIONS FOR RUNNING THE DTC

  • The ignition 1 signal is greater than 10 volts.
  • The Engine Coolant Temperature (ECT) is less than 45°C (113°F).
  • The Intake Air Temperature (IAT) is less than 45°C (113°F).
  • The difference between the ECT and the IAT is less than 7°C (45°F).
  • The fuel level is more than 10 percent.
  • The rear O2 voltage is between 395-495 mV.

CONDITIONS FOR SETTING THE DTC

  • The HO2S voltage does not go greater than 600 mV or less than 300 mV within 110-255 seconds after cold start.
  • Average flow must be less than 20 g/s during the test time.

ACTION TAKEN WHEN THE DTC SETS

  • The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

  • The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
An intermittent could be the result of the following conditions:

  • A faulty electrical connection
  • Moisture in the connector/wiring
  • Rubbed-through wire insulation
  • A broken wire inside the insulation

Check for a faulty electrical connection, or for a damaged harness. Inspect the harness electrical connectors for the following conditions:

  • Improper mating
  • Broken locks
  • Improperly-formed electrical connectors
  • Damaged terminals
  • A faulty terminal-to-wire connection
  • A damaged harness

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

TEST DESCRIPTION

Steps 1-6
Steps 7-16
The numbers below refer to the step numbers on the diagnostic table.

 

  1. As the heater warms the oxygen sensor to operating temperature, the HO2S will output a voltage in relation to the amount of oxygen in the exhaust. With the ignition ON and the engine OFF, the exhaust usually contains a high oxygen content. With the engine OFF the HO2S voltage will usually decrease from the initial, or bias, voltage due to the high oxygen content.
  1. This step checks for proper HO2S heater ignition 1 voltage and ground supply.
  2. This step checks for proper PCM and signal circuit operation.
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