Oxygen Sensor and Fuel System Monitoring Description

[Joey]

1. Fault Codes:
P0130 Oxygen Sensor Circuit Malfunction (Period) AUL
P0131 Oxygen Sensor low voltage Bank 1 Sensor 1
P0132 Oxygen Sensor high voltage Bank 1 Sensor 1
P0133 Oxygen Sensor Response Rate fault Bank 1 Sensor 1
P0136 Oxygen Sensor Circuit Malfunction (Period) ADL
P0137 Oxygen Sensor low voltage Bank 1 Sensor 2
P0138 Oxygen Sensor high voltage Bank 1 Sensor 2
P0150 Oxygen Sensor Circuit Malfunction (Period) BUL
P0151 Oxygen Sensor low voltage Bank 2 Sensor 1
P0152 Oxygen Sensor high voltage Bank 2 Sensor 1
P0153 Oxygen Sensor Response Rate fault Bank 2 Sensor 1
P0156 Oxygen Sensor Circuit Malfunction (Period) BDL
P0157 Oxygen Sensor low voltage Bank 2 Sensor 2
P0158 Oxygen Sensor high voltage Bank 2 Sensor 2
P0171 System too lean, Bank 1
P0172 System too rich, Bank 1
P0174 System too lean, Bank 2
P0175 System too rich, Bank 2
P1137 Oxygen Sensor indicates lean fault - Bank 1
P1137 Oxygen Sensor High MSR Fault Bank 1
P1138 Oxygen Sensor indicates rich fault - Bank 1
P1138 Oxygen Sensor Low MSR Fault Bank 1
P1157 Oxygen Sensor indicates lean fault - Bank 2
P1157 Oxygen Sensor High MSR Fault Bank 2
P1158 Oxygen Sensor indicates rich fault - Bank 2
P1158 Oxygen Sensor Low MSR Fault Bank 2
P1171 Lean Fuelling Fault
P1172 Rich Fuelling Fault
P1176 Long term fuel trim too lean, banks 1&2 (FMFR)
P1177 Long term fuel trim too rich, banks 1&2 (FMFR)
P1178 Long term fuel trim too lean, banks 1&2 (AMFR)
P1179 Long term fuel trim too rich, banks 1&2 (AMFR)
2. Monitoring Procedure
Summary
The oxygen sensors are tested as the first stage in a suspected fuel system fault. There are further periodic tests on the response rates of the sensors. These are compared against reference rates. If the measured response rate is lower than the reference then the test will fail. The output voltage is range checked. If these tests are not passed then the appropriate fault count will be incremented; otherwise it will decrement to zero. If the count reaches a given threshold then a fault is present.

Integrator clamp tests will also be performed on the control sensors. If any of the fuelling feedback integrators reach their clamp values, then a fuelling change followed by additional smaller fuelling changes (if required) will be introduced up to a maximum fuelling change limit, to try and move the integrator off its clamp value. If this is successful then a fuelling fault is suspected and the fuelling system diagnostics are performed. If it is not successful and the sensor passed the range test above, then an indeterminate (failed to switch) fault is present. The fuelling system diagnostics can diagnose a number of faults depending on the state of the feedback integrators.



Range Check
The output voltage of each fitted sensor is monitored to check that it is within range. If the output voltage is less than a calibrated minimum voltage or greater than maximum voltage then an appropriate fault counter will be incremented. If the voltage is in range then the counter is decremented to zero. If the counter reaches a predetermined limit then a range fault is present; the fault will remain present until the counter reaches zero.
Response Rate Measurements
The response rates of the controlling oxygen sensors are measured. This measurement will take place during the normal sensor switching, which occurs in closed loop control. If either of the response times in the Lean to Rich direction or the Rich to Lean direction are greater than their respective maximum limits, then the appropriate response rate fault counter will be incremented; the counters will be decrement to zero if the appropriate response time is less than its limit. If either counter reaches its maximum value then the appropriate response rate fault is present. The fault will remain present until the counter reaches zero.
Mark Space Ratio Measurements
The Mark/Space Ratio (MSR) of the controlling oxygen sensors is calculated to give an indication of the Dynamic Lambda to which the engine management system is controlling. The Oxygen Sensor Measured Mark Space Ratio value is calculated within the ECM's Oxygen Sensor Signal Measurement strategy and then averaged over a number of iterations of this strategy.

If the average value is not within the required limits then a fault counter pertaining to Mark Space Ratio faults will be incremented; otherwise it will be decrement until zero. The limits will be of a minimum MSR and Maximum MSR. These limits will be mapped against engine speed and load. If the counter reaches a predetermined limit then a Mark Space Ratio fault is present; the fault will remain present until the counter reaches zero.



Switching Period Measurements
If the oxygen sensor period is greater than Oxy_Sens_Diag_Max_Period_C then a fault counter Oxy_Sens_Diag_Period_Faults [A, B] will be incremented every time Lambda Feedback switches {for the bank in question}. If the period is within the range then the fault counter is decremented to zero. If the counter reaches the value Oxy_Sens_Diag_Fault_Limit_C, then a fault will remain present until the counter reaches zero.
Oxygen Sensor Clamp Tests
If the integrator is on the enleanment clamp with purge disabled then the fuelling is reduced by an amount Oxy_Sens_Diag_Enlean_Percent and the system waits for a period Oxy_Sens_Diag_Clamp_Test_Time. If the integrator does not move off the clamp then the fuelling is reduced by Oxy_Sens_Diag_L_Extra_Percent amount and the system again waits for a period Oxy_Sens_Diag_Clamp_Test_Time. This will be repeated until the integrator moves off clamp or the fuelling has reached a maximum permitted fuelling change. If the fuelling change(s) caused the integrator to move off clamp then a fuelling fault is suspected and further fuel system diagnostics will be performed; if not then an Oxygen Sensor Failed to Switch Lean fault is present. All fuelling changes will be removed at this time.

If the integrator is on the enrichment clamp then the fuelling is increased by an amount Oxy_Sens_Diag_Enrich_Percent and the system waits for a period Oxy_Sens_Diag_Clamp_Test_Time. If the integrator does not move off the clamp then the fuelling is increased by Oxy_Sens_Diag_R_Extra_Percent amount and the system again waits for a period Oxy_Sens_Diag_Clamp_Test_Time. This will be repeated until the integrator moves off clamp or the fuelling has reached a maximum permitted fuelling change. If the fuelling change(s) caused the integrator to move off clamp then a fuelling fault is suspected and further system diagnostics will be performed; if not then an Oxygen Sensor Failed to Switch Rich fault is present. All fuelling changes will be removed at this time.



Note: Each banks clamp test is considered to be a single intrusive test, only one test can be active at a time, with initial priority given to bank 1.
Fuelling System Clamp Tests
All diagnostic fuelling changes will be removed before performing the tests below. If an integrator returns to its clamp within a time designated Oxy_Sens_Diag_Clamp_Delay then the conditions below will be applied. If this is not the case then this test is abandoned until again triggered by the oxygen sensor diagnostics.

While a bank is on clamp, an appropriate fault counter for each bank will be incremented. If the bank moves off clamp then the counter will decrement until zero. An integrator clamp test for bank A or B is considered to be complete if the fault counter reaches zero or the fault limit. If the value of the fault counter reaches its limit value a clamp fault is present; the fault will remain present until the counter reaches zero. All clamp faults for that bank will be cleared when the counter reaches zero. When a clamp fault is present the conditions below will be applied to determine which fault is present.



One integrator is at the maximum enrichment clamp and the other not at the maximum enrichment clamp; a Reduced Fuel Flow Fault is present for the appropriate bank.
Both integrators are on the maximum enrichment clamp; a Lean Fuelling Fault is present. This diagnostic will be disabled if the fuel level is less than the permissible fuel level for the diagnostic.
One integrator is at the maximum enleanment clamp and the other is not at the maximum enleanment clamp; an Excess Fuel Flow Fault is present for the appropriate bank.
Both integrators are on the maximum enleanment clamp; a Rich Fuelling Fault is present.
Long Term Fuel Trim Diagnostics
These tests monitor the performance of the Adaptive Fuelling System. If the corrections it applies exceed limits, then the appropriate fault is present. The fault remains until the system returns to within limits.
The checks performed are detailed below.

If the ADAP_FMFR_CORR value is greater than FUEL_DIAG_MAX_POS_FMFR_CORR then a MAX_POSITIVE_FMFR_CORR_FAULT is present.
If the ADAP_FMFR_CORR value is less than FUEL_DIAG_MAX_NEG_FMFR_CORR then a MAX_NEG_FMFR_CORR_FAULT is present.
If the ADAP_AMFR_CORR value is greater than FUEL_DIAG_MAX_POS_AMFR_CORR then a MAX_POSITIVE_AMFR_CORR_FAULT is present.
If the ADAP_AMFR_CORR value is less than FUEL_DIAG_MAX_NEG_AMFR_CORR then a MAX_NEGATIVE_AMFR_CORR_FAULT is present.



3. Primary Detection Parameter
Range Check

Oxygen Sensor Voltage - See circuit for sensor appended.
Response Rate Measurements
The rise and fall times of the oxygen sensor output signal between two voltage levels.
Mark/Space Ratio Calculations
The calculated ratio for each state that the output signal will attain during normal closed loop fuelling.
Switching Period Measurements
The measured time for a sensor to complete a full switching cycle.
Oxygen Sensor Clamp Tests
The output of an integration equation, normally observed as percentage enrichment or enleanment of fuelling - short-term fuel trim.
Fuelling System Clamp Tests
An integrator swing from the clamp within a time, defined by the fault counter operation speed.
Long Term Fuel Trim Tests.
Adaptive Fuel Mass Flow rate Correction


4. Fault Criteria Limits
Range Check
Oxygen Sensor Minimum Voltage 0.015 V
Oxygen Sensor Maximum Voltage 4.98 V

Response Rate Measurements


Oxygen Sensor Maximum Rich to Lean Time 0.235 seconds
Oxygen Sensor Maximum Lean to Rich Time 0.349 seconds

Mark/Space Ratio Calculations


Oxygen Sensor Minimum MSR - An 8 x 8 map of speed and load sites - values from 0 to 13.7
Oxygen Sensor Maximum MSR - An 8 x 8 map of speed and load sites - values from 25.4 to 39.1

Switching Period measurements


Maximum oxygen sensor switching period 1.2 seconds

Oxygen Sensor Clamp Tests


Oxygen Sensor clamp test time 7 secs

Fuelling System Clamp Tests.


Fault counter limit 20 secs

Long Term Fuel Trim Tests.


FUEL_DIAG_MAX_POS_FMFR_CORR +0.62 g/s (injector fuel flow rate)
FUEL_DIAG_MAX_NEG_FMFR_CORR -0.62 g/s (injector fuel flow rate)
FUEL_DIAG_MAX_POS_AMFR_CORR +5.48 kg/hr (air mass flow rate)
FUEL_DIAG_MAX_NEG_AMFR_CORR -5.48 kg/hr (air mass flow rate)
5. Monitoring Conditions

Oxygen Sensor Diagnostics will only run when the Engine Stabilized [i.e.-internally calculated value] flag is set; and closed loop fuelling is active. If this is not the case then all fault counts will be suspended but not cleared; any clamp tests, which are in progress, will be aborted
Oxygen Sensor Period Diagnostics will only run when the Local Engine Stabilized Flag is set. This is a Global Engine Stabilized based off unsigned delta air per stroke. This Local Flag activates when the driver oscillates the throttle.
All tests will be abandoned if the oxygen sensor heater diagnostics report a fault with the heater for the sensor in question, or the heater control algorithm is inactive.
Response rate tests will not run when fuelling feedback is on clamp or when a fault has been detected which affects fuelling feedback control (i.e. misfire, injector failure or coil failure).
Clamp tests will only run above a coolant temperature threshold and a throttle position threshold. Clamp tests will be disabled if: A misfire fault has been detected on that bank An injector fault has been detected on that bank An ignition coil fault has been detected An Oxygen Sensor signal is out of range (on that sensor) An Oxygen Sensor response rate fault has been detected (on that sensor) An air meter fault has been detected during the current journey A throttle potentiometer fault has been detected
Fuel system clamp tests will be disabled when Oxygen sensor clamp tests are disabled or when fuelling feedback control is not using the normal Oxygen sensor.
While oxygen or fuel system clamp tests are running on one bank then clamp tests on the other bank cannot be stored.
When clamp test have been completed on either bank, they will not be repeated for the remainder of that trip.
The response rate and switching period diagnostics are only performed when the Air Mass Flow rate exceeds a predetermined minimum, otherwise all fault counters are frozen.
6. Monitoring Time Length / Frequency of Checks
The frequency of the oxygen sensor and fuel system diagnostic is 10Hz .
7. Criteria for Storing Fault Codes
If the Oxygen Sensor and Fuel System Diagnostic indicates a failure, then a set of conditions are stored. A fault code will be stored if a failure is detected on a subsequent driving cycle while the conditions are still stored. The conditions can be erased on intervening fault free driving cycles as allowed in OBD II regulations.
8. Criteria for Illuminating MIL
If the Oxygen Sensor and Fuel System Diagnostic indicates a failure, then a set of conditions are stored. The MIL will be illuminated if a failure is detected on a subsequent driving cycle while the conditions are still stored. The conditions can be erased on intervening fault free driving cycles as allowed in OBD II regulations.
9. Criteria for Determining Out of Range Input Signals
The Oxygen Sensor is subject to low and high voltage limits of 0.015V & 4.98V respectively as above.