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swartlkk -> P0154 Explained (4/14/2008 6:47:34 PM)
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P0154 - HO2S Circuit Insufficient Activity Bank 2 Sensor 1
Schematic
[img]http://i11.photobucket.com/albums/a187/swartlkk/2000%20Bravada/th_P0155_SC.gif[/img]
CIRCUIT DESCRIPTION
The Heated Oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high, and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.
The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. It also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or "lean-out" the mixture, when the HO2S detects a rich exhaust condition.
Certain vehicle models utilize an oxygen sensor behind the catalytic converter in order to monitor catalyst efficiency.
This Diagnostic Trouble Code (DTC) determines if the HO2S is functioning properly. It checks for an adequate number of HO2S voltage transitions above and below the bias range of 300-600 mV . This DTC sets when the Vehicle Control Module (VCM) fails to detect a minimum number of voltage transitions above and below the bias range during the test period. Possible causes of this DTC are:
* An open or a short to voltage on either the HO2S signal or HO2S low circuits
* A malfunctioning HO2S
* A problem in the HO2S heater or its circuit
* A faulty HO2S ground
This DTC determines if the HO2S is functioning properly by checking for an adequate number of HO2S voltage transitions above and below the bias range of 300-600 mV . This DTC sets when the VCM fails to detect a minimum number of voltage transitions above and below the bias range during the test period. Possible causes of this DTC are listed below.
* An open circuit or a short to voltage on either the HO2S signal or HO2S low circuits
* A malfunctioning HO2S
* A problem in the HO2S heater or its circuit
* A poor HO2S ground
CONDITIONS FOR RUNNING THE DTC
* No active TP sensor DTCs
* No active EVAP system DTCs
* No active IAT sensor DTCs
* No active MAP sensor DTCs
* No active ECT sensor DTCs
* No active MAF sensor DTCs
* No active misfire DTCs
* No intrusive test in progress
* No device controls active
* The system voltage is between 11.7-17 volts .
* The engine has been running for more than 2 minutes .
O2 Temperature Test:
* The Decel Fuel Cutoff Mode (DFCO) is not active.
* The ECT is more than 58.5°C (137°F) .
* The MAF is more than 13 g/s .
O2 Sensor Open Test Enable:
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