Self Diagnosis - Theory & Operation (s85) BMW M6 E63/E64

DIAGNOSTIC TROUBLE CODE INDEX

DIAGNOSTIC TROUBLE CODE INDEX (THEORY & OPERATION)

Diagnostic Overview

The ECM tests the catalyst system during steady state driving by cycling the fueling LEAN and then RICH for a calibrated number of cycles while monitoring the oxygen storage capacity (OSC). Prior to the Catalyst test the canister purge valve is almost closed. This is to eliminate the influence of canister vapors on the downstream sensor during the test procedure.

The first lean to rich cycles of the test is only used to establish an average voltage value of the downstream sensor voltage. During subsequent cycles the OSC is based on the integrated (accumulated) value of the difference between the average value of the previous lean to rich cycle and the measured instantaneous voltage during the current lean to rich cycle.

Monitoring Conditions

1. closed loop conditions
2. calculated catalyst temperature > threshold
3. no fuel cut-off conditions, engine in part-load
4. O2 sensors downstream active
5. O2 sensor upstream active
6. canister purge system is reduced
7. engine speed
8. engine load
9. vehicle speed
10. not too high engine dynamic condition
11. engine coolant temperature not too low
12. no malfunctions of: lambda-control Vehicle speed O2 sensor heater O2 sensor deterioration, upstream O2 sensor deterioration, downstream No misfire Throttle valve Purge System Fuel System

The input parameter used for monitoring is the O2 sensor voltage downstream. catalyst.

Monitoring Function

Catalyst monitoring is based on the monitoring of the oxygen storage capability by comparing the signals of the O2 sensor upstream and downstream the catalyst.

The engine control results in regular lambda oscillations of the exhaust gas. These oscillations are damped by the storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream the catalyst indicates the oxygen storage capability.

If all monitoring conditions are fulfilled, then a special defined A/F-modulation will be done. The relation of the deviations between the current downstream-sensor-signal to the average value of the downstream-sensor-signal is a criteria for catalyst condition. The catalyst system is considered malfunctioning, if after a specified number of monitoring cycles the average of the ratios exceeds a threshold. The corresponding fault code is stored.

The ion current technology gives the possibility to detect misfire according to the requirements of the law (Europe and USA). Misfire is defined by non- or insufficient-appearances of combustion inside the cylinder (e.g. because of spark or injection failures).

Measurement Principle

A constant measurement voltage is applied to the spark plug immediate after the ignition spark. The chemical process of combustion produces free electrons and ions. Hence, some electrical current is flowing, which is measured and analyzed.

Ion Current Waveform Characteristic

Basically, the shape of the measured ion current can be separated in four parts.

Scheme 254

The first part starts immediate after ignition and as long the ignition spark is present. At this time (Spark-Time) a high negative current is flowing, which is constrained to zero by the measurement circuit. The second part starts at the point the coil energy remaining is not sufficient to keep the spark alive. The coil and measurement part build a R-L-C circuit, which causes an oscillating current out of the remaining coil energy. The third part is the ionization cause by the flame front (chemical ionization). At this point the air fuel mixture starts to burn. The fourth and last part corresponds to the internal cylinder pressure and reflects a high ionization caused by the high temperature and the combustion process.

Misfire Detection Method

Misfire caused by spark failure or combustion failure can be distinct. Spark failures are detected by measuring the time immediate after ignition until the remaining coil energy yields into an oscillation current. Spark failures are caused due insufficient short sparks or no sparks at all. A to short spark is typically caused by short-circuit on the spark plug or an insufficient charged ignition coil. The short spark does not ignite the fuel-air mixture. Hence, no further ionization is produced after the oscillation current from the remaining coil energy.

Scheme 255

In case no spark is produced at all, there is whether the high negative current during the spark neither any further ionization caused by the flame front or combustion process.

Scheme 256

In order to detect misfire caused by combustion failure, the ion current is integrated over the misfire window. The misfire window covers the area of ionization caused by the combustion process and partly the ionization cause by the flame front. If the calculated integral not fulfills a sufficient value according engine load and revs, a combustion failure misfire is detected.

Scheme 257

Cylinder Individual Misfire Detection

Any combustion of every cylinder the ion current is measured. The ion current waveform is used to calculate the spark-time and combustion integral value. Ignition misfire will be detected due an insufficient short spark-time or maximum measured spark-time (missing spark). If the combustion integral value not fulfills a sufficient value according engine load and revs, a combustion failure misfire is detected. In case an ion current satellite error or an ion current signal error is present, the entire engine bank is switched off respectively.

Ignition Failure Test Conditions

The thresholds of the spark-time are tested, as soon as following activation conditions are given

1. No fuel cut-off (checked cylinder individual)

Combustion Failure Test Conditions

The combustion integral value is tested, as soon as following activation conditions are given

1. No fuel cut-off (checked cylinder individual)
2. Engine speed not too low (> 500 RPM)
3. Engine load not too low (minimum torque line)
4. No high transients of engine torque
5. Engine ignition position gradient

Statistic Fault Protection of Catalytic Converter

The catalytic convert of each engine bank is monitored within an interval of 200 crankshaft revolutions periodically. Misfire detected are weighted (over engine load and revs) and added for each engine bank separately. As soon as the bank sum counter exceeds a predetermined value, an error report for each cylinder with misfire is stored. Additionally, the MIL is switched on immediately and the worst cylinder is switched off (injection off and lambda control switched to open loop). If more then one cylinder did have misfire an error report for multiple cylinder will be stored.

Detection Unacceptable Increase of Emissions

This section describes the detection of unacceptable increase of emissions (according to OBDII-regulations).

If the sum of cylinder(s) misfire counters within 1000 revolutions is 4 times exceeding a predetermined value during a driving cycle, or during the first 1000 revolutions, the fault code for emission relevant misfiring is temporarily stored. If the following driving cycle is also above the emission limits, the MIL will be switched on and a cylinder selective or global fault will be stored.

If more than one cylinder is misfiring, all misfiring cylinders will be specified and the fault code for multiple misfiring cylinder will be stored. If one cylinder incorporates 90% of all misfire, an error report for this cylinder will be stored only.

The error report stored for any cylinder, which did not have any misfire during the interval of 1000 crankshaft revolutions, will be cleared. The error report for multiple cylinder will be cleared, if no cylinder did have any misfire. At the end of each interval all counters are reset to its initial values.

The ion current technology allows the possibility to detect misfire and knocking combustion over a wide range of engine speed and load.

Misfire is defined by non- or insufficient-appearances of combustion inside the cylinder (e.g. because of spark or injection failures). The traditional way of engine misfire detection is based on monitoring the crankshaft acceleration. Especially on a V10 engine concept and high revs, it is very difficult to distinct between normal engine roughness and misfire events. Applying the ion current technology enables detection of combustion or sparking misfire on nearly any engine speed and load range.

In spark ignition engines, knock can be defined as self-ignition of a certain portion of the unburned gas beyond the flame front. This abnormal combustion releases a chemical energy that excites within the cylinder volume pressure oscillations that are responsible of engine noise and sometimes damage. Therefore, knock is undesirable process that has to be avoided. At high revs the known and conventional knock sensor technology is not sufficient enough for the V10 engine concept.

System Architecture Overview

A constant measurement voltage is applied to the spark plug, after the ignition spark has been applied immediately. The chemical and temperature process of combustion produces free electrons and ions. Hence, some electrical current is flowing, which is measured and analyzed.

Scheme 258

The V10 engine (S85) is spitted in two engine banks (five cylinders each). One ion current satellite unit is dedicated for each bank. In order to reduce SNR (Signal Noise Ratio), especially to improve the accuracy of knock detection, amplification has been introduced. The amplification is controlled by the ECU applying two different measurement voltages and two different amplification gains. The cylinder individual ion currents signals from the ignition coils are amplified and multiplexed send to the ECU (MS_S65).

Ion Current Satellite Monitoring Algorithm

The amplification of each ion current satellite is controlled by the ECU via driver stages for gain and voltage. Those driver stages are monitored separately. Furthermore, the multiplexed ion current signal from each satellite is monitored for the entire bank. Additionally, two different internal satellite errors can be detected.

For both driver stages the same diagnosis is applied, which enables to detect short circuit to ground, short circuit to battery and open load.

The evaporative system monitoring permits the detection of leaks in the evaporative system with a diameter of 0.5 mm and up.

1. Ignition off
2. Engine start temperature
3. Ambient temperature
4. Ambient pressure
5. Engine speed
6. Vehicle speed
7. Fuel tank level
8. Battery voltage
9. Soak and running time
10. No malfunctions of: Battery voltage Ambient temperature Vehicle speed ambient pressure Relative-time

Scheme 259

Scheme 260

Scheme 261

Description of chart

This chart describes the diagnostic frequency for the case where refueling is detected and there is no leak in the tank. The reason for this chart is to demonstrate the capability of the "check filler cap" diagnostic. The tank was refilled before the start of the first driving cycle. The first diagnostic is performed while driving to check if the filler cap was replaced. Afterwards, two normal diagnostic cycles are performed.

Scheme 262

Description of chart

This chart describes the diagnostic frequency for the case where refuelling is detected and the filler cap is left open. The filler cap diagnosis is done during the first driving cycle, as soon as the refuelling has been detected.

Because of the "check filler cap" message, the driver can fix the most common reason for system leaks. So the evaporative emissions are reduced compared to systems without "check filler cap" message.

To give the driver time for closing the filler cap without illuminating the MIL, the first "Leak supposed"-flag is ignored.

Scheme 263

Description of chart

The chart above describes the case where refueling is detected, the filler cap is left open and the "check filler cap" message is ignored by the driver. While driving the "check filler cap" message will illuminate in the panel immediately after a leak diagnostic is performed. During soak, another leak diagnostic is performed. The flag "leak supposed" is set. After restarting the engine the "check filler cap" message will again be displayed immediately in the panel. The MIL will be illuminated after an additional two driving cycles.

By means of a D iagnostic M odule_ T ank L eakage (DM_TL), an electrically actuated pump located at the atmospheric connection of the evaporative canister, a pressure test of the evaporative system is performed in the following order

Scheme 264

Scheme 265

Scheme 266

1. During the reference leak measurement, the electrically actuated pump delivers through the reference restriction. The engine-management system measures the pump's electrical current consumption in this phase.
2. During the Leak Measurement, the electrically actuated pump delivers through the charcoal canister into the fuel-tank system. The pressure in the evaporative system may be up to 25 hPa depending on the fuel level in the tank. The engine-management system measures the pump's electrical current consumption. A comparison of the currents of the reference leak measurement and the leak measurement is an indication of the leakage in the tank.
3. After the test the remaining pressure in the evaporative system is bled off through the charcoal canister by switching off the pump and solenoid valve.

Evaporative Purge System

The Evaporative purge system consists of one charcoal canister and two purge valves, one for each cylinder bank. The system check includes an electrical and a rationality check of the purge valves.

1. Ignition on
2. Battery voltage

A smart low driver performs the testing. It compares current trough the driver in on-condition with an open load threshold. A short to battery is detected by an over current. In off-condition the voltage level is compared with a low limit to detect short to ground.

When the engine is in a stable idle condition, the purge valves are opened and closed. The deviation of some engine parameters is the sign for a mass flow through the valve.

1. Ignition on
2. Battery voltage
3. Engine speed
4. Engine load
5. Engine status
6. Vehicle speed
7. Lambda controller
8. Leak detection not active
9. No malfunctions of: Purge valve Lambda-control O2 sensor, upstream Fuel System Air - System Vehicle speed Ion measurement system Throttle valve

When the engine has reached idle condition, the purge valves are closed.

After the engine has settled for a moment, the purge valves are opened and closed.

The deviation of the following engine parameters are monitored

1. Lambda of each cylinder bank
2. Ion current integral of each cylinder bank
3. Engine speed and air mass

Because of different charcoal canister loads, different parameters of the engine will change.

If one parameter deviates more than the threshold, the corresponding purge valve is counted as good.

This procedure is repeated several times.

As soon as one purge valve has enough good-counts, the flow check for this valve is finished successfully.

If at the end one ore both purge valves have not enough good-counts, a fault code is stored for the corresponding purge valve.

The fuel level system has two different sensors. Each is placed in one side (left and right) of the fuel tank.

1. ignition on
2. can-message from instrument received and valid

The resistance of the fuel level sensors must be within the valid range.

If one or both sensors leave the valid range for a certain time, a fault code is stored.

The ECU compares his own calculated fuel consumption with the fuel level sensor.

1. Ignition on
2. CAN Message no error
3. Sensor resistance no error

At the beginning of the rationality check the fuel consumption is reset and the actual fuel level is stored. Then the fuel consumption is continuously summed up, until the diagnostic volume is reached. Then the difference between stored and actual fuel level is calculated and compared with the diagnostic volume. If the deviation is too large, a fault code is stored.

If refueling is detected, the rationality is reset.

If the fuel level sensors signs almost or complete full tank, no refueling can be detected with the sensors. So the fuel consumption is reset, if ignition is switched off because refueling is possible. If the consumption exceeds a threshold, and the fuel level sensors signs still almost full, a fault code "stuck full" is stored.

The pumping work of the pistons is transmitted in the form of air vibrations through the crankcase and the diagnosed hose connection into the plenum chamber and to the hot-film air-flow sensor (HFM).

If the hose connection is unconnected there are no noticeable vibrations in the HFM signal. The vibrations of the HFM signal are integrated for a certain period of time and compared to a defined threshold.

1. Engine running time till start
2. Engine runs in idle mode for a certain time
3. Engine temperature
4. Oil temperature
5. Vehicle speed = 0
6. Ambient air pressure > 750 mb
7. no malfunctions of: Vehicle speed error Ambient air pressure error Hot-film air-flow sensor error Variable camshaft phasing error Misfire detection error

If the monitoring conditions are compliant the vibrations of the HFM-sensor signal are integrated and averaged over several time windows (at present 3).

If this value is higher than a certain threshold the PCV system is operating properly.

If the value is lower than the threshold the PCV system is not operating properly.

Scheme 267

The purpose of this diagnosis is to detect electrical faults as defined in OBDII requirements. The input signal is analog from CAN. If an error is present on CAN signal, an error symptom is set and an error counter is de-bounced.

Additionally the rationality of the outside temperature sensor signal is compared to a model.

1. no malfunction in engine temperature
2. no malfunction in relative time measurement
3. no malfunction in vehicle-speed
4. no malfunction in intake air temperature (IAT) (OBD
5. no malfunction in mass air flow
6. no malfunction in CAN-connection to instrument-cluster
7. no malfunction in outside temperature signal from instrument-cluster via CAN-bus (driving vehicle with at minimum moderate city speeds and a reasonable air mass flow)
8. engine status: running
9. IAT below a threshold
10. Fuel cut-off less than 5 seconds
11. During warm-up after cold start

Monitoring Function: Electrical diagnostics

The actual electrical diagnostics is accomplished by the instrument cluster and transmitted via CAN.

An invalid, received ID is evaluated as electrical error.

Monitoring Function: Rationality check

The rationality of the ambient temperature is check with an IAT-based model. As soon as the difference between model and ambient temperature exceeds a threshold, the error counter starts to increase. As soon as the counter exceeds a threshold a fault is set.

Given steady IAT conditions or whilst warm-up cycle after a cold start, the ambient temperature is permanently compared to the model.

In very unsteady IAT conditions (e.g. after an up-heating period with idling or slow moving vehicle or after a warmstart) the diagnostics is suspended and is re-enabled after increasingly stabilizing IAT conditions.

The fuel system monitoring is monitoring for permanent deviations of the A/F controller (lean and rich) from the mean position. After the enable conditions are met, a counter is started. At this point the ECM evaluates the total percentage of short and long term fuel control.

Scheme 268

1. closed loop conditions
2. engine coolant temperature not to low
3. engine load
4. engine speed
5. no inhibition due to fuel dilution of oil
6. intake temperature
7. altitude not too high
8. no malfunctions of: O2 sensor heater O2 sensor deterioration, upstream No misfire Throttle valve Mass airflow sensor Canister purge valve Cam sensor Coolant temp, sensor Ambient pressure sensor

If the fuel system is suddenly and significantly disturbed (e.g. by a leaky injection valve) and the A/F controller reaches its restriction or a permanent deviation from the mean position reaches the additional lean or rich thresholds and the accumulated time (sum of all excesses for rich and lean) is greater than a fixed limit during a defined period, a fault for long term trim will be detected and stored.

If a lean condition is present and total fuel control is above the calibrated threshold a timer is started. If the lean threshold counter exceeds the calibrated threshold within the diagnostic time, a lean error is set.

If a rich condition is present and total fuel control is below the calibrated threshold a timer is started. If the rich threshold counter exceeds the calibrated threshold within the diagnostic time, a rich error is set.

The Fuel System and the Fuel Rail Pressure Sensor are checked for functionality. The diagnosis runs every driving cycle. In order to ensure the functionality of the fuel system with a rate-controlled variable system pressure, the pressure is checked continuously with the Fuel Rail Pressure Sensor (FRPS).

The plausibility of the sensor is check immediately after engine start in comparison to the mechanical fuel pressure regulator.

1. ECT inside temperature frame
2. engine running
3. No fuel cut-off
4. battery voltage higher than threshold

FRPS plausibility in comparison to the mechanical fuel pressure regulator

The plausibility of the FRPS is checked after every engine start, with both fuel pumps operating at full load. Since the fuel flow at engine idle speed is very low the fuel pressure is just limited through the mechanical fuel pressure regulator, which limits the maximum fuel system pressure to a constant value. In case the FRPS value diverges more than a certain threshold from this value an error of the FRPS is detected.

Fuel pressure deviation at rate-controlled pressure operation

During engine operation at partial load, the fuel system operates with a variable fuel pressure. If the fuel pressure diverges from the target value more than a threshold an error of the fuel system at rate-controlled operation is detected.

Fuel pressure deviation at maximum flow

During engine operation at high load, the fuel system supplies a high flow and operates with both fuel pumps operating at 100% providing a high constant fuel pressure. If the fuel pressure diverges from the target value more than a threshold an error of the fuel system at max. flow is detected.

To cover a long time fuel system shift in lean or rich direction the closed loop controller and the closed loop long term adaptations will be observed by a diagnostic strategy.

The strategy is split in two different parts, whereby one part is monitoring if the closed loop controller reaches its limit (rich or lean) - Closed loop controller diagnostic. The other part is monitoring if the closed loop system long term adaptation reaches its limit (rich or lean) - Closed loop adaptation diagnostic.

In both strategies a timer will start as soon as the limit is reached. After the timer has expired and the limit is still reached, a malfunction will be set.

1. closed loop conditions
2. no fuel cutoff conditions
3. engine speed
4. engine load/torque
5. canister loading not too high if purge system active
6. engine coolant temperature not to low
7. no malfunctions of: O2 sensor heater O2 sensor deterioration, upstream No misfire Throttle valve Mass airflow sensor Canister purge valve Cam sensor Coolant temp, sensor Ambient pressure sensor Purge system, fuel system

Similar Conditions Function

When the engine management system recognizes a failure in the misfire or fuel systems, the engine management system is required to record the conditions present when the fault occurred. These conditions recorded include engine speed, engine load (MAF), and warm up status of the first event that resulted in the storage of a code. These conditions stored are referred to as similar conditions

Once the similar conditions are meant without a failure in the misfire or fuel system, the flag is set to 1. Once this flag is set the driving cycle counter for that failure can be determined.

The code and stored freeze frame conditions may be erased if similar conditions are not encountered during the next 80 driving cycles immediately following the initial detection of the malfunction.

The MIL may be extinguished after three sequential driving cycles in which similar conditions have been encountered without an exceeding the thresholds of the fuel system diagnostic.

To cover aging effects in the emission related exhaust system, for parts like catalysts as well as pre- and post oxygen sensors, a fuel trim strategy is used. As a part of the fuel trim the post oxygen sensor signal is taken into account.

For shifting the post oxygen sensor signal on a certain voltage level, the closed loop controller is used. The expected rear oxygen sensor signal is compared to the current signal. As long as the expected value is not reached, the closed loop controller is shifting the system by a certain amount of proportional or integral share. The outcome is a corrected lambda value (fuel trim value is added to the base fuel calculation).

In case it is not possible to shift the system on the expected level, the fuel trim diagnostic which cover validation of the proportional/integral value of the fuel trim. The fuel trim data will be compare with a application threshold. As soon as the threshold is exceeded a malfunction code will be set for the specific criteria.

It is to mention that before a malfunction for trim control is set, a validation of front and post oxygen sensor is performed through introducing a rich/lean shift. Please see also within the description of linear oxygen sensor monitoring.

The input parameters used for monitoring are

1. p- share of lambda trim control
2. i - share of lambda trim control
3. engine load
4. engine speed
5. engine coolant
6. canister load
7. vehicle speed

The enable conditions for the monitoring are

1. trim control active (and lambda control active)
2. limited dynamic for load, speed and lambda controller
3. secondary air system not active
4. no malfunctions of: air mass flow sensor plausibility secondary air system fuel system monitoring downstream oxygen sensor circuit downstream oxygen sensor heater circuit upstream oxygen sensor dynamic upstream oxygen sensor heater coupling (All other upstream and downstream oxygen sensor malfunctions deactivate lambda control or trim control directly)

Monitoring function: P- / I-Share

The trim control plausibility monitoring detects a high deviation of the l-share of lambda trim control or exceeding the number of P-jumps greater than an application threshold. If this happens the following malfunction is detected

Fuel trim above limit - system too lean or system too rich

If the mentioned malfunction is detected, the corresponding fault code is stored.

Malfunction for I-share

For fuel trim system too lean: P2096 / P2098

For fuel trim system too rich: P2097 / P2099

Malfunction for P-share

For fuel trim system too rich: P114A / P114C

For fuel trim system too lean: P114B / P114D

Diagnostic overview: Upstream Oxygen Sensor Monitoring (linear)

The oxygen sensor monitoring is a very complex diagnostic and in the following split into different chapters like

1. Electrical diagnostic of the sensor short ground/batt openload diagnostic manager
2. WRAF Sensor controller monitoring
3. Oxygen Sensor Signal Activity Check Sensor disconnected from exhaust Sensor signal up-stream (plausibility) Sensor signal in fuel cut off
4. Sensor signal dynamic monitoring (slow response)
5. Heater monitoring

The input parameters used for monitoring are

1. error information from oxygen sensor microcontroller (ATIC42 - Siemens)

The enable conditions for the monitoring are

1. oxygen sensor microcontroller active
2. battery voltage not too low
3. no oxygen sensor circuit malfunction

The oxygen sensor circuit monitoring detects the following malfunctions by evaluating the error information received from oxygen sensor microcontroller

1. Short circuit of sensor signal to battery voltage
2. Short circuit of sensor signal to ECM ground

If one of the above mentioned malfunctions is detected, the corresponding fault code is stored.

Monitoring Overview: (openload) linear sensor

This function determines, if an open circuit in any of the four electric lines (Reference Voltage, Virtual Ground, Pumping Current and Trim Current) is present in the WRAF Sensor.

This function shall be triggered only if one of the following diagnosis is active (to set the readiness bit), which are Plausibility Check, Plausibility during fuel cutoff, and Sensor Heater OBD2. The function shall go to the state = "active" only if one of the above diagnosis denounced a fault. In this state, if a heater OBD2 error exists, the WRAF sensor controller oscillator used to measure the sensor internal resistance shall be disabled in order to allow a stable plausibility error detection. After the deactivation of this function the oscillator shall be reactivate. During the diagnosis state "active" a timer shall run waiting for OBD2 heater monitor to complete. If a heater OBD2 error could be detected, the timer should be stopped and a symptom set, otherwise it should run until it reaches the max value.

Reference Voltage (UN - openload): If a heater error and a plausibility error (symptom "sensor too rich/lean") or an open circuit error in the line Reference Voltage exists.

Virtual Ground (VG - openload) and Pumping Current (IP - openload): The sensor non-activity can be detected by anyone of the following diagnosis: plausibility (symptom is "sensor not active"), or plausibility during PUC (symptom signal too low). It is assumed that no heater OBD2 fault exists. Both malfunctions criteria will lead to the same P-Codes, since there is no technical possibility separate the symptoms.

Trim Current (IA-openload): If the sensor shows an augmented gain, i.e. the sensor signal is higher than the nominal characteristic line, the plausibility test during the fuel cutoff phase shall detect this symptom and an open circuit is assigned to the line Trim Current.

The input parameters used for monitoring are

1. error information from oxygen sensor microcontroller

The enable conditions for the monitoring are

1. oxygen sensor microcontroller active
2. battery voltage not too low
3. no oxygen sensor circuit malfunction

The oxygen sensor circuit monitoring detects the following malfunctions by evaluating the error information received from oxygen sensor monitoring functions

OXYGEN SENSOR MONITORING FUNCTIONS CHART

If one of the above mentioned malfunctions is detected, the corresponding fault code is stored.

Oxygen Sensor Diagnosis Manager

Diagnosis Manager for open load diagnostic.

Scheme 269

This functions shall detect an error of a WRAF sensor controller (ATIC42), which uses an SPI communication.

1. SPI-Check between ATIC42 and controller (P3022/3023): This function shall detect the communication between ATIC42 and the controller. This is used to determine if the function is working properly. After an ECU reset, the WRAF sensor controller is started and the diagnosis determines the communication with a checksum, witch transfer above SPI. If not the same valve come above SPI, then a DTC will be stored.
2. Heater Controller - Ri-Adaptation diagnostic (P3016/P3017/P3032/P3033): The offset adaptation for the heater resistance is performed by disconnecting the o2-sensor from the o2 controller. This is done by a SPI-command. That gives the possibility to create a condition within the controller for measuring the deviation compared to the "neutral point". The measured deviation is taken as adaptation value. The gain diagnostic is covering a deviation of the internal resistance of the oxygen sensor compare to the given reference resistance out of the sensor controller. For measuring the reference value, a SPI-command is used to trigger an internal measurement (in the controller). The diagnostic value is the ratio of both values. In case the value is too high a malfunction will be set.

Diagnostic Overview: P2414/P2415

The oxygen sensor signal activity check monitors if the sensor is attached to the exhaust pipe. A malfunction is detected if the oxygen sensor voltage is outside a calibrated threshold

1. Sensor not active during part load conditions

If the above mentioned malfunction is detected, the corresponding fault code is stored.

The enable conditions for the monitoring are

1. oxygen sensor voltage
2. upstream oxygen sensor operability detected
3. no fuel cut-off or idle speed
4. no misfire
5. no malfunctions of: upstream oxygen sensor air mass flow sensor injection valve fuel system

The enable conditions for the monitoring are

1. oxygen sensor voltage
2. upstream oxygen sensor operability detected
3. no fuel cut-off
4. no misfire
5. load within limits
6. exhaust temperature within limits
7. no malfunctions of: upstream oxygen sensor circuit upstream oxygen sensor heater circuit air mass flow sensor coolant sensor (ECT) throttle valve engine safety program VANOS injection valve fuel system

Monitoring Function: P2195 - P2196 - P2197 - P2198

This monitor is an enhancement of the Fuel Correction Diagnosis. Its purpose is to help determine the root cause of the failure for fuel correction. The monitor will only be enabled if a fuel correction fault has been detected and a malfunction code has been stored, i.e., P2096 - P2097 - P2098 - P2099.

If a fuel trim malfunction exists, this diagnosis will be enabled to determine if the root cause of the malfunction is due to a stuck signal of the upstream O2 sensor or a system malfunction, i.e. vacuum leak, injector, post oxygen sensor etc...

If it has been determined that the O2 signal was the root cause of the fuel correction fault, the appropriate DTC will be stored along with the fuel correction DTC.

The enable conditions for the monitoring are

1. oxygen sensor voltage
2. fuel cut-off
3. no misfire
4. engine temperature within limits
5. no malfunctions of: upstream oxygen sensor circuit upstream oxygen sensor heater circuit air mass flow sensor coolant sensor (ECT) throttle valve engine safety program VANOS injection valve fuel system

Monitoring Function: P2297 - P2298

The diagnosis detect a faulty oxygen sensor if the sensor front signal not plausible in fuel cut off.

If the above mentioned malfunction is detected, the corresponding fault code is stored.

The input parameters used for monitoring are

1. air-fuel mixture ratio (converted from oxygen sensor voltage)
2. maps containing the nominal and the minimum lambda amplitude (function of engine speed and load).

The enable conditions for the monitoring are

1. oxygen sensor signal dynamic monitoring not finished
2. upstream oxygen sensor operability detected
3. upstream oxygen sensor heater active
4. secondary air system not active
5. forced stimulation of lambda controller active and within limits
6. enable conditions for catalyst efficiency monitoring fulfilled
7. engine speed within limits
8. load within limits
9. no malfunctions of: upstream oxygen sensor circuit upstream oxygen sensor heater circuit air mass flow sensor coolant sensor (ECT) throttle valve engine safety program VANOS

The oxygen sensor signal dynamic monitoring detects greater deviations of the dynamic behavior of the sensor signal compared to the nominal behavior, controlled by the lambda controller.

The change of the dynamic behavior is caused by problems of the electrical connection (e.g. open circuit), extreme aging of the sensor or a low sensor temperature which slows down the sensor compared to the nominal behavior.

The monitoring is based on an amplitude criterion, i.e. an air-fuel mixture forced stimulation is imposed and the lambda controller amplitude is measured. The result is normalized with the nominal amplification of a nominal oxygen sensor and the minimum amplification of a slow oxygen sensor (both stored in a calibration map). In case the normalized amplitude factor is lower than the calibrated threshold, a symptom is present and is validated by checking if no oxygen sensor open circuit was already detected. Once the symptom is valid the following malfunction is detected

1. Sensor signal too slow

If the above mentioned malfunction is detected, the corresponding fault code is stored.

The purpose of this monitor is to detect errors within the O2 Sensor Heater Circuit. The signal for the O2 sensor heater is pulse-width modulated. The signal of the powerstage is monitored internally by the driver.

The input parameters used for monitoring are

1. error information from power stage

The enable conditions for the monitoring are

1. battery voltage not too low
2. ignition on

The oxygen sensor heater circuit monitoring detects the following malfunctions by evaluating the error information received from the power stage

1. HO2S Up SCVB
2. HO2S Up SCG
3. HO2S Up Open circuit

If one of the above mentioned malfunctions is detected, the corresponding fault code is stored.

In order for the oxygen sensor to function properly, the sensor element must be heated. A non-functional heater delays the sensor readiness for closed loop control and influences emissions.

1. battery voltage above threshold
2. O2 sensor heater in operation
3. delay time for sensor warming up
4. no O2 sensor malfunction
5. oxygen sensor heater circuit

The monitoring function measures continuously both the sensor heater current as well as the heater voltage (heater supply voltage) to calculate the sensor heater resistance. The monitoring strategy is based on the comparison of the O2 sensor heater resistance to a calibrated threshold. If the heater resistance fall below or exceeds the threshold, an O2 sensor heater malfunction is detected.

Scheme 270

The purpose of this function is to detect oxygen sensor heater failures that would lead to an increase in emissions beyond the thresholds stated in the appropriate regulations. The diagnosis shall be carried out by determining whether the operative readiness of the sensor exceeds a time threshold, or whether the oxygen heater control working incorrectly.

Deviations in the oxygen sensor ceramic temperature or the oxygen sensor not being operatively ready in a timely manner can lead to an increase in emissions above the applicable standards or prevent the sensor signal from being used as a diagnostic system monitoring device. Deviations may occur due to, for example, ageing of the heater element, defective wiring, increased heater circuit connector contact resistance, defective heater driver etc.

The enable conditions for the monitoring are

1. battery voltage above threshold
2. idle speed or part load
3. O2 sensor heater in operation
4. delay time for sensor warming up
5. no O2 sensor malfunction oxygen sensor heater circuit oxygen sensor electrical circuit

The diagnosis strategy is based on the detection via one of two methods, both cases being emissions relevant.

1. Heater Controller - Limit Check (P3026/3027) This part of the diagnosis is based on the monitoring of the Heater Controller. If under certain circumstances the regulation of the Heater Controller is at its limit stop continuously, it is assumed to have a malfunction. The diagnosis is carried out continuously.
2. Heater Diagnosis after engine start (P3026/3027) The internal resistance of the oxygen sensor has got to reach a fixed value after a certain period of engine running time. If this condition is not fulfilled the value of the internal resistance is not plausible an the sensor temperature is to low. The diagnosis is carried out once in every driving cycle.

Monitoring of electrical faults of the downstream sensors.

1. engine running
2. calculated catalyst temperature > threshold
3. battery > threshold
4. O2 sensor ready for operation
5. O2 sensor heater is active
6. closed loop upstream O2 sensor
7. no O2 sensor malfunction O2 sensor heater (downstream) O2 heating power (downstream)

The oxygen sensor electrical monitor detects the following malfunctions

No plausible voltages

1. ADC - voltages exceeding the maximum threshold VMAX are caused by a short circuit to Ubatt
2. ADC - voltages falling below the minimum threshold VMIN are caused by a short circuit of sensor signal or sensor ground to ECM ground

No plausible course of sensor voltage

An open circuit of the sensor upstream catalyst is detected if the ADC - voltage is remaining in a specified range after the sensor has been heated.

Scheme 271

The purpose of this monitor is to detect errors within the O2 Sensor Heater Circuit. The signal for the O2 sensor heater is pulse-width modulated. The signal of the powerstage is monitored internally by the driver.

1. battery voltage not too low

The driver can distinguish between three symptoms

1. HO2S Down SCVB
2. HO2S Down SCG
3. HO2S Down Open Line

If one of the above mentioned symptoms is present, a malfunction is detected and the corresponding fault code is stored.

In order for the oxygen sensor to function properly, the sensor element must be heated. A non-functional heater delays the sensor readiness for closed loop control and influences emissions.

1. battery voltage above threshold
2. O2 sensor heater in operation
3. delay time for sensor warming up
4. no O2 sensor malfunction oxygen sensor heater circuit

The monitoring function measures continuously both the sensor heater current as well as the heater voltage (heater supply voltage) to calculate the sensor heater resistance.

The monitoring strategy is based on the comparison of the O2 sensor heater resistance to a calibrated threshold. If the heater resistance fall below or exceeds the threshold, an O2 sensor heater malfunction is detected.

Scheme 272

Plausibility Check

The plausibility/rationality check of the post - catalyst oxygen sensor covers three diagnostic strategies

1. Diagnostic during fuel cut off, too verify if the signal is below a certain threshold while in fuel cut off (P0139/0159)
2. Diagnostic while re-injection, too verify if the signal climbs above a certain threshold after re-injection (P1130/1131)
3. Diagnostic during wide open throttle, too verify if the signal climbs above a certain threshold in WOT (P0136/0156)

Active Test

Futhermore, an active test is performed which is the response on a fuel trim Malfunction.

The monitor will only be enabled if a fuel correction fault has been detected and a malfunction code has been stored, i.e., P2096/2098 or P2097/2099.

If a fuel correction malfunction exists, this diagnosis will be enabled to determine if the root cause of the malfunction is due to a stuck signal of the Upstream O2 sensor or a system malfunction, i.e. vacuum leak, injector, etc... If it has been determined that the O2 signal was the root cause of the fuel correction fault, the appropriate DTC will be stored along with the fuel correction DTC.

Rear sensor signal too lean - P2270/2272

The lambda is rich and rear sensor signal lean - O2 sensor signal is under rich voltage limit

Rear sensor signal too rich - P2271/2273

The lambda is lean and rear sensor signal rich - O2 sensor signal is over lean voltage limit

1. battery voltage above threshold
2. O2 sensor heater in operation
3. delay time for sensor warming up
4. engine speed
5. engine load
6. engine coolant
7. no O2 sensor malfunction oxygen sensor heater circuit

Plausibility Check - Monitoring from rich to lean intake mixture

The sensor voltage during lean operation is used to monitor the sensor's activity. Therefore this check is performed during a deceleration fuel cut-off event.

The diagnosis starts after a calculated air mass (integral) is reached at transient from any operation mode to the fuel cut-off mode and with a defined time in deceleration fuel cut-off.

The sensor voltage has to drop below a pre-determined value/threshold otherwise a fault is detected and a code is stored.

When the conditions at deceleration fuel cut-off are such that the rich to lean monitor cannot complete, an additional monitor from lean to rich intake mixture will be started according to the following section.

Plausibility Check - Monitoring from lean to rich intake mixture

The sensor signal is monitored immediately after the transition from fuel cut-off to normal fueling (re-injection). For a positive diagnostic result the signal must overrun a threshold and a certain amount of air mass flow has to be reached. To ensure this lean to rich diagnosis, a short-term fuel enrichment will be performed if necessary.

Plausibility Check - Monitoring at WOT (wide open throttle)

An additional diagnostic in "wide open throttle" engine conditions is performed. The purpose is to validate a lean stuck signal under high load conditions.

The diagnosis starts after a calculated time in WOT conditions has reached and the lambda value of the pre- catalyst O2 -sensor is below a calibrated threshold.

Outline of the SAS diagnosis strategy

In order to ensure the functionality of the secondary air system (SAS), a check of pump (SAP), secondary air valves and hoses is performed. It uses a secondary air flow meter (SAFM) to verify the amount of secondary airflow through the system and the oxygen sensors in order to allocate the malfunctioning engine side of the SAS.

Conditions for diagnosis

1. No malfunction in engine temperature
2. No malfunction in oxygen sensors
3. No malfunction in ambient pressure
4. No malfunction in ambient temperature
5. No malfunction in engine-off timer
6. SAP active
7. engine running inside an RPM- and load- frame
8. air mass flow inside a frame
9. cylinder fill inside a frame
10. fuel cut-off time shorter than threshold
11. battery voltage higher than threshold

Description of minimum air flow check

Once the proper operation of SAFM and the SAP is confirmed in the first two sections of the diagnosis, this check tests the tightness and the minimum airflow of the SAS by the use of the SAFM and the oxygen sensors in the exhaust system. The amount of secondary air flow (SAF) is compared to a secondary airflow model. Once the SAF falls considerably below the model a minimum airflow is detected.

The signals of the oxygen sensors are adjacent compared in order to detect the location of malfunction in the main- or the bank-selective part of the SLS-hosing or Valves. In case one bank is detected much richer than the other, this side can be detected as defective, since it gets less SAF. If the signals are approximately even, the fault is in the main part of the SAS.

Description of leak check

The leak check operates very similar to the minimum air flow check with the only difference, that a leak is detected in case the flow exceeds the secondary airflow model considerably. The bank allocation is identical.

Additional lambda comparison

In borderline cases, where e.g. one SAS-side is partly blocked and the flow loss is compensated by a high tolerance system, the air flow checks may not detect hundred per cent accurately. Therefore an additional lambda comparison is used which works similar to the bank allocation described above. If one bank is detected much richer than the other, it is detected as faulty. The decision for leak or plugging is reached by the comparison of SAF and model, whereas "model higher than flow" means plugging and vice versa.

Closed Loop Lambda Control - Enable Conditions

Closed loop lambda control is enabled (with a delay) at the start of a driving cycle and can be temporarily or permanently deactivated during the driving cycle. The turn-on delay at start of a driving cycle is described by the following enable conditions

1. the upstream oxygen sensor operability is detected i.e. the upstream HO2'S operating temperature has been reached
2. certain time after engine start has expired
3. Closed loop lambda operation is disabled, if the following conditions are met: when catalyst overheating prevention is active sensor heater failure present in the current d.c. sensor failure present in the current d.c. misfire detected in the current d.c. the purge valve plausibility check is active secondary air system is active

The diagnostic strategy is set up in different parts

1. electrical diagnostic
2. gradient diagnostic
3. plausibility check / sensor stuck

It is to mention that no time to closed loop diagnostic is performed! The closed loop time for the lambda controller depending on the coolant signal is not used anymore.

Electrical diagnostic of engine coolant temperature

The purpose of this diagnosis is to detect electrical faults of the sensor signal. The Input signal is analog from a NTC and has to be in a calibrateable range. Short cut to ground can be detected immediately, short cut to voltage battery or open load. If an error symptom is detected, the error counter is debounced.

1. ignition key on

Error Symptoms

1. Short circuit to voltage battery
2. Short circuit to ground

The purpose of this diagnosis is to detect an implausible gradient on the coolant temperature signal. The diagnostic function checks whether the difference between one measured coolant temperature value and the succeeding value is too big.

1. Engine running

Error Symptom

1. ECT signal gradient error

Input parameters for monitoring

1. measured ECT

The purpose of this diagnosis is to detect a stuck coolant temperature signal. The diagnostic function checks after the coolant model has increase a certain amount of deg C, also the measured signal of the ECT has increased a calibrated amount.

1. engine running
2. driving cycle conditions
3. no electrical ECT error present
4. time in fuel cut off
5. accumulated air mass while driving cycle (to prevent false code while extended idle conditions)

1. ECT signal stuck error

1. measured ECT
2. calculated ECT

Scheme 273

This figure represents the proper working coolant system system. The coolant sensor is not stuck.

Scheme 274

This figure represents the none proper working coolant system system. The coolant sensor is stuck at 30 deg C.

Description of the curves

The ECT does not increase the temperature. The coolant temperature model increases like expected. At a certain time a malfunction for a stuck sensor is set and the coolant model temperature is used as reference for the coolant temperature.

The BMW-engines have a common cooling system with an Engine Coolant Temperature (ECT) and a Radiator Outlet Temperature (ROT) Sensor. Furthermore a mechanical thermostat is a part of this system. The temperature movement of the ROT- Sensor validates the proper function of the thermostat, as described more detailed on the following pages.

1. No DTC's relevant to the coolant system

Scheme 275

This figure represents the proper working system (thermostat opens and closes as expected)

Description of the curves

The ECT and the coolant temperature model increases until the operating temperature is reached. The thermostat is working properly.

Scheme 276

This (Scheme 255) represents the malfunction-case of the system (thermostat is stuck open)

Due to the thermostat is stuck open ("stuck open" means, that the thermostat is not closed regular and a smallest opening leads to the same result as a fully open thermostat since there are no intermediate conditions), the engine coolant temperature (ECT) rises but does not reach the thermostat regulating temperature.

The coolant temperature model increases as expected without malfunction. The difference in-between the model and the measured sensor temperature is the criteria to set a malfunction.

As a result a fault code P0128 will be stored in the ECU.

The purpose of this diagnosis is to detect electrical faults as defined in OBDII requirements. The input signal is analog from a NTC and has to be in a calibrated range. Short cut to ground can be detected immediately, short cut to voltage battery or open load after a delay time. If an error symptom is detected, the error counter is debounced.

1. ignition key on

1. Short circuit to voltage battery
2. Short circuit to ground

The plausibility check of the IAT compare the temperature of bank 1 and bank 2. As soon as the difference in-between bank1 and bank2 becomes too high, a malfunction for the suspected sensor (bank) will be set. To define which sensor is not functioning properly a intake air temperature model is used for.

1. engine running
2. vehicle speed above threshold for certain time
3. engine coolant above threshold
4. no error of electrical ECT diagnosis
5. no error of ECT gradient diagnosis
6. no error of ECT stuck diagnosis
7. no error of electrical IAT diagnosis

1. signal not plausible

1. ECT
2. Intake air temperature bank 1 and bank2
3. vehicle speed
4. time
5. engine load
6. engine running at part load

Variable Camshaft (VANOS)

The variable camshaft controls the position of the camshaft in relation to crankshaft. The actuator used for to vary its position is a high-pressure hydraulic motor controlled by one 3/2-way-hydraulic valve.

The testing of the Variable Camshaft consists of

1. An electrical diagnostic of the control valve driver circuit
2. A high-pressure test
3. A rationality check between target and measured position
4. A rationality check of the max. reachable position.

A smart high side driver performs the testing. It compares the driver's current trough on-condition with a lower limit, to detect open load. An overload or a short to ground is detected by over current or an overheating shut down. In off-condition the voltage level is compared with a max. limit to detect a short to battery.

1. battery voltage

The pressure test runs after each engine start.

The control valves of the inlet camshaft are activated in such a manner that it should move in the opposite direction, with respect to its direction of rotation. If no sufficient change in the opposite direction is detected, within a temperature dependent time, a fault code is stored.

1. engine status: running

When pressure condition is detected, the position regulator for each camshaft is activated.

Afterwards, the difference between target position and the measured position is calculated for each position measurement and is filtered with a low pass filter.

If the filtered difference exceeds a positive threshold, a fault code "position retarded" is stored.

If the filtered difference is below a negative threshold, a fault code "position advanced" is stored.

1. engine status: running
2. engine running time
3. variable camshaft regulation active
4. pressure detected

When the target position is next to the expected max. mechanical limit, the VANOS is driven toward its mechanical limit.

After a short time, when the position has settled, this position is stored as the max. mechanical limit.

This position is compared to the expected limit, and if the difference is to large, a fault code is stored.

1. Engine status: running
2. Engine running time
3. Pressure detected
4. Target position next to max. mechanical limit

Each camshaft (CAM) has a tooth wheel with six teeth. The sensor converts each tooth to a signal with a rising and falling edge. Each falling edge of the camshaft sensor (oncoming tooth) is a signal for the CAM position relative to crankshaft.

The inlet CAM's have a periodical tooth's spacing with 6 times 60°angle to measure the camshaft position.

The outlet CAM's has an additional function

1. Synchronize the crankshaft with the CAM.

So, the outlet CAM's have a different angle for each tooth.

To synchronize the crankshaft with the CAM, after the missing teeth of the crankshaft the level of the CAM senor (high or low) signs the right synchronization.

A plausibility diagnosis is performed that compares the outlet CAM sensor level after each missing tooth of the crankshaft. The CAM sensor must different levels after each complete crankshaft revolution. If not, a CAM synchronization error is stored.

If a CAM synchronization error is detected, the synchronization is made with the ion current signal

The ignition is switched to 360° mode. The ion current is also measured every 360° for each cylinder. But combustion occurs only every 720° and is detected with the ion current. So the CAM synchronization can be determined.

There is an additional plausibility check for each CAM sensor

The number of teeth for two complete crankshaft revolutions is counted. If there are too much or too less tooth's, a sensor error is stored.

If so, the CAM's position can't be measured correctly and all CAM's are positioned at their save positions.

See the summary table for further explanation of this monitor.

Crankshaft Sensor

The detection of the crankshaft signal is continuously monitored and distinct in four different possible errors.

Failed Start Attempt

During the attempt to start the engine the crankshaft revs and both camshaft revs are monitored. If for a certain time the engine revs remains zero, whereas any of the two camshafts revs reaches an appropriate level, a missing crankshaft signal is detected.

Top-Out

Top-out of the crankshaft signal is monitored during normal engine operation over certain revs. If several sudden top-outs occur within a time constrained a loose or spuriously faulty crankshaft signal is detected.

Short to Battery

The crankshaft signal is continuously electrically monitored even during engine stand still. An error will be detected when one or both of the differential crankshaft signals are short-circuit the power supply.

Short to Ground

The crankshaft signal is continuously electrically monitored even during engine stand still. An error will be detected when one or both of the differential crankshaft signals are short-circuit to ground.

Actuators that can affect emissions are monitored by power stage voltage check for valid signals.

Continuous Monitoring if

1. Ignition key on
2. battery voltage > threshold

Invalid actuator output signals at power stage are regarded as circuit malfunctions shorted to BATT, GND or Open circuit.

The rationality check of the system is divided into two sections.

Firstly, the engine-control-unit (ECU) stores the relative time information when the engine is stopped. At restart the difference to the current relative time is used to evaluate the time, the engine has been off. This engine-off-time is checked against the dropping time of engine coolant temperature (ECT)

Secondly, the independent timer of the ECU is compared to the relative time measurement to see if they are synchronized.

1. no malfunction of engine temperature
2. no CAN-timeout for telegrams sent by instrument-cluster
3. no restart after ECU reset
4. no low battery voltage with engine running
5. no stalled engine
6. coolant temperature at engine stop
7. coolant temperature at start

Monitoring Function: Dormant time rationality check

The engine cools down during engine-off-time. The diagnosis uses this characteristic to verify the engine-off-timer measurement.

If the engine is stopped in warm conditions a maximum coolant temperature drop-speed is possible. An engine-off time measurement with a too fast cooling time, shorter than time_min, is irrational.

If the engine temperature has been greater than a threshold at stop and is still greater than another threshold at restart (before entering steady conditions), the engine cannot be off for longer than a certain time time_max.

If the engine-off-timer diverges from the range between time_min an time_max the relative timer is faulty and an error is detected.

Scheme 277

Monitoring Function: Monitoring during engine operation

As the ECU has its own time measurement, it can be used to verify the relative-time-measurement, whilst engine is in operation.

If the engine has been running for an operating-time time-ml, the relative-time-measurement has to have increased by the same amount of time since engine-start. If this is not the case, a fault will be set.

The idle speed controller is responsible for the correct idle speed. According to the legal requirements a plausibility check is performed.

1. engine status: idle
2. coolant temperature
3. vehicle speed

If the desired idle rotational speed exceeds a defined limit for a certain time, the error code "engine speed too high" (P0507) is generated.

If the rotation is below a defined limit for a certain time the error code "engine speed too low" (P0506) is generated.

Idle Throttle Valve Actuator

There are two independent throttle valve actuators (LLS1, LLS2) for each cylinder bank.

The ECH is communicating via CAN-Bus.

Scheme 278

The Communication between LLS1, LLS2 and the ECH is monitored all the time. These checks are implemented: Timeout (U0136, U0146), Alive (U0137, U0147), Checksum and ECU-intern fault (U0138, U0148).

If it is not possible to start a communication between at least one of the LLS after 10 times, the fault codes P154B is set.

If there is an electronic-problem (short between can-high and can-low) the CAN-controller detects a Bus-Off by himself (U1139).

1. KL15 on
2. KL87 on

Each time the actuator is active, several checks are continually performed

Diagnostic Status

The actuator checks i.e. RAM, ROM, Actuator-Status or overheat by himself. If there is an error, he transmits it by CAN. The ECH is then generating the error codes "Diagnose status - System" (P158B, P159B" or "Diagnosestatus - Regler" (P158D, P159D).

Actuator-Mode

The actuator changes his mode to "Failsafe" the error code "Return mode auf Failsafe" (P158A, P159A) is generated.

If the return-mode is different to the internal mode, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code " berwachung Modevorgabe" (P152F, P153F) is generated.

Position

If the actuator sends the fault-indication instead of the target position, the fault code "Istwert fehlerhaft" (P152D, P153D) is generated.

If the measured position is retarded in relation to the target position, exceeding a certain threshold, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code "Soll/Istvergleich" (P152E, P153E) is generated.

Target-Position

If the return-target-position is retarded in relation to the target position, exceeding a certain threshold, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code "Sollvergleich" (P152C, P153C) is generated.

1. KL15 on
2. KL87 on
3. No Communication-Fault
4. Actuator is active

Every 10 min the actuator do a shelf-calibration of the 100%-position. If the LLS responds with a fault-adaptations, the error code "Adaption fehlerhaft" (P158C, P159C) is generated.

1. KL15 on
2. KL87 on
3. No Communication-Fault
4. Actuator is active
5. Throttle valve position greater 15%

Throttle Position Sensor (Butterfly Valve)

The butterfly valve position is measured using two independent double sensors.

Sensor 1 is the main sensor for the actuator.

Sensor 2 is for controlling the throttle position in the ECU.

Scheme 279

The acceptable voltage range of both sensors is continually monitored. If the voltage is outside the acceptable range, then a P-Code is stored and "check engine soon" indicator bit is set.

1. ECU active

Rationality check

1. KL87 on
2. No Communication-Error

Scheme 280

First the voltage range of both sensors is checked. If they are under or over a certain voltage, the corresponded fault code is set.

If the voltage falls remains between the Min / Max value (meaning there are no errors), then a rationality check is performed. This means, that Sensor 1 + 2 of each bank must measure approx. the same butterfly valve position. If this is not the case, then a P-Code is stored and the "check engine light" indicator bit is set.

Throttle Valve Actuator

There are two independent throttle valve actuators (EDR1, EDR2) for each cylinder bank. The ECH is communicating via CAN-Bus and two additional signals "Enable-Steuerung" to disable the actuators.

Scheme 281

The Communication between EDR1, EDR2 and the ECH is monitored all the time. These checks are implemented: Timeout (U0141, U0151), Alive (U0142, U0152), Checksum and ECU-intern fault (U0143, U0153).

If it is not possible to start a communication between at least one of the EDR after 10 times, the fault codes P153B is set.

If there is an electronic-problem (short between can-high and can-low) the CAN-controller detects a Bus-Off by himself (UC140).

1. KL15 on
2. KL87 on

Each time the ECH is powered on, a pre-drive check of the throttle valve system is performed.

Positioning of the throttle valve

The first test is a rationality check of the control loop: A target position is set and the reaction of the position sensor is checked.

If the position is not within the target position tolerance, a fault code "Gest ngetest" (P1628, P161F) is generated.

Adaptation

The next step is the adaptation of the Zero-Position. After the adaptation is done, the value is checked by the following tests

1. Actuator detected an error: generate false code P0123, P0223
2. Signal range is too high: generate false code P0121, P0221
3. Value out of range, if not false code P0122, P0222

Safety Switch Off

The third test is a verification of the safety switch of by the supervisor processor: Before activation of the main processor, the supervisor processor switches off the actuator. If the throttle valve is opening, the error code "Enable-Leitung fehlerhaft" (P1628, P161F) is generated.

Additional the Safety Switch Off is electrically checked all the time. The following errors could detected by the hardware: "Short to GND" (P156D, P157D), "Short to UB" (P156E, P157E) and "Openload" (P156F, P157F).

1. KL15 on
2. KL87 on
3. No Communication-Fault

Each time the actuator is active, several checks are continually performed

Diagnostic Status

The actuator checks i.e. RAM, ROM, Actuator-Status or overheat by himself. If there is an error, he transmits it by CAN. The ECH is then generating the error codes "Diagnosestatus - System" (P0638, P0639" or "Diagnosestatus - Regler" (P1630, P1636).

Actuator-Mode

The actuator changes his mode to "Failsafe" the error code "Returnmode auf Failsafe" (P1630, P1636) is generated.

If the return-mode is different to the internal mode, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code " berwachung Modevorgabe" (P154F, P155F) is generated.

Position

If the measured position is retarded in relation to the target position, exceeding a certain threshold, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code "Soll-/Istvergleich" (P154E, P155E) is generated.

Target-Position

If the return-target-position is retarded in relation to the target position, exceeding a certain threshold, a timer is started. Otherwise the timer is cleared. If the timer exceeds a maximum time, a fault code "Sollvergleich" (P154C, P155C) is generated.

1. KL15 on
2. KL87 on
3. No Communication-Fault
4. Actuator is active

After KL15 turned off, the springs of the system are tested: the actuator opens the throttle to 15% and switch off. If the throttle position is close after a certain time, no fault code is set. Otherwise the codes "Fehler durch Satellit" (P1634, P161D) or "Timeout" (P1631, P161E) are generated.

1. KL15 off
2. KL87 on
3. No Fault

Accelerator Pedal Position Sensor

The pedal position is determined using two independent sensors with two independent voltage supplies.

Scheme 282

The acceptable voltage range of both sensors is continually monitored. If the voltage is outside the acceptable range, then a P-Code is stored and "check engine soon" indicator bit is set.

1. ECU active

Scheme 283

First the voltage range of both sensors is checked. If they are under or over a certain voltage, the corresponded fault code is set.

Once the Min / Max voltage range has been checked (meaning they are no errors), they are checked for rationality. This means both sensors must measure approximately the same pedal position value. If this is not the case, a P-Code is stored and the "check engine soon" indicator bit is set.

Each recognized error leads to a power reduction.

Each detected error leads to a power reduction. Full power is no longer possible until the driver restarts the motor.

To support a sufficient vacuum in the brake booster under all conditions, a vacuum pump is installed at the brake booster. The pump is controlled by a vacuum sensor.

If the sensor or the vacuum pump is malfunctioning, catalyst heating is disabled and cyl 6-10 are deactivated to ensure an error-free operation of the brake system.

In this case the engine emissions are affected.

As the brake booster vacuum pump is energized by a relay, the electrical diagnostics is limited to the relay.

In addition to that the vacuum pump delivery rate is evaluated every time when the monitoring conditions are met.

1. Intake manifold vacuum low (<50mbar, =>high engine load)
2. Vacuum pump running
3. No brake activity
4. no malfunctions of: intake air temp. sensor ambient pressure sensor

When the vacuum pump relay is energized and all monitoring conditions are met, the pressure sensor signal is delivered and the calculated pressure decline is compared to a threshold. If the pressure decline is lower than the threshold for more than 0.5sec, a pump error is set.

To support a sufficient vacuum in the brake booster under all conditions, a vacuum pump is installed at the brake booster. The pump is controlled by a vacuum sensor.

If the sensor or the vacuum pump is malfunctioning, catalyst heating is disabled and cyl 6-10 are deactivated to ensure an error-free operation of the brake system.

In this case the engine emissions are affected.

Apart from the electrical diagnostics (short to batt, short to ground, open load) the brake booster vacuum sensor monitoring looks for permanent deviations of the measured value from a calculated value to detect a sensor drift.

When the difference exceeds an threshold (200mbar) for a certain time (<60sec), the vacuum sensor malfunction code is set.

1. Engine running at idle or deceleration fuel cutoff
2. No catalyst heating
3. No brake activity
4. no malfunctions of: intake air temp. sensor ambient pressure sensor CAN-bus

When the engine is running, the pressure inside the brake booster is permanently calculated depending on ambient air pressure, intake air temperature, intake manifold pressure, engine load, engine speed and engine coolant temperature.

The difference between calculated and measured pressure in the brake booster is filtered with a low pass filter with a response time of 60 sec..

When the monitoring conditions are not met, the filter is stopped.

If the filtered deviation between calculated and measured pressure exceeds 200mbar, a brake booster vacuum sensor error is set.

The required air intake is determined by using a Hot-film Mass-Air Meter (HFM). The HFM measures the mass of the air flowing through, producing an analog voltage signal between 0V and 5V.

Electrical diagnostic air meter

1. engine running
2. battery voltage
3. no malfunction

Signal range check of mass air flow signal

The monitoring of the engine load sensor consists of a signal range check. It compares the sensor signal with an upper and lower threshold to detect short circuit.

If the measured value from the mass air flow sensor exceeds the upper calibration threshold; a short circuit to battery is detected and a maximum fault is set.

If the measured value from the mass air flow sensor exceeds the lower threshold; a short circuit to ground is detected and a minimum fault is set.

The rationality check of the Air Mass Flow Meter, is a comparison of three air mass signals.

1. the air mass (measured through the air meter)
2. the air mass calculated out of the throttle flap position and
3. the calculated air mass out of the measure WRAF- sensor signal

1. No fault of crankshaft position acquisition
2. No fault of throttle position acquisition
3. No fault of intake air temperature acquisition
4. No fault of coolant temperature acquisition
5. No fuel cut off
6. No WRAF sensor failure
7. No fault of MAF sensor circuit continuity check
8. Time after start must exceed minimum threshold
9. Engine speed between MIN/MAX-threshold
10. Limited dynamics engine speed and engine load
11. Battery-Voltage exceeding MIN-threshold
12. Coolant temperature exceeding MIN-threshold
13. Engine load signal between MIN/MAX-threshold

The ambient-pressure-sensor is monitored continuously in a 100ms-grid with two kinds of diagnostics

1. Electrical diagnostics It compares the sensor signal voltage with an upper and lower limit to detect short circuit.
2. Pressure Plausibility Electrical failures or influences due to components can generate a malfunction of the ambient-pressure-sensor. A stuck sensor is, for instance, permanently emitting the same value. This kind of error cannot be recorded by the conventional electrical diagnostics, as well as a sensor drift inside the frame of electrical thresholds. Therefore the signal of the ambient-pressure-sensor is additionally checked in comparison to a model.

no malfunction in

1. ambient pressure sensor
2. driving speed signal
3. Mass Air Flow Sensor
4. Mass Air Flow Sensor Plausibility
5. Intake Air Temperature Sensor
6. Crankshaft Position Sensor
7. Throttle Position Sensor
8. Pedal Position Sensor
9. Camshaft Position Sensor
10. idle throttle valve
11. engine status: running
12. vehicle speed inside a frame
13. intake air temperature inside temperature frame
14. engine speed inside engine speed frame
15. ambient temperature inside temperature frame
16. throttle position inside a frame
17. throttle valves adjusted
18. idle throttle valves adjusted
19. camshaft adjusted engine load calc. via mass air sensor and throttle valve position

Monitoring Function: Electrical diagnostics of ambient pressure sensor

If the measured value from the ambient-pressure-sensor exceeds the upper calibration threshold, a short circuit to battery is detected and a maximum fault is set.

If the measured value from the ambient-pressure-sensor undershoots the lower threshold, a short circuit to ground is detected and a minimum fault is set.

Monitoring Function: Rationality check of ambient pressure sensor

Since the maximum rational pressure drop/rise is limited by the utmost decline/pitch at maximum vehicle speed or abruptly changing meteorological conditions, every gradient beyond this plausible threshold is detected as fault and the rationality check is stopped for this driving cycle.

(In case the sensor drift exceeds the electrical thresholds furthermore, an additional electrical error is detected.)

Since the sensor can be stuck at a wrong value (inside the electrical frame) after an implausible drift and an additional, repeated drift is not very likely, the fault path is not cleared before an additional model has proven the accuracy of the signal in one of the proximate DCs.

An incorrect comparison of the ambient pressure model in the subsequent driving cycle confirms the preceding error as well as a repeated but unlike excessive gradient does again.

If the sensor operates on an incorrect level without having had an excessive gradient before, this is also detected by a comparison with the aforementioned ambient pressure model.

An unobjectionable operating sensor is also detected by the ambient pressure model, which leads to the clearance of the fault path.

The engine control units of M Automobiles consist of a three-processor system. One is a Digital-Signal-Processor (DSP) and has the main function of detection knocking Signals. The other two are RISC Processor from the Motorola Power PC family. The main functions of each are described below.

Power PCI(INJ): Injection timing, fuel-mixture generation, calculation of engine load, monitoring of PPC2

Power PC2(IGN): Ignition timing, controlling throttle, monitoring of PPC1

In order to monitor the ECU hardware, the following monitoring functions are implemented

1. Memory Tests
2. Processor Communication Monitoring
3. Watchdog Monitoring
4. Reset Monitoring
5. Analog/Digital Converter Monitoring
6. CPU-Tests

Memory Tests

All of the processors have the capability to check the memory.

Internal memory test will made continuously. All internal RAM will be written by special test pattern, an restored after checking. If checking failed 'SG interner Fehler' - 'RAM Fehler' (P0604) will generated.

ROM Tests

All of the ROM(FLASH) of each processor will also be checked over multiple CRC's continuously.

If an error occurs, the error 'SG interner Fehler' - 'ROM Fehler' (P0605) is generated.

Test Non-Volatile data memory

After each restart, the ECU'S non-volatile data, consisting of adaptation data and error storage, is stored in flash memory and protected using a checksum.

During the control initialization phase the data is read from memory and check according to the checksum. If the checksum fails, the last 'good' non-volatile data's will be used.

Processor Communication Monitoring

Each processor checks, if the critical functions are calling periodically. Secondly all the task are checked, if they are called every time. The last check is the communication between the two Power PCs. If one of the errors occur, the fault code "SG interner Fehler Prozessorkontrolle" (P060A) is set.

Analog/Digital Converter Monitoring

The system checks continuously the conversion of the pedal values (pwg) on both processors. If it is different for a several time, the fault code "SG interner Fehler - unplausibel" (P0606) is set.

The torque request is calculated from the pedal-value and the minimum and the maximum torque. If a DSC- or SMG-Request is active, the torque request is from them.

The actual engine torque is calculated from the mass airflow.

To avoid critical situations, the torque request and the engine torque is checked.

1. KI15 on
2. Engine running over 500Upm

There are a different kind of diagnostic function running on the engine control unit

1. Monitoring of the minimum torque: If the minimum torque is over 60Nm and the engine speed is over 1500Upm, or the torque losses are positive, the fault code "Minimalmomednt unplausibel" (P16B8) is set.
2. If the Torque request exceeds the Limit, the fault code "Sollmoment unplausibel" (P16B7) is set.
3. If the actual engine torque is over the torque request (of the driver, DSC or SMG) for a certain time or the pedal-value is zero and the throttle position exceeds the limit, the fault code "Soll-/Istvergleich" (P16C1) is set.
4. If the integration part of the idle speed controller exceeds the limit, the fault code "LLR- berwachung" (P16B1) is set.

To avoid critical situations there are several function to check the correct work of the ECU. One part of the safety concept is the Level 2.

1. Ub > 9V
2. Engine running

Checking of Fuel Cut Off-Checking

If the engine speed is over the maximum engine speed, the system checks the status of the injections valves. If they are not switched of, the fault code "SG intern Ueberwachung Ebene 2 - Drehzahlbegrenzer" (P1691) is generated.

Engineload

The Level2 calculates an own engineload from different input signals to the level 1. If an inconsistence is occurred for a certain time, the fault code "SG intern Ueberwachung Ebene 2 - Sensorik" (P1688) is set.

Engine Speed

Both processors calculate the engine speed. If there is a difference for a certain time between them, the fault code "SG intern Ueberwachung Ebene 2 - Sensorik" (P1681) is set.

Torque Request

The calculation of the torque request and the actual engine torque is done in the level 2 a second time. If there are too big difference between the two levels of the following variables, the fault code "SG intern Ueberwachung Ebene 2 - Momentenmanager" (P1689) is set

1. Minimum torque
2. Maximum torque
3. Torque losses
4. Relative drivers choice

At least the torque request is compared with the actual level2-torque. If the difference exceeds the limit for a certain time, the fault code is set as well.

External Torque Request

The external torque request from the SMG is recalculated in the level 2. If there are an error inconsistence of the request status, the gearbox speed or the gear information, the fault code "SG intern Ueberwachung Ebene 2 - Eingriffe" (P16B3) is generated.

CPU-Test

All the used arithmetic functions, interpolation routines and filters are checked continuously of both processors. If the calculated results are different, they calculate the same test again. If it is different a second time, the fault code "SG intern Ueberwachung Ebene 2 - Systemfehler" (P1602) is generated.

A second way to check the processor is to store critical variables with there complement. If they are inconsistent, the fault code is set as well.

Test of the Errorhandler

The errorhandler is checked periodically: First the error is active, then the error is not active. If all mechanism are working correct, the error is not in the Errorlist, but if he is, the fault code "Fehlerspeichertest" (P1606) is generated.

One part of the Sequential Gearbox is running in the engine control unit. For the Communication between the SMG and the ECU a CAN is used. To avoid critical situations, several checks are running on the ECU.

1. Ub > 9V
2. Bus active
3. Engine running (only safety checks)

Communication

The Communication is checked continuously. If no message is received after a certain time, a timeout (U114B, U114E, U115B) is detected. If a message is received, the Alivecounter must be different to the last message, else the fault codes U114A, U114D or U115A are set. Next a checksum is calculated and is compared to the received checksum: they must be equal, else the errors U114C, U114F or U115C are detected.

If there is an electronic-problem (short between can-high and can-low) the CAN-controller detects a Bus-Off by himself (UC140).

Safety Checks

Additional to the communication-check the ECU checks the critical receive-signals from the gearbox

1. Gearbox speed If the gearbox speed exceeds the limit, or is not plausible to the engine speed, an error is detected.
2. Target gearbox speed If the target gearbox speed exceeds the limit, or is not plausible to the engine speed, an error is detected
3. Clutch torque: The clutch torque and the sate of the clutch must be consistence

The fault code is P0700.

The internal calculated gearbox speed (from gear info and wheel speed) is checked as well. If there is an inconsistence to the engine speed, the fault code P1670 is set.

Calculated load

The calculated engine load "LOAD_CLC [%]" is based on the measured mass air flow (metered by the h ot- f ilm air- m ass sensor (HFM)).

Strategy

A 2-dimensional map is used to interpolate the calculated engine load "LOAD_CLC [%]" depending on metered mass air flow and engine speed. A weighting factor is applied to compensate the altitude influence.

The calculation is performed as follows

LOAD_CLC [%] = LOAD_CLC_RAW f (metered mass air flow, engine speed)

x (1013hPa / ambient pressure) x 100%

with

CALCULATION CHART

In case of a malfunction of the HFM, the metered mass air flow is substituted by a modeled mass air flow value.

See also:
• P2096 / P2098, P2097 / P2099, P114A / P114C, P114B / P114D
• P2243, P2247, P112C, P112D, P2626, P2629
• P154B, U0136, U0146, U0137, U0147, U0138, U0148, U1139, P152C, P153C, P152D, P153D, P152E, P153E, P152F, P153F, P158A, P159A, P158B, P159B, P158C, P159C, P158D, P159D
• P0121, P0221, P0123, P0223, P0638, P0639, P1630, P1634, P161D, P1631, P161E, P1636, P153B, P154C, P155C, P154E, P155E, P154F, P155F, P156D, P157D, P156E, P157E, P156F, P157F, FP1628, P161F, U0141, U0151, U0142, U0152, U0143, U0153, UC140
• P1691
• P1688
• P1681
• P1689
• P16B3
• P1602
• P1606