Self Diagnosis - Theory & Operation: Other BMW 3 series E90/E91/E92/E93

Catalyst Monitoring

Note. OBD System Description of Siemens VDO ECU MSV80 for following models: X3 3.0i, X3 3.0Si, 323i (only Canada), 328i, 328xi, 328Ci, 328Cxi, 328i sport wagon, 328xi sport wagon and 328Ci convertible

P0420/0430

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 sign 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.

Variables List

VARIABLES LIST

Misfire Monitoring

P0300, 0301, 0302, 0303, 0304, 0305, 0306

The method of engine misfire detection is based on evaluating the engine speed fluctuations.

The engine torque is a function of engine speed, engine load and the moment of inertia.

In order to detect misfiring at any cylinder, the torque of each cylinder is evaluated by metering the time between two ignition events, which is a measure for the mean value of the speed of this angular segment. This means, a change of the engine torque results in a change of the engine speed.

It is also an influence of the load torque. This means, the influences of different road surface, e. g. pavement, pot holes etc. If the mean engine speed is measured, influences caused by road surfaces have to be eliminated.

This method consists of following main parts

Data acquisition

The duration of the crankshaft segments is measured continuously for every combustion cycle.

Sensor wheel adaptation

Within a defined engine speed range and during fuel cut-off, the adaptation of the sensor wheel tolerances, instead of the misfire detection, is carried out.

With progressing adaptation the sensitivity of the misfire detection is increasing. The adaptation values are stored and taken into consideration for the calculation of the engine roughness.

Calculation of the engine roughness

The engine roughness is derived from the differences of the segment durations. Different statistical methods are used to distinguish between normal changes of the segment duration and the changes due to misfiring.

Determination of misfiring

Misfire detection is performed by comparing the engine roughness threshold value with the engine roughness value. If the threshold is exceeded, single misfire is detected.

Statistics, Fault processing

Emission Limit: (e) (3.2.2)

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.

Catalyst Damage: (e) (3.2.1)

If the weighted sum of cylinder(s) misfire counters within 200 revolutions exceeds a predetermined value the fault code for catalyst damage relevant misfiring is stored and the cylinder with the highest rate will be switched off and the MIL will be switched on immediately. If two cylinders are switched off and the misfire rate is still above the damage limits, MIL is flashed immediately. If one of the cylinder selective counters exceeds the predetermined threshold, the following measures take place

1. The Lambda closed loop system is switched to open-loop condition.
2. The cylinder individual fault code is stored or if multiple cylinders, then the Global fault code is set.
3. Fuel supply of the misfiring cylinder(s) is not cut-off (per customer request)
4. No downstream fuel trim.

All misfire counters are reset after each interval.

Function Variables

FUNCTION VARIABLES

Evaporative system leak measurement

P0442/0456, 1434, 1447, 1448, 1449

EVAP (Functional check canister purge solenoid)

P0440, 0441

Monitoring the canister purge solenoid

The diagnosis is used for the functional test of the CP solenoid (CPS).

The test consists of three steps. Step 2 can be triggered separately by an EOL (End Of Line) request by a serial communication tool.

Step 1: based on the activated charcoal filter (ACF) load degree

Step 2: based on ...

1. the engine speed change at idle speed
2. the deviation of lambda-controller
3. manifold air pressure (MAP) change at idle speed

Step 3: based on the difference between the measured air mass flow before and during a CPS opening

The first check of the CPS is based on the ACF- load degree. The "Canister Load diagnosis" is calculated permanently until the complete check CPS is finished.

During the next check, the CPS is evaluated based on the engine speed change at idle speed. To this effect, the CPS is opened for a short time and the engine speed monitored for a certain period.

After this check has been enabled for the first time, it is requested during each idle speed phase. This is repeated as long as a result has been reached. This check is not bound to one IS phase, but can be distributed to several IS phases.

During this check the lambda deviation will also be checked.

In step 3 the CPS is considered on the basis of the measured mass air flow before and during a CPS opening phase.

If the CPS is detected to be not OK after all three checks have been passed (end of step 3), then the error is set.

Fuel Level Sensor

P0461, P0462, P0463, P2067, P2068

The diagnosis of the fuel level sensor signal consists of a circuit continuity check and a rationality check.

Fuel level sensor circuit continuity check

The signal of the fuel level sensor is monitored concerning the valid range. This range depends on the used fuel level sensor.

If the left or right fuel level sensor signal is above the upper threshold, a short circuit plus is detected. If the left or right fuel level sensor signal is below the lower threshold, an appropriate fault code for the left or right sensor is set.

Fuel level sensor signal rationality check (plausibility error)

The engine management system of every BMW has the capability to calculate fuel consumption. For the fuel level sensor plausibility check, this calculated consumption is compared with the difference of the fuel level signal. When the calculated fuel consumption reaches an appropriate and predetermined amount (for example five gallons), the calculated fuel consumption is compared to the change in fuel level as indicated by the fuel level sensors. If the difference is greater than the applicable threshold value, a stuck fuel level sensor fault is detected and an appropriate fault code is set.

If a fault is present, the OBD II EVAP leak monitor will run using a substitute value of 85% total fuel tank volume.

The 85% substitute value will assure that in every case the required 0.020 inch leak is detected by the OBD II system.

Scheme 252

Scheme 253

Scheme 254

Ambient Temperature Signal Plausibility Check

P0071

Input parameters for monitoring

1. ECT
2. engine state
3. engine stop time
4. ambient temperature after engine stop (last driving cycle)
5. ambient temperature at start
6. actual ambient temperature
7. vehicle speed
8. engine run time after start

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 met 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 decremented.

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.

Trim Control Plausibility Monitoring

P2096/2098, P2097/2099

The trim control plausibility monitoring detects a high deviation of the l-share of lambda trim control. If it exceeds given thresholds the following malfunction is detected

Fuel trim above limit

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

FAULT CODE CHART

Scheme 255

Upstream Oxygen Sensor - Short Circuit Monitoring

P0131/0151, P0132/0152

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.

FAULT CODE CHART

Upstream Oxygen Sensor - Open Circuit Monitoring

P112C/112D, P2243/2247, P2626/2629

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

FAULT CODE CHART

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

Upstream Oxygen Sensor - Signal Controller Monitoring

P3022/3023, P3024/3025

Sec (e) (7.2.1)

After an ECU reset, the WRAF sensor controller is started and the diagnosis determines the time until the initialization, has been performed in the allowed time. If not successful, then a DTC will be stored. If this is successful, then the difference is checked between the present error counter and the stored value of this error counter at ECU reset, (switching from Key "OFF" to Key "ON") or at clearing error memory and after each function call, in case a difference between both counters was found. If there is a difference, another counter is incremented.

If this counter is higher than a threshold, a SPI communication error is stored.

FAULT CODE CHART

All of the above checks are performed internal to the ECU. (See )

Upstream Oxygen Sensor - Signal Activity Check

P2414/2415

The oxygen sensor signal activity check monitors if the sensor is attached to the exhaust pipe and whether the exhaust is sampled correctly (no leakage). A malfunction is detected if the oxygen sensor voltage is above a threshold (shows too lean mixture in part load or full load)

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

B1S1 P2414

B2S1 P2415

Upstream Oxygen Sensor - Swapped Sensors Check

P0040

Upstream Oxygen Sensor - Active Signal Check (Shift to lean / rich)

P2195, 2196, 2197, 2198

This monitor is an enhancement of the Downstream Oxygen Sensor - Active Signal Check (Stuck lean / rich) and the Trim Control Plausibility Monitoring. Its purpose is to help determine the root cause of a stocking downstream sensor signal or a implausible high i- share of the fuel trim controller.

The monitor will only be enabled if a fuel correction fault has been detected and a malfunction code has been stored (P2096 - P2097 - P2098 - P2099)

OR

if the rear sensor signal check has detected, that the rear sensor signal is very rich or very lean and the corresponding malfunction fault code has stored (P114A - PI 14B - PP114C-P114C)

If one of the listed fault codes exists, this diagnosis will be enabled to determine if the root cause of the malfunction is due to a stuck signal or characteristic line shift of the upstream O2 sensor or due to a stuck signal of the downstream O2 sensor or a system malfunction, i.e. vacuum leak, injector, etc...

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

Upstream Oxygen Sensor - Signal Dynamic Monitoring (Slow Response)

P0133/0153

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. the relation between the amplification of the oxygen sensor and the model is monitored and detects the following malfunction

Sensor signal too slow

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

B1S1 P0133

B2S1 P0153

Upstream Oxygen Sensor - Signal Monitoring During Fuel Cut-off

P2297/2298

The oxygen sensor signal monitoring during fuel cut-off detects if the oxygen sensor signal is not plausible during fuel cut-off. A malfunction is detected if the oxygen sensor voltage is outside the normal operating voltage range (3.1 V ... 5.68 V). )*

If the oxygen sensor signal voltage is between 2.1 ... 3.1 V during fuel cut-off, then the signal is not plausible.

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

B1S1 P2297

B2S1 P2298

If the oxygen sensor signal voltage is above a threshold during fuel cut-off (e.g. 5.6 V)* ) or below a threshold (e.g. 2.1 V )* ) then the open circuit diagnostic function is triggered (see chapter ' OXYGEN SENSOR MONITORING - OPEN CIRCUIT '). The fault processing continues in this function.

)* For exact values please have a look at the summary table!

Upstream Oxygen Sensor - Heater Monitoring

P3026/3027

The diagnosis strategy is based on a statistical evaluation of the oxygen sensor ceramic temperature over a pre-defined number of monitoring cycles.

The oxygen sensor ceramic temperature shall be obtained indirectly via the measured internal resistance of the sensor.

If the sensor is not ready after a defined time (e.g. 30s after start) )* the sensor is set to forced readiness mode and the Upstream Oxygen Sensor Heater Monitoring is started.

Two cases can appear

1. sensor temperature is invalid (no measurement of sensor temperature possible because of an ECU internal (electrical) failure) =>P165F/P166F is stored
2. sensor temperature is below a threshold => normal failure detection

A low sensor temperature can be caused by a weak heater or a open circuit in the temperature measurement line (line UN). After a low sensor temperature has been detected, the open circuit diagnosis is triggered to check, if an open circuit in line UN is present. If there is an open circuit, then open circuit fault code (P2243/P2247) is stored (see chapter ' OXYGEN SENSOR MONITORING - OPEN CIRCUIT ' and picture below).

If there is no open circuit present, then the heater fault code is stored (P0135/P0155).

)* For exact values please have a look at the summary table!

SUMMARY

Scheme 256

Upstream Oxygen Sensor - Heater Circuit Monitoring

P0030,0031,0032,0050,0051,0052

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.

FAULT CODE CHART

Downstream Oxygen Sensor - Circuit Monitoring

P0137,0138,0140,0157,0158,0160

The oxygen sensor electrical monitor detects the following malfunctions

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

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

FAULT CODE CHART

Downstream Oxygen Sensor - Signal Dynamic / Plausibility Check During Fuel Cutoff

P0139/0159

The following plausibility and activity monitoring is carried out: (e) (7.3.2)

Sensor signal plausibility and signal activity monitoring is performed during coasting conditions during fuel cut-off (slow response / sensor signal range too small).

A malfunction is detected, if the sensor signal is not below a threshold after a short time after entering fuel cut-off. This short time is needed to purge the exhaust pipe. Usually the signal falls from fuel trim correction setpoint (e.g. 680 mV) to a voltage near 0mV.

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

FAULT CODE CHART

Downstream Oxygen Sensor - Dynamic / Transition Time in Sensor Midpoint Range Monitoring

P1130/1131

This function monitors the transition Time in sensor midpoint range of the downstream sensor voltage. When a fuel cut-off phase starts, the following steps will be executed

1. sensor voltage must be above a threshold (signal must be rich enough, to measure the switchtime) Remark: Usually the signal starts at fuel trim control setpoint (e.g. 650 mV)
2. sensor voltage value is stored (= "start-value")
3. switchtime measurement is started, when the signal is e.g. at 75 % of start value Remark: The measurement start and stop- value are relative to the start value, to measure always the switchtime around the fuel trim control setpoint.
4. switchtime measurement is finished, when the signal is e.g. at 40 % of start value
5. measured switchtime is corrected over mass air flow

The transition time ("switchtime") is represented by a cycle counter. This switchtime is measured over x )* fuel cut-off phases. The mean value after x fuel cut- off phases is compared with a failure threshold.

If this value is above a threshold, a malfunction is detected and the corresponding fault code is stored.

FAULT CODE CHART

)* For exact values of thresholds etc. please have a look at the summary table!

Scheme 257

Downstream Oxygen Sensor - Active Signal Check (Stuck lean / rich)

P114A, 114B, 114C, 114D, P2279,2271,2271,2273

This monitor consists of two parts.

1. Part one monitors the downstream sensor voltage during active fuel trim controller p- share. If the fuel trim control is active, the downstream sensor voltage must be in a band around the trim control setpoint. If the voltage is outside this band )*, a mass air flow integral is incremented. If this integral is over a threshold, a malfunction is detected (see also picture below!). When the downstream sensor voltage will not switch to rich before the integral is over a threshold after a fuel cut-off phase, then this fault will be stored, too. If the above mentioned malfunctions are detected, the corresponding fault code is stored. FAULT CODE CHART B1S2 B2S2 Downstream sensor voltage too low P114B P114D Downstream sensor voltage too high P114A P114C )* For exact values of thresholds etc. please have a look at the summary table!
2. Part two - Downstream Active Test: This monitor is an enhancement of the Downstream Oxygen Sensor - Active Signal Check (Stuck lean / rich) and the Trim Control Plausibility Monitoring. Its purpose is to help determine the root cause of a stocking downstream sensor signal or a implausible high i- share of the fuel trim controller. The monitor will only be enabled if a fuel correction fault has been detected and a malfunction code has been stored (P2096 - P2097 - P2098 - P2099) OR if the rear sensor signal check has detected, that the rear sensor signal is very rich or very lean and the corresponding malfunction fault code has stored (P114A - PI 14B - PP114C-P114C) If one of the listed fault codes exists, this diagnosis will be enabled to determine if the root cause of the malfunction is due to a stuck signal or characteristic line shift of the upstream O2 sensor or due to a stuck signal of the downstream O2 sensor or a system malfunction, i.e. vacuum leak, injector, etc... If it has been determined that the upstream O2 signal was the root cause of the fuel correction fault, the appropriate DTC will be stored along with the fuel correction or with the downstream sensor stuck DTC (see chapter ' «UPSTREAM OXYGEN SENSOR - ACTIVE SIGNAL CHECK (SHIFT TO LEAN / RICH)»(ref-288022-S20411520812008061700000) '). If it has been determined that the downstream sensor signal was the root cause of the fuel correction fault, the appropriate DTC (see table below) will be stored along with the fuel correction or with the downstream sensor stuck DTC. This function will also detect, if the oxygen sensor wire harness has been cross connected, i.e., Bank 1 with Bank 2. When this failure is present, the downstream sensor voltages of bank 1 and 2 are on opposite limits. If one of the above mentioned malfunctions is detected, the corresponding fault code is stored. FAULT CODE CHART B1S2 B2S2 Downstream sensor stuck rich P2271 P2273 Downstream sensor stuck lean P2270 P2272 Downstream sensors interchanged P0041

Downstream Oxygen Sensor - Heater Circuit Monitoring

P0141,0161,P0036,0037,0038,0056,0057,0058

Monitoring Function: Circuit

For proper function of the oxygen sensor, the sensor element must be heated.

A non functioning heater delays the sensor readiness for closed loop control and thus influences emissions.

The monitoring strategy is based on the comparison of the O2 sensor heater resistance to an absolute threshold during coasting conditions where the exhaust temperature is sufficiently low as to cause the sensor ceramic temperature to fall outside normal operating levels, in cases where the heating power is insufficient.

The cooling energy of the exhaust gas is calculated and compared to a calibrated threshold.

The heater monitor is active if the calculated energy is equal or exceeds the threshold. Then the O2 sensor heater is compared to a calibrated threshold. If the heater resistance is equal or exceeds the threshold, an O2 sensor heater malfunction is detected and the corresponding fault code is stored.

Corresponding fault code

B1S2 P0141

B2S2 P0161

Monitoring Function: Power stage

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 power stage is monitored internally by the driver. 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.

FAULT CODE CHART

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 temporary or permanently deactivated during the driving cycle. The turn-on delay at the 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. a calibrated delay time, after end of engine start, has elapsed
3. the engine coolant temperature must have exceeded a calibrated threshold or the modeled engine coolant temperature (substitute for a faulty temperature sensor minimum) must have exceeded a calibrated threshold after a calibrated period of time
4. no secondary air activity Closed loop lambda operation is disabled during the driving cycle, if the following operating condition, which permits only mixture enrichment by the lambda controller, is fulfilled
5. when Catalyst overheating prevention is active.

Only for linear Lambda Sensor

1. the A/F ratio set-point value lies below oxygen sensor's measurable limit - in this case only A/F mixture enrichment can be executed by the lambda control (no closed loop operation) the moment the set-point value exceeds the measurable threshold. Closed loop lambda operation is further deactivated during a driving cycle when any of the following conditions are fulfilled
2. during fuel cut-off or cylinder shut-off and immediately afterwards till the oxygen sensor again starts indicating correct values (the waiting time depends on integrated mass airflow or on a calibrated delay time).
3. the mass air flow is below a calibrated threshold that leads to the minimum possible injection time.
4. Secondary air system active

1. measured ECT

1. Measured ECT
2. Calculated (modeled) ECT

1. ECT (at start)
2. IAT (at start)
3. ambient temperature (at start)
4. engine off timer

Engine off timer Monitoring

P1515,1551

1. ECT at engine stop
2. ECT
3. relative time counter via CAN

Thermostat

P0128,0597,0598,0599

The input parameters used for monitoring are

1. Engine coolant temperature
2. Intake air temperature
3. Ambient air
4. Engine load

Scheme 258

A comparison between the measured coolant temperature and the "warmed-up temperature" is done after a specific time interval. The interval itself is based on the coolant temperature model (Function of intake air mass).

As soon as the model temperature exceeds the thermostat opening temperature and all other monitoring conditions are fulfilled at the same time, a valid diagnosis occurs.

At that time, if the measured coolant temperature is higher than warmed-up temperature, the thermostat is concluded as normal thermostat.

On the contrary, if the measured coolant temperature is lower than warmed-up temperature, the thermostat is concluded as opened stuck thermostat.

Intake Air Plausibility Check

P0111, 111E, 111F

1. ECT
2. Ambient temperature at start and continuously
3. IAT
4. Vehicle speed
5. Engine speed

Variable Camshaft Timing (Vanos) (detection of mechanical IVVT error)

P0012/0015

The BMW-Vanos is a combined hydraulic and mechanical camshaft control unit, managed by the ECU. The double Vanos allows the engine to control valve-timing continuously for both intake and exhaust camshafts. The electronically control of the Vanos positions is dependant on engine speed, load and temperature.

The diagnosis is monitoring the correct mechanical function of the variable camshaft timing. The diagnosis carries out a continuous rationality check of the Vanos function. If a malfunction is detected, an error bit will be set and sent to the Error management module. This module produces the final information for setting the corresponding DTC.

The diagnostic strategy for inlet and exhaust camshaft is identical.

Camshaft position sensor (CMP)

P0340/0365/1300/130A/0344/0369/1554/1553/0016/0017

The detection of each camshaft position is done by an active hall sensor and a cam wheel, "3 asymmetric teeth". The camshaft sensor delivers 3 high and 3 low phases of different length per 720°CRK. The high or low pegel of the signal at the reference gap of the crankshaft signal determines the position of the engine within the combustion cycle. With that information, a engine position is calculated from the crankshaft position sensor within a range from [0 to 720[ °CRK

The following malfunctions are detected

MALFUNCTIONS REFERENCE CHART

Camshaft Crankshaft synchronization

P0341

The diagnosis is performed at every edge of the selected camshaft signal and at the reference gap of the CKP sensor signal. With the period between current event and the last event, the function eliminates the edges of the camshaft which are not inside the designed window. The window is calculated from the designed position plus / minus a tolerance. The tolerance is expanded by the range of the variable valve timing, when the camshaft is not in lock position.

The following malfunctions are detected

MALFUNCTIONS REFERENCE CHART

Crankshaft position sensor (CRK)

P0335/0370/0373

The detection of crankshaft position is done by an active hall sensor and a crank wheel, "e.g. 60 minus 2 teeth". A reference gap, "e.g. of two teeth" allows the detection of the top dead center of cylinder 0. The crankshaft sensor delivers a certain number of high and low phases per 360°CRK. The transition from high to low is a falling edge; from low to high is a rising edge. Only the falling edges are counted. The difference between two falling edges is 6° CRK.

The following malfunctions are detected

MALFUNCTIONS REFERENCE CHART

A teeth counter is incremented at every falling edge of the CRK sensor signal. If plus or minus one tooth is detected during the last 360° CRK at the reference gap, the tooth number debounce counter will be incremented. If the counter exceeds a limit, a CRK tooth error is delivered to the error management.

If more then one tooth plus or minus is detected the CRK looses synchronization and a CRK sync debounce counter will be incremented. If the counter exceeds a limit, a CRK sync error is delivered to the error management.

The detection of a tooth period error is done by an acceptance window. The expected tooth period is multiplied and divided with an engine speed dependency factor. The result is a bottom and a top limit of tooth period, in which the transition from high to low of the electrical signal has to occur. If a tooth period is not valid, the tooth period error debounce counter will be incremented. If the counter exceeds a limit, a CRK tooth per error is delivered to the error management.

Detection of implausible crankshaft signal is based on the detection of CAM signals without receiving correct CRK signal. If 12 or more CAM edges are detected (eg. 2 working cycles), without valid synchronization of the crankshaft, then CRK plaus error is detected and delivered to the error management. If no CRK signal at all is received, the symptom is "missing signal", else the symptom is "implausible signal".

ETC spring check (start routine)

(P169A, P1694)

This Diagnosis checks if the throttle spring is working correctly and if the throttle limp home position can be reached.

The diagnosis is performed at the beginning of every driving cycle at ignition "Key ON" position.

Electronic Throttle Control (ETC) Motor Control Performance

(P1637, P1639)

This diagnosis is able to detect a too slow or jammed actuator. The given pulse width modulation signal (MTCPWM) exceeds the position controller permissible maximum value for longer than designated (Max short or Max Long) time.

If either of the times is exceeded, the appropriate DTC will be stored.

Also if a maximum allowed difference between throttle actual value and setpoint value is exceeded, a DTC is stored.

ISC (Idle Speed Control) Actuator

90506,0507

Air Mass Flow Meter - Rationality check

P1415, 1424

Manifold Differential Pressure Sensor - Rationality check

P1124,P1104,1105

Strategy

Principle

1. Sensors that can affect emissions or are used to monitor other component / system are monitored for circuit continuity and short to battery voltage and / or to ground using high and low voltage signal limit.
2. Actuators that can affect emissions or are used to monitor other component / system are monitored by power stage voltage check for valid signals.
3. For some of sensors or actuators, plausibility checks are included to ensure proper operation of the components.

Monitoring Strategy for sensors

1. Sensor signals out of a defined range are regarded as circuit malfunctions shorted to BATT, GND or Open circuit.

Monitoring Strategy for actuators

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

Rationality Check

1. Components are checked for the integrity of their values. This is accomplished by the use of a model or other sensor inputs. If a component does not function as expected or the integrity is in question (values are not within a threshold) it is considered out of range / plausible.

Comprehensive Monitoring for following sensors and actuators

1. Throttle Position Sensor - Electrical Check
2. Mass Air Flow Sensor - Electrical Check
3. Coolant Temperature Sensor (ECT) - Electrical Check
4. Camshaft Position Sensor
5. Vehicle Speed Signal
6. Injector Valve Diagnosis
7. Idle Speed Plausibility
8. Differential Pressure Sensor - Electrical check
9. Knock Sensor diagnosis
10. TCU error diagnosis
11. CAN Communication
12. Pedal Position Sensor
13. Ambient Pressure Sensor - Electrical check
14. Ambient Pressure Sensor - Rationality Check
15. EVAP - DMTL Valve, Electrical check
16. EVAP - DMTL Heater, Electrical check
17. EVAP - DMTL Pump, Electrical check
18. EVAP - Purge Control Valve, Electrical check

Listing of all ECM Input and Output Signals

ECM INPUT AND OUTPUT SIGNAL LIST

Calculated load and fuel trim determination

The calculated engine load "LOAD_CLC [%]" is based on the measured mass air flow (metered by the hot-film air-mass 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

REFERENCE CHART

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

Start Emission Reduction Strategy Monitoring

P1561,1562

All parameters, that are relevant during the cat heating phase, are monitored by standard monitoring functions

MONITORING FUNCTION REFERENCE CHART

Illustration 1 (Standard monitoring functions during Cat Heating - Overview)

To fulfill the legal requirements, the monitoring of the idle speed is now extended to the cold start phase. In case of an error, the specific P-Codes

1. P1561 Cold Start Idle Air Control System RPM lower than expected
2. P1562 Cold Start Idle Air Control System RPM higher than expected

are set.

Scheme 259

Illustration 2 (Idle speed control)

During cat heating, it is essential to make sure, that enough thermal energy is applied to the catalyst to heat it up as quick as possible.

Therefore it is target to limit the ignition timing to the earliest possible value during the cat heating phase.

If there would be a demand for more torque and therefore for an advanced ignition timing beyond the limits, the engine would be allowed to stall instead of fulfilling the demand.

The torque limits are calibrated the way that the emissions stay below 1.5 times of the limits.

Scheme 260

Illustration 3 (Flowchart)

Known System

During normal driving, the ignition timing desired torque corresponds to the air mass desired torque, which determines the ignition timing. During the cat heating phase, the cat heating torque is added to the air mass desired torque, resulting in a higher reference air mass torque.

The efficiency, desired torque divided by the reference torque, determines the ignition timing.

New System (BMW-development)

The earliest possible ignition timing is determined by the limitation of the torque reserve to a minimum value during the cat heating phase. For this, the required minimum cat heating torque is subtracted from the reference air mass torque. The thus reduced efficiency leads to a safe ignition retard and limits the ignition timing during the cat heating measures.

Limitation of ignition timing to the earliest possible ignition timing during the cat heating phase by limitation of torque reserve to the minimum required torque reserve.

Scheme 261

Illustration 4 (Diagram torque characteristic line and ignition timing)

The maximum ignition timing after cold start with new BMW method

Scheme 262

Illustration 5 (Measuring Data)