4.1.3 Drive Cycle Information
- Start engine and bring to normal operating temperature > 75 °C (167 °F).
- With the gear selector in Park or Neutral, hold the engine speed at 2500 RPM for 5 minutes.
- Drive vehicle ensuring that vehicle speed exceeds 15 km/h (10 mph) and the engine speed exceeds 1500 RPM.
- Stop the vehicle and check for any temporary DTCs.
Recording segment time and position, and its manipulation
The monitor records crank angle time data every 30° of rotation with a 250 nanosecond measurement accuracy. Each 30° period is known as a 'segment'. The starting point of the segments relative to TDC firing and the number of segments used can be defined for each application so as to give the best and most robust probability of misfire detection. To maintain good detection across the entire engine speed range the measurement period can be altered between low and high engine speeds. The engine speed, at which the measurement period is altered, if any, is determined by experiment.
Additionally, a third measurement period is defined for detection during start-up and when catalyst warm up ignition retard is being used after engine start.
The angular speed of the crankshaft during the ignition stroke is calculated using the segment data, multiplied by a scaling factor for easier storage in the ECM's memory, manipulated further and stored for each cylinder firing
Misfire 'signal' calculation
Where calculated adaption values have been stored in memory the adaptive signal will be calculated. This signal generally has the best opportunity to detect. However, the signal requires data in each speed breakpoint to interpolate between. If there is a breakpoint where no adaptions have been stored then the adaptive signal will only be used for misfire judgements up to the breakpoint immediately below it. For example if there is adaption data stored in memory up to 2000 RPM but none at 2500 RPM the adaptive signal will only be used up to 2000 RPM.
To support detection across the entire engine speed range further misfire 'signals' are calculated. These signals are not adjusted for errors in crank angle tolerance. These signals typically give good probability of detection at low engine speeds but become less effective at higher engine speeds.
Misfire judgement
Misfire judgements are delayed by one firing cycle. This is to allow comparison of the signal with the cylinders that fire before and after it, eliminating 'noisy' signals. Should the monitor repeatedly eliminate the signal over 5 consecutive firings on the same cylinder the monitor will assume that two adjacent cylinders are misfiring, ignore the signal check and allocate the 5 eliminated misfire judgements to the appropriate cylinder.
Adapted and un-adapted signals are compared to their respective thresholds in series. The diagram below illustrates the behavior of the 'adaptive' misfire signal with 1.0% intermittent misfire applied (data taken from a typical 8 cylinder application) and its judgement threshold.
Should one signal cross the threshold, indicating a misfire, the other methods will be skipped in order to prevent multiple counting of the same misfire event.
Scheme 40
Catalyst damage judgement
If 200 revolutions of misfire judgements have been made the monitor will make an assessment as to whether 'catalyst damage' levels of misfire have been exceeded or not. The failure level is determined from a look up table. The sum of individual cylinder misfire counters is then compared against this threshold. If the failure threshold is exceeded then the MIL will illuminate and the appropriate DTCs will be stored.
Storing adaption values in back-up memory
If no misfires have been recorded for the last 'catalyst damage' judgement, and sufficient temporary adaption calculations have been made, the temporary adaption data calculated for each cylinder will be stored in 'back-up' memory, for the appropriate engine speed breakpoint.
If a single misfire is counted for the last 'catalyst damage' judgement, all temporary adaption data will be reset, along with the temporary calculation.
Once data has been stored in memory it can be updated but will not be erased, even after a battery reset.
Excess emissions judgement
If 1000 revolutions of misfire judgements have been made the monitor will make an assessment as to whether 'emissions failure' levels of misfire have been exceeded or not. The failure level is a single threshold value. The sum of individual cylinder misfire counters is compared against this threshold. If the failure threshold is exceeded then the MIL will illuminate and the appropriate DTCs will be stored.
Monitor execution check
Different monitor enable conditions are checked depending upon the operating condition of the engine (for example, fewer conditions apply during engine start). If all the appropriate enable conditions are met the monitor execution flag is set.
Adaptive learning execution check
Specific operating conditions, required for learning misfire 'adaption' values, are checked and the adaption execution flag set as appropriate.
Rough road and low fuel level judgement
A rolling average of 'delta' wheel speed data is calculated from ABS vehicle speed data that is transmitted over the CAN network. This data is compared to calibrated thresholds to determine if the vehicle is being driven over a rough surface that causes misdiagnosis of a misfire. If a rough road judgement is made the appropriate flag is set and taken into account the next time monitor execution conditions are checked.
An additional fault code is stored alongside the misfire fault codes if the fuel level is below a calibrates level. This is to indicate that a possible cause of the misfire fault codes was low fuel level.
It is also possible to block the output of misfire fault codes for low fuel level so long as the on board diagnostic system has not detected a fuel level signal fault. Again this is calibrates and is not used in all applications.
Scheme 41
Scheme 42
Scheme 43
Scheme 44
4.2.3 Drive Cycle Information
- Record flagged DTC(s) and accompanying DTC Monitor freeze frame(s) data.
- Fuel level > 5%.
- Start the engine at a coolant temperature lower than the recorded freeze frame value (from Step 1).
- Drive the vehicle to the recorded freeze frame conditions for 4 minutes. If CHECK ENGINE MIL flashes, lower the engine speed until the flashing stops.
Note regarding misfire monitor DTCs
If, on the first trip, the misfire is severe enough to cause excess exhaust emission, the individual cylinder DTC will be logged. The CHECK ENGINE MIL will not be activated. If the fault reoccurs on the second trip, the individual cylinder DTC will be flagged, and the CHECK ENGINE MIL will be activated. If a misfire is detected on start up (within the first 1000 revolutions) the DTC P0316 will also be flagged.
If, on the first trip, the misfire is severe enough to cause catalyst damage (more severe than excess exhaust emission), the CHECK ENGINE MIL will flash while the fault is present and the individual cylinder DTC will be logged. When the fault is no longer present, the MIL will be deactivated. If the fault reoccurs on the second trip, the CHECK ENGINE MIL will flash while the fault is present and the individual cylinder DTC will be flagged. When the fault is no longer present, the CHECK ENGINE MIL will be activated.
If a misfire DTC is recorded when the fuel level is less than 15%, the DTC P0313 will be recorded.
Scheme 45
4.3.5 Evaporative Emission Canister Purge Valve
The purge flow monitor works continuously and is designed to detect low purge flow caused by a blockage in the purge system or a malfunctioning EVAP canister purge valve.
The basis of the diagnostic is to detect the presence of intake pressure pulses caused by the 10 Hz pulse width modulated control of the EVAP canister purge valve duty ( (Scheme 46)below).
A discrete Fourier transform (DFT) calculation is used to help distinguish these pulses from other noises present in the intake pressure signal.
Scheme 46
Purge operation
Scheme 47
Scheme 48
Scheme 49
Scheme 50
Scheme 51
Scheme 52
Scheme 53
Evaporative system leak faults
- Ensure that fuel filler cap is secure (minimum three clicks)
- Ensure that fuel level is within the range of 15 > 85%
- Ensure that normal "high range" gears are selected
- Ensure that the ambient temperature signal is within the range of 0 > 40 °C (if not, a short drive may be necessary to overcome the filtering used in this signal)
- Ensure that any other DTCs have been rectified (especially if they relate to the purge valve or DMTL heater) and then clear them from the CM memory
- Leave the vehicle to stand undisturbed for at least 3 hours in an environment with ambient temperature within the range of 0 > 40 °C and atmospheric pressure above 70 kPa
- Start the engine and allow to idle for at least 10 minutes
- Switch the engine off and remove the key from the ignition switch
- Allow the vehicle to stand undisturbed for at least 10 minutes
- Switch the ignition back on, wait for 10 seconds, check for DTCs
- If a small leak fault is being investigated this drive cycle will need to be repeated (rough leak check is every drive cycle, small leak check is every other drive cycle)
Purge valve & Purge flow faults
- Ensure that the ambient temperature signal is above 0 °C (if not, a short drive may be necessary to overcome the filtering used in this signal)
- Ensure that any other DTCs have been rectified and then clear them from the CM memory
- Start the engine and allow to idle for at least 10 minutes
- Stop/re-start the engine and allow to idle for a further 5 minutes
- Check for DTCs
4.4.3 Drive Cycle Information
- Start engine and bring to normal operating temperature > 82 °C (180 °F).
- Idle for a minimum of 10 minutes.
4.5.1 Upstream Oxygen Sensor High Low Monitor
This monitor is designed to detect continuous and intermittent faults with the upstream oxygen sensor signals. The monitor will operate continuously provided the entry conditions are met and the monitor is not inhibited for any of the reasons listed in the table.
The upstream oxygen sensors current, voltage and impedance are compared to failure thresholds. If the signals are higher or lower than a predefined amount, a timer is started. A continuous fault flag is set if the timer exceeds a threshold. Otherwise a normal flag is set.
A general flowchart of the operation of the monitor is shown below.
Scheme 54
4.5.2 Upstream Oxygen Sensor Slow Response
The upstream oxygen sensor slow response monitor operates once per drive cycle.
The monitor will be started once all the entry conditions are met. The fuelling is then cycled rich and lean by a set value. The time taken for the upstream oxygen sensors to register this fuelling shift is known. After this has elapsed a calculation of the air fuel ratio read by the sensor is made and divided by the expected increase or decrease.
This ratio is accumulated over a set number of fuelling shifts from rich to lean and lean to rich before a result is obtained. This ratio is lower for a faulty sensor than it is for a correctly functioning part. If the diagnostic produces a ratio that is over a calibrated threshold a "Normal" judgement is made, if the ratio is below the calibrated threshold then the diagnostic will be repeated. If the next measured ratio from the sensor is again below the calibrated threshold then that sensor is faulty and the relevant DTC will be stored and the MIL illuminated. Otherwise, the sensor is judged as fault free.
The flow chart below shows the operation of this monitor.
Scheme 55
4.5.3 Upstream Oxygen Sensor Slow Activation
This monitor is used to check that the upstream oxygen sensors are operating correctly after the upstream oxygen sensor heaters have been turned on.
After the engine has started, the upstream oxygen sensor heaters are activated after a delay time. The monitor checks the change in impedance of the upstream oxygen sensors due to the heating. If the impedance level has not dropped by a defined level in a defined amount of time, then a failure will be detected.
The general flowchart of the monitor is shown below.
Scheme 56
4.5.4 Downstream Oxygen Sensor High or Low Monitor
This monitor checks the downstream oxygen sensor for a circuit fault. There are three parts to this monitor.
- High
- Low or Open circuit
- Short to battery
The short to battery diagnostic is designed to detect a fault that results in a downstream oxygen sensor voltage that is too high (e.g. a short circuit to the battery). If the voltage exceeds the short to battery threshold then a fault counter will be incriminated. When the fault counter exceeds a predetermined value then a fault code will be stored.
The high diagnostic is designed to detect a fault that results in a downstream oxygen sensor voltage that is permanently too high. It monitors the maximum voltage achieved by the downstream oxygen sensor after start. If after a fuel cut the voltage is still too high, but not high enough to detect a short to battery situation, then the downstream oxygen sensor high diagnostic flags a fault.
The low diagnostic is designed to detect a fault that results in a downstream oxygen sensor voltage that is permanently too low. It monitors the minimum voltage achieved by the downstream oxygen sensor after start. If, after the entry conditions are met, the voltage is still too low then a fault counter is incriminated. If the fault counter exceeds a pre-determined value then a fault code will be stored.
A general flow diagram of the operation of this monitor is shown below.
Scheme 57
4.5.5 Downstream Oxygen Sensor Stuck Monitor
This monitor checks if the downstream oxygen sensor voltage has been at the same voltage during an overrun fuel-cut.
The stuck diagnostic is designed to detect if the downstream oxygen sensor voltage is permanently at a voltage that is within its normal operating range. If the entry conditions are met and that the fuel system and oxygen sensors are in working order, the downstream oxygen sensor maximum and minimum voltages are continuously updated. After an overrun fuel-cut has been performed, the difference in voltages before and after the fuel cut is compared. If the difference has not exceeded a threshold then a fault code will be stored.
A general flow chart of the diagnostic is shown below.
Scheme 58
4.5.6 Downstream Oxygen Sensor Rationality Check
This monitor checks that the Sub-Feedback adaption values are within a specified range.
The diagnostic runs if the entry conditions have been met, all the oxygen sensors are working, the fuel system adaptions are within their limits and sub-feedback is operating. The monitor looks at the different sites of the Sub-feedback monitor and checks how many sites are over the fault threshold. If a pre-determined number of sites have exceeded this threshold, then a fault will be detected.
A general flowchart of the operation of this monitor is shown below.
Scheme 59
Scheme 60
Scheme 61
4.5.7 Drive Cycle Information
Upstream (Universal) oxygen sensors
- Engine OFF; cooling fans inoperative > 20 seconds.
- Start engine, coolant< 60°C (140 °F), and bring to normal operating temperature > 82 °C (180 °F).
- Drive vehicle > 1500 RPM for 5 minutes
- Bring vehicle to stop and idle for > 60 seconds
Downstream oxygen sensors
- Start engine and bring to normal operating temperature > 82 °C (180 °F).
- Drive the vehicle steadily between 48 - 97 km/h (30 - 60 mph) for 10 minutes.
- Drive the vehicle above 3000 RPM in 3rd gear at a steady speed. Lift foot completely off accelerator and coast for 30 seconds.
Oxygen sensor heaters
- Start engine and bring to normal operating temperature > 82 °C (180 °F).
- Idle engine for 3 minutes.
Scheme 62
4.10.1 Sensor Stuck
This monitor checks that the ECT sensor is not stuck at a particular value. If the engine has been off for greater than a calibrated time and the engine speed is over a calibrated limit, then the ECT must change by a calibrated amount before the engine oil temperature (EOT) has changed by a calibrated value or a failure will be detected. If the ECT does change by an amount equal to or greater than this threshold then a normal judgement is made.
4.10.2 Range or Performance Failure
The monitor checks that the ECT sensor is reading a correct value when compared to other temperature sensors on the vehicle at ignition on.
If the engine has been off for greater than a calibrated time, then the ECT sensor reading is compared to the average reading of the sum of the intake air temperature (IAT) and ambient air temperature (AAT) sensors. The ECT sensor must be within a calibrated threshold of this value for a normal judgement to be made, otherwise a fault will be detected.
4.10.3 Time to Closed Loop Fuelling
The ECT is monitored to ensure it reaches the closed loop fuelling enable temperature. If the IAT is above the required level, then the following strategy will be enabled.
The timer is incriminated when the engine speed and airflow are above pre-determined thresholds. A normal judgement is made if the ECT reaches the value for closed loop fuelling before the timer reaches the fault threshold.
A failure judgement is made if the load conditions met timer reaches the fault threshold before the ECT reaches the value required for closed loop fuelling.
The fault threshold is obtained from a look up table that is mapped against the ECT at engine start.
Scheme 63
Scheme 64
Scheme 65
4.11.1 High or Low Input Failure and Ground Monitor
This monitor runs continuously. The voltage from the sensor is compared with failure thresholds that are defined in the software.
If the voltage is below the low threshold, then a timer will be incriminated. If this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
If the voltage is over the high threshold, then a timer will be incriminated. If this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
4.11.2 Range/Performance Failure
The monitor runs continuously so long as the entry conditions are met. The Manifold Absolute Pressure (MAP) Sensor monitor compares the measured manifold absolute pressure with an estimated pressure, which is calculated by a model. The model that calculates the estimated pressure uses a look-up table which have engine speed and throttle angle as inputs. These are used to derive base and compensation values for intake air temperature, atmospheric pressure, EGR rate and VVT, from which the estimated pressure is calculated.
Judgements of whether the MAP sensor is behaving correctly are made after the entry conditions have been fulfilled and the differences between the measured and estimated values are below calibrated thresholds. The MAP sensor is faulty if when the entry conditions are met, the difference between the actual and estimated values is greater than a calibrated threshold. The monitor has the ability to make a normal judgement followed by a failed judgement or vice versa as the monitor runs continuously while the entry conditions are met.
Scheme 66
Scheme 67
4.12.1 High or Low Input Failure and Ground Monitor
This monitor runs continuously. The voltage from the sensor is compared with failure thresholds that are defined in the software.
If the voltage is below the low threshold, then a timer will be incriminated. If this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
If the voltage is over the high threshold, then a timer will be incriminated. If this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
For MAF sensor short to ground or open circuit monitoring, then the voltage on the ground pin of the MAF sensor is monitored in the same way as described above.
4.12.2 Range/Performance Failure
The monitor runs continuously so long as the entry conditions are met. The MAF sensor monitor compares the measured airflow with an estimated airflow, which is calculated by a model. The model that calculates the estimated airflow uses a look-up table which has engine speed and throttle angle as inputs. These are used to derive base and compensation values for intake air temperature, atmospheric pressure, EGR rate and VVT, from which the estimated airflow is calculated.
Judgements of whether the MAF sensor is behaving correctly are made after the entry conditions have been fulfilled and the differences between the measured and estimated values are below calibrated thresholds. The MAF sensor is faulty if when the entry conditions are met, the difference between the actual and estimated values is greater than a calibrated threshold. The monitor has the ability to make a normal judgement followed by a failed judgement or vice versa as the monitor runs continuously while the entry conditions are met.
Scheme 68
Scheme 69
4.13 Barometric Pressure Sensor
The Barometric pressure sensor (also referred to as the High Altitude Compensation sensor) is located within the ECM.
4.13.1 High/Low Input Failure
These are continuous monitors. The voltage from the sensor is compared to a failure threshold defined in the software. If the voltage is below the low threshold, then a timer starts to increment. Once this timer exceeds another threshold, then a failure flag is set and a DTC is stored. If the voltage is over the high threshold defined in the software, then a timer starts to increment. Once this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
4.13.2 Range/Performance Failure
The signal from the sensor is compared to the signal from the Manifold Absolute Pressure sensor (MAP) at ignition on only. During this time the pressure within the inlet manifold should be at atmospheric, and therefore should match the value from the barometric pressure sensor.
The following conditions must be met first before the monitor can execute
Engine speed = 0
Vehicle speed = 0
Monitor is not inhibited
Ignition is on
Engine is not cranking
Battery voltage exceeds minimum threshold
Coolant temp above minimum threshold
Atmospheric pressure within limits
Inlet manifold pressure value has settled
If the absolute value of the difference between the signal from the barometric pressure sensor and the MAP sensor differ by more than a defined amount, then a timer is executed. If the timer exceeds a calibrated amount, a temperature failure is judged. Providing there is no failure of the MAP sensor, a DTC is then stored.
Scheme 70
4.14.1 High/Low Input Failure
These are continuous monitors. The voltage from the sensor is compared to a failure threshold defined in the software. If the voltage is below the low threshold, then a timer starts to increment. Once this timer exceeds another threshold, then a failure flag is set and a DTC is stored. If the voltage is over the high threshold defined in the software, then a timer starts to increment. Once this timer exceeds a threshold, then a failure flag is set and a DTC is stored.
4.14.2 Range Performance
Stuck at monitoring executes when closed loop fuel pump control is executing. It checks that the fuel rail pressure signal has varied by at least 3 kPa over a range of demanded fuel pump duties. The maximum and minimum fuel rail pressures are updated each time. The change in demand duty is integrated and the variation between the max and min values is checked. If it is less than 3 kPa, failure judgement is made; otherwise, a normal judgement is made.
4.14.3 Fuel System Pressure
The actual fuel system pressure is compared to the target pressure. If the difference between actual and target pressures exceed the defined thresholds then a failure is registered. If a failure is registered on two consecutive drive cycles then the MIL will be illuminated.
Scheme 71
4.15.1 Sensor Stuck
This monitor checks that the IAT sensor is not stuck at a particular value. If the airflow into the engine is over a threshold for greater than a calibrates time, then the IAT sensor reading is stored. The next time the airflow into the engine drops below a second threshold and the engine is idling, then a second timer is incriminated. Once this timer reaches a pre-determined value, then the IAT sensor reading is stored again. The high flow temperature is subtracted from the low flow temperature and if the difference is greater than a threshold, then a normal judgement will be made. If the result is less than the threshold then a failure will be detected.
4.15.2 Range or Performance Failure
The monitor checks that the IAT sensor is reading a correct value when compared to other sensors on the vehicle.
If the engine has been off for greater than a calibrated time period, then the IAT sensor reading is compared to the average of the sum of the ECT sensor and AAT sensor. The IAT sensor must be within a calibrated threshold of this reading for a normal judgement to be made. If it is outside this threshold then a failure is flagged.
Scheme 72
Scheme 73
Scheme 74
4.16.1 Sensor Stuck
This monitor checks that the engine oil temperature (EOT) sensor is not stuck at a particular value. If the engine has been off for greater than a calibrated and the engine speed is over a calibrated limit, then the EOT must change by a calibrated amount within a set time period after engine start, or a failure will be detected. If the EOT does change by equal to or greater than this threshold a normal judgement is made.
4.16.2 Range or Performance Failure
The monitor checks that the EOT sensor is reading a correct value when compared to other sensors on the vehicle at ignition on.
If the engine has been off for greater than a calibrated time, then the EOT sensor reading is compared to the average of the sum of the ECT sensor and AAT sensor. The EOT sensor must be within a calibrated threshold of this reading for a normal judgement to be made. If it is outside this threshold then a fault will be detected.
Scheme 75
Scheme 76
4.17.1 Sensor Stuck
This monitor checks that the fuel rail temperature (FRT) sensor is not stuck at a particular value. If the engine has been off for greater than a calibrated time, then the next time the engine is started the diagnostic will run.
If the engine speed is over a calibrated limit, then the fuel rail temperature must change by a calibrated amount within a set time after engine start or a failure will be flagged. If the fuel rail temperature does change by equal to or greater than this threshold a normal judgement is made.
4.17.2 Range or Performance Failure
The monitor checks that the fuel rail temperature sensor is reading a correct value when compared to other sensors on the vehicle.
If the engine has been off for greater than a calibrated time period, then when the ignition is next switched on, the fuel rail temperature sensor reading is compared to the average of the sum of the ECT sensor and AAT sensor. The fuel rail temperature sensor must be within a calibrated threshold of this reading for a normal judgement to be made. If it is over this threshold, then a fault will be detected.
Scheme 77
Scheme 78
Scheme 79
4.18 Knock Sensor
When all of the entry conditions have been met, the input signals from the two knock sensors are checked against variable upper and lower threshold levels that are dependent on engine speed. If either sensor input is outside the threshold, then a failure is registered. If a failure is noted on two drive cycles then the MIL will illuminate.
Scheme 80
Scheme 81
Scheme 82
Scheme 83
4.21.1 Crank request Signal
The crank request signal is continually monitored for the presence of a signal while the vehicle is in motion. Vehicle motion is confirmed by checking vehicle speed, engine speed and engine load. If the crank request signal is detected for longer than the defined time a failure is registered.
4.21.2 Park/Neutral Switch
During the engine crank operation if the park/neutral input is low, with the CAN signal from the transmission indicating park/neutral is selected; the low fault timer is enabled. When the low fault timer reaches the calibrated time, the low fault flag is set.
If the park/neutral input is high, and the vehicle is detected as moving with an appropriate engine load, then the high fault timer will be enabled. When the high fault timer reaches the calibrated time, the high fault flag is set.
4.21.3 Starter relay
The starter relay is controlled by the ECM in response to a valid crank request signal when the vehicle is stationary and park or neutral are selected. A failure of the starter relay circuit will be registered if the starter relay drive signal from the ECM is on but the starter relay feedback indicates that the relay is off.
Scheme 84
4.28 Variable Valve Timing
The system comprises of an actuator built into the camshaft chain sprocket and an oil control valve which controls the flow of oil to the camshaft actuator. Control of the system is done via the oil control valve and camshaft position sensors. The oil control valve varies the oil flow into the camshaft actuator and creates a variable offset between the camshaft and the camshaft sprocket, feedback for this system is provided by the camshaft position sensors. Variable valve timing is only fitted to naturally aspirated engines.
4.28.1 Hardware Check
This monitor checks the oil control valve on both banks 1 and 2. The commanded and actual state of the oil control valve are continually checked as long as the PWM drive signal remains within limits. If the commanded and actual state of the oil control valve differ for longer than a predefined time period then a failure is registered. The ECM determines the type of failure by examining which state the valve was unable to attain and the output signal to the valve. If a failure is registered on 2 drive cycles, the MIL will illuminate.
4.28.2 Camshaft Position
The camshaft position sensors are used to monitor the actual level of camshaft advance/retard against the target level. If the target and actual values do not match a failure is registered. If a failure is registered on 2 drive cycles, the MIL will illuminate.
4.28.3 Camshaft Adaption
The adaption values for the camshaft position on this trip are compared to the adaption values form the last trip. If the adaption values vary by more than a defined amount a failure is registered and the MIL is illuminated.
Scheme 85
Scheme 86
4.29 Cold Start Emission Reduction Strategy
Once all entry conditions have been met this monitor performs two tests
The first checks the actual engine speed against the target idle speed. If the ECM is unable to achieve a high enough idle speed (actual idle speed lower than target idle speed by more than 100 RPM) then a failure will be registered.
The second check compares the actual spark timing against a predefined target. If the spark timing is too far advanced then a failure will be registered.
In both instances should the failure be detected on two consecutive drive cycles the MIL will be illuminated.
Scheme 87
4.30 Secondary Air Injection System
Observing the system pressure at several instances during its cycle of operation monitors the secondary air injection system.
The system pressure is measured before operation of the pump. The pump is then switched on simultaneously with the opening of the check valve. After a delay to allow the system to stabilize, the system pressure is measured again, this time by taking the average of a 1-second duration of readings, and normalizing for variations in battery voltage and atmospheric pressure.
A second pressure measurement is made after the requirement for secondary air injection into the exhaust system has expired, but continuing on from the same period of pump operation, i.e. the pump is left running, against a closed check valve. Again this pressure measurement is the average of a 1-second duration of readings normalized for variations in battery voltage and atmospheric pressure. If the system pressure measured at this time has not risen enough or has risen too much with respect to the system pressure during normal operation of secondary air injection then a failure will be flagged.
This strategy can detect a single point failure anywhere in the system as shown below
Scheme 88
Scheme 89
Scheme 90
Scheme 91
Scheme 92
Scheme 93
Scheme 94
Scheme 95
4.31 Controller Area Network System
The Controller area network (CAN) system is monitored by the ECM for the following conditions.
4.31.1 Invalid signal Error
The ECM is continually receiving data from a number of other control modules via the CAN system. If one of these control module identifies a problem within its own system that cause it to be unable to transmit valid data, it will a store DTC locally and transmit an error marker (a specific default value of the data that indicates an error) on to the CAN system. When the ECM identifies an error marker from another control module, it also logs a failure.
4.31.2 Loss of Communications
All of the control modules on the CAN system transmit data continually. If messages from one or more of the control modules are not seen by the ECM within a predefined time, it will register a loss of communications failure.
Scheme 96
4.32 Fuel Level Sensor
The fuel level is monitored continuously. The fuel level should change by more than a set percentage before a calculated amount of fuel is used. This process will operate through cumulative trips if necessary. Once the fuel level changes by the amount required the process is reset and begins again. If the fuel used threshold is reached before the fuel level changes by the required percentage, a fault will be stored.
Scheme 97
Rationality Check
The signal is check for rationality against the IAT sensor. When the entry conditions have been met the difference between the sensors is checked, if this is greater than the threshold for a predefined period then a failure is registered. If the problem occurs on two drive cycles then the MIL will illuminate. Which DTC logs depends on whether the ambient air temperature sensor signal is lower or higher than the intake air temperature sensor.
Scheme 98
4.35 Intake Manifold Tuning Valve System
When the entry conditions have been met, the control module checks the commanded versus actual position of the IMT valves. If they are not matched, a timer is started. If at the end of the set time the commanded and actual positions of the IMT valves do not match then the relevant DTC is flagged and the IMT valve affected is disabled.
