Diagnostic Trouble Codes with Test Charts (v8 & v12) BMW X5 E53

INTRODUCTION

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. BMW vehicles are equipped with an OBD-II self-diagnostic system for accessing Diagnostic Trouble Codes (DTC) using a generic scan tool connected to vehicle Data Link Connector (DLC). (Scheme 190)- (Scheme 192). BMW trouble codes can be accessed using BMW's Diagnostic Information System (DIS) or Mobile Diagnostic Computer (MoDiC).

DME/Motronic/Siemens control unit provides a substitute value if a failure occurs in an engine performance related component, such as engine (coolant) temperature sensor, intake air temperature sensor, airflow meter or exhaust gas oxygen sensor. See ENGINE MANAGEMENT SYSTEM IDENTIFICATION table. These substitute values are canceled when normal engine operation is resumed.

If no DTCs are present after entering self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).

Note. All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated otherwise in testing procedures.

Scheme 190

Scheme 191

Scheme 192

Scheme 193

Beginning with model year 2001, the E39 and E53 eliminated the 20-pin BMW diagnostic connector from the engine compartment. (Scheme 193) The 16-pin OBD-II connector located inside vehicle is the only diagnosis port. The 7-series (E38) will continue to use the 20-pin connector until the end of production. The 16-pin OBD-II connector has been in all BMWs since 1996 to comply with OBD-II regulations requiring a standardized diagnostic port. Before 2001, only emissions relevant data could be extracted from OBD-II connector because it did not provide access to the TXD (D-bus). The TXD line is connected to pin No. 8 of the OBD-II connector on vehicles without the 20-pin diagnostic connector. The OBD-II connector is located in driver's footwell to left of steering column for E39 and E53 vehicles.

The Motronic/Siemens control unit provides a substitute value if a failure occurs in an engine performance related component, such as engine (coolant) temperature sensor, intake air temperature sensor, airflow meter or exhaust gas oxygen sensor. These substitute values are canceled when normal engine operation is resumed.

If no DTCs are present after entering self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). For engine management system identification, see ENGINE MANAGEMENT SYSTEM IDENTIFICATION table.

Note. All voltage tests should be performed with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated otherwise in testing procedures.

ENGINE MANAGEMENT SYSTEM IDENTIFICATION

CHECK ENGINE LIGHT

CHECK ENGINE or Malfunction Indicator Light (MIL) is illuminated when any of the following occur

Scheme 194

1. Completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present. (Scheme 194)
2. Immediately if a catalyst damaging fault occurs.
3. A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed 1.5 times the standard.
4. Manufacturer-defined specifications are exceeded.
5. An implausible input signal is generated.
6. Catalyst deterioration causes HC-emissions to exceed a limit equivalent to 1.5 times the standard.
7. Misfire faults occur.
8. A leak is detected in the evaporative system.
9. The oxygen sensors observe no purge flow from the purge valve/evaporative system.
10. Engine control module fails to enter closed-loop operation within a specified time interval.
11. Engine control or automatic transmission control enters a limp home operating mode.
12. Key is in the ignition on position before cranking (Bulb Check Function).

BMW DIAGNOSTIC HARDWARE

Note. BMW utilizes 2 main types of diagnostic hardware: the Diagnostic Information System Plus (DISplus) and the Group Tester One (GT-1). See ON-BOARD DIAGNOSTICS .

DIS Plus

BMW DIS Plus diagnostic system features a comprehensive multimeter system (including an oscilloscope) that is used to perform various tests and measurement during the diagnosis and troubleshooting procedures. DIS also includes the Technical Information System (TIS). TIS is the same system that operates through dealer main computer system.

Group Tester One (GT-1)

GT-1 replaces the MoDiC series of portable diagnostic tools. It has the same processor as the DISplus. Other features include a DVD ROM drive, TFT color display, integrated PCMCIA card reader, integrated chip card reader, touch screen (same as DISplus), workshop grade case, ASM-technology motherboard, temperature operating range from 35°F to 105°F, 2.5 hours of operation with a fully charged battery, and can be powered by vehicle battery.

A diagnostic cable is used to connect diagnostic head to a vehicle with the 20 pin underhood connector. Cable consists of 20 pin connector, cable and 21-pin plug for connection to the head. An OBD-II diagnostic cable is used to connect diagnostic head to OBD-II diagnostic connector.

Hard & Intermittent Failures

A fault code is stored within the respective control module upon first occurrence of a fault in system being checked. CHECK ENGINE light will not be illuminated until completion of second consecutive driving cycle where previously faulted system is again monitored and a fault is still present or a catalyst damaging fault has occurred. If second drive cycle was not complete and specific function was not checked, PCM counts third drive cycle as next consecutive drive cycle. CHECK ENGINE light is illuminated if function is checked and fault is still present.

If an intermittent fault is present, and it does not cause a fault to be set through multiple drive cycles, 2 complete consecutive drive cycles with fault present are required for CHECK ENGINE light to be illuminated. Once CHECK ENGINE light is illuminated it will remain on unless specific function has been checked without fault through 3 complete consecutive drive cycles.

Fault code will also be cleared from memory automatically if specific function is checked through 40 consecutive drive cycles without fault being detected or with use of DIS Plus or GT-1 scan tool. To clear a catalyst damaging fault from memory, condition under which fault occurred must be evaluated for 80 consecutive cycles without fault reoccurring.

OBD-II Diagnostics

Malfunction Indicator Light (MIL) can be diagnosed with an aftermarket scan tool that allows technicians without BMW special tools or equipment to diagnose an emission system failure. With the use of a universal scan tool connected to Data Link Connector (DLC), an SAE standardized DTC can be obtained, along with condition associated with the illumination of MIL. Using DISplus or GT-1, a fault code and the conditions associated with its setting can be obtained prior to the illumination of the MIL.

OBD-II Diagnostic Trouble Codes (DTC) are designed to be identified by their alpha/numeric structure. DTCs start with letter "P" for powertrain related systems. (Scheme 195) DTCs are stored whenever the Check Engine Light (MIL) is illuminated. Universal diagnostic access to DTCs is via a standardized Diagnostic Link Connector (DLC) using a standardized tester (scan tool). DTCs only provide one set of environmental operating conditions when a fault is stored. This single freeze frame refers to vehicles environmental conditions for a specific time when fault first occurred. Information which is stored is limited in scope. This information may not even be specific to type of fault. On BMW, OBD-II monitors following systems

1. Catalyst Monitoring.
2. Misfire Monitoring.
3. Evaporative (EVAP) System Monitoring.
4. Secondary Air System Monitoring.
5. Fuel System Monitoring.
6. Oxygen Sensor Monitoring.

Scheme 195

BMW Diagnostics

BMW diagnostic trouble codes are stored as soon they occur even before the Check Engine Light (MIL) comes on. BMW codes are defined by BMW, Bosch and Siemens to provide greater detail to fault specific information.

On Siemens systems, one set of 4 fault-specific environmental conditions are stored with the first fault occurrence. This information can change and is specific to each fault code to aid in diagnosing. A maximum of 10 different faults containing 4 environmental conditions can be stored.

On Bosch systems, a maximum of 4 sets of 3 fault-specific environmental conditions are stored within each fault code. This information can change and is specific to each fault code to aid in diagnosis. A maximum of 10 different faults containing 3 environmental conditions can be stored. BMW codes also store and display a time stamp when the fault last occurred. A fault qualifier gives more specific detailed information about the type of fault (upper limit, lower limit, disconnection, plausibility, etc.).

BMW codes are capable of recording current fault status. Code will advise whether fault is actually still present, not currently present or intermittent. Fault specific information is stored and accessible through DIS Plus or GT-1. BMW codes determine diagnostic output for BMW DIS Plus or GT-1.

Readiness Code

Readiness code provides status (yes/no) of the system having completed all required monitoring functions or not. The readiness code is displayed with an aftermarket Scan Tool or the DISplus/GT-1. The code is a binary (1/0) indicating the following

1. 0 = Test not completed or not applicable - 6 cylinder vehicles (not ready - V8 and V12)
2. 1 = Test completed - 6 cylinder vehicles (ready - V8 and V12)

A readiness code must be stored after any clearing of fault memory or disconnection of PCM. A readiness code of "0" will be stored after a complete diagnostic check of all components/systems (that can turn on Malfunction Indicator Light) is performed. Readiness code was established to prevent anyone with an emissions related fault and a Malfunction Indicator Light on from disconnecting battery or clearing fault memory to manipulate results of emissions test procedure. Complete readiness code is equal to one byte (8 bits). Every bit represents one complete test and is displayed by scan tool

1. 0 = EGR monitoring (= 0, N/A with BMW)
2. 1 = Oxygen sensor heater monitoring
3. 1 = Oxygen sensor monitoring
4. 0 = Air condition (= 0, N/A with BMW)
5. 1 = Secondary air delivery monitoring
6. 1 = Evaporative system monitoring
7. 0 = Catalyst heating
8. 1 = Catalyst efficiency monitoring

Drive vehicle in such a manner that all tests listed above can be completed. When complete readiness code equals "1" (ready) then all tests have been completed and system has established its readiness.

Readiness code can be checked with DISplus/GT-1. This is helpful in verifying that drive cycle criteria was achieved. A repair can be confirmed before returning vehicle to customer by a successfully completed drive cycle. (Scheme 194)

RETRIEVING & ERASING DIAGNOSTIC TROUBLE CODES

OBD-II and BMW Diagnostic Trouble Codes (DTC) can be retrieved or erased using BMW or a generic scan tool connected to Data Link Connector (DLC). (Scheme 190)- (Scheme 192). Follow scan tool manufacturer's instructions. BMW diagnostic hardware directs user to a specific test routine which provides diagnostic information.

DRIVE CYCLES

For drive cycle information (Scheme 194)

SUMMARY

If no hard DTCs are present, driveability symptoms exist or intermittent DTCs exist, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnosis procedures.

DIAGNOSTIC TROUBLE CODE CROSS-REFERENCE & TABLES

BMW Diagnostic Trouble Codes (DTCs) are separated by model, test group reference, engine type and date of manufacture. See DIAGNOSTIC TROUBLE CODE TABLE CROSS-REFERENCE table to determine which specific table applies to a particular fuel system type, engine, and model year. Model specific tables contain OBD-II (PCode) and BMW-specific (BMW-FC) DTCs. DTCs in model-specific tables link to appropriate diagnosis, if available. After performing diagnosis, go to TEST GROUP IDENTIFICATION for additional testing.

Note. Diagnosis is not available for all DTCs.

DIAGNOSTIC TROUBLE CODE

TABLE A: TEST GROUP 1BMXV04.9S62, ENGINE S62 (M5 & Z8, 9-00 TO 8-01)

TABLE B: TEST GROUP 1BMXT04.4E53, ENGINE M62/E53 (4-00 TO 9-01)

TABLE C: TEST GROUP 1BMXV04.4LEV, ENGINE M62/E39 (9-00 TO 8-01) & M62/E38 (3-00 TO 8-01)

TABLE D: TEST GROUP 1BMXV05.4LEV, ENGINE M73/E38 (9-1-00 TO 8-31-01)

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Scheme 199

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Scheme 210

Scheme 211

Scheme 212

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Scheme 215

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Scheme 219

Scheme 220

Scheme 221

Scheme 222

Scheme 223

Scheme 224

Scheme 225

CONNECTOR IDENTIFICATION

Control module uses a combination of a 9-pin, 24-pin, 40-pin and 52-pin connector. For control module connector identification (Scheme 226)- (Scheme 229).

Control Module Connector Terminal Identification (9-Pin Connector). Scheme 226

Control Module Connector Terminal Identification (24-Pin Connector). Scheme 227

Control Module Connector Terminal Identification (40-Pin Connector). Scheme 228

Control Module Connector Terminal Identification (52-Pin Connector). Scheme 229

TEST GROUP IDENTIFICATION

BMW supplies test group information in the following 6 categories

1. «CATALYST MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12__catalyst-monitoring)
2. «MISFIRE MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12__misfire-monitoring)
3. «EVAPORATIVE SYSTEM MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12)
4. «SECONDARY AIR SYSTEM MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12__secondary-air-system-monitoring)
5. «FUEL SYSTEM MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12__fuel-system-monitoring)
6. «OXYGEN SENSOR MONITORING»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts-v8-v12__oxygen-sensor-monitoring)

Specific engine family test group identification number (

for example: 2BMXV03.0LER

) can be found on emission label in engine compartment. To cross reference test group category (catalyst monitoring, misfire monitoring, etc.) see

BMW TEST GROUP IDENTIFICATION

table.

BMW TEST GROUP IDENTIFICATION

CATALYST MONITORING

Efficiency of catalyst operation is determined by evaluating oxygen storage capability of catalytic converter using pre and post oxygen sensor signals. A correctly operating catalyst consumes or stores most of oxygen present in exhaust gas. To determine if catalyst is working correctly, signal of post cat oxygen sensor is evaluated over course of several pre-catalytic oxygen sensor oscillations. During evaluation period, signal of post-catalytic sensor must remain within a relatively constant voltage range.

Under normal closed loop operation, changing air/fuel ratio in exhaust gas results in lambda oscillations at pre-catalyst sensor. These oscillations are dampened by oxygen storage activity of catalyst and are reflected at post-catalyst sensor as a fairly stable signal. Depending on how vehicle is being operated at time of evaluation and type of catalyst or coating being used, signal may be in lean or rich voltage range.

CATALYST SENSOR MONITORING CONDITIONS

Scheme 230

Scheme 231

1. Catalyst Monitoring General Description - Catalyst monitoring is based on monitoring its oxygen storage capability. Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability. To determine catalyst efficiency, oscillation of upstream sensor is needed to calculate oxygen-in and-output (catalyst) by engine air mass and lambda-deviation. Downstream sensor signal for a threshold catalyst then is derived from this basic value. Any time real sensor signal oscillation (downstream) corresponds to model, a defective catalyst is recognized. (Scheme 230)
2. Computation Of Amplitude Ratio - First step is the computation of amplitude of signal oscillations of lambda sensor upstream versus downstream of catalyst. This is accomplished by extracting oscillating signal component, computing absolute value and averaging over time. Quotient of downstream amplitude value divided by upstream amplitude value is called amplitude ratio (AR). This AR is basic information necessary for catalyst monitoring. It is computed continuously over a certain engine and speed range. Signal paths for both sensor signals are identical. Thus, variations like an increase of control frequency affect both signal paths in the same way and are compensated by the division.
3. Postprocessing - Actual amplitude ratio is compared with a limit value according to load and speed range engine is operating in. The result of this comparison, difference of both values, is accumulated separately for each range. Even short time periods of driving in a certain range yield additional information. By using separate load and speed ranges in combination with the accumulation of information, a monitoring result can be obtained during an FTP cycle.
4. Fault Evaluation - Accumulated information about the amplitude ratio becomes more and more reliable as different load and speed ranges are used during a driving cycle. If amplitude ratio is greater than fixed map values, a fault is detected and an internal fault flag will be set. If fault is detected again, in next trip the MIL will be illuminated. (Scheme 231)
5. Check Of Monitoring Conditions - Monitoring principle is based on detection of relevant oscillations of downstream sensor signal during regular lambda control. It is necessary to check driving conditions for exceptions where no regular lambda control is possible (e.g. fuel cutoff). During such periods, and for a certain time afterward, the computations of amplitude values and post-processing is halted. Thus, a distortion of monitoring information is avoided.
6. Electrically Heated Catalyst Monitoring - Heating of electrically heated catalyst is only conducted at every engine start when numerous switch-on conditions are met and no faults are stored for following ranges: CAN ECM. CAN instrument cluster. Output stage injection valve. Misfire (catalyst damage). Output stage secondary air injection pump. Output stage secondary air injection valve. Coolant temperature sensor. Crankshaft sensor/reference point.

Adjustment and diagnostic for the heater of the electrically heated catalyst is conducted by a separate control unit directly communicating with ECM. If heating element is supplied by electrical current, it begins to glow. The heat generated by this process is lead to a small catalyst located directly behind heating element. Heating-time is independent from input parameters and always has the same duration.

Heating current is compared as a diagnostic criteria (1.5 x standard) to a defined current threshold. If heating current decreases defined threshold for a defined duration, a relevant fault is stored and MIL is illuminated during next driving cycle. In addition to above mentioned diagnostics, further electrical diagnostics and plausibility-checks are conducted, which cause a break-off or a lock of the heating-cycle and a relevant fault storage in case of a fault. Both exhaust systems are separately checked.

Scheme 232

1. Catalyst Monitoring General Description - Catalyst monitoring is based on monitoring its oxygen storage capability. Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability. To determine catalyst efficiency, oscillation of upstream sensor is needed to calculate oxygen-in and-output (catalyst) by engine air mass and lambda-deviation. Downstream sensor signal for a threshold catalyst then is derived from this basic value. Any time real sensor signal oscillation (downstream) corresponds to model, a defective catalyst is recognized. (Scheme 230)
2. Computation of Efficiency Factor - Signal of lambda-controller is filtered and multiplied by engine air mass. A value is now added, which considers downstream sensor layer. This result is representative of oxygen load into catalyst. Standard amplitude (NSA) of downstream sensor is computed by averaging measured signals. Difference between NSA and OKB is integrated and divided continuously by a time range during which catalyst monitoring is active. This factor (GW) is an indicator of the catalyst efficiency and it is determined continuously in a certain engine speed and engine load range within time of monitoring.
3. Fault Evaluation - After time range of monitoring has elapsed, efficiency factor (GW) is compared with threshold value. If GW is greater than threshold value, a fault is detected and the MIL is illuminated after next driving cycle. (Scheme 232)
4. Check Of Monitoring Conditions - Monitoring principle is based on the detection of relevant oscillations of downstream sensor signal during regular lambda control. It is necessary to check driving conditions for exceptions where no regular lambda control is possible (e.g. fuel cutoff). During such periods, and for a certain time afterward, computations of amplitude values and post-processing is halted, avoiding a distortion of monitoring information.

Scheme 233

1. Catalyst Monitoring Based On Monitoring Oxygen Storage Capability - Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability. To determine catalyst efficiency, oscillation of upstream sensor is needed to calculate oxygen in and output (catalyst) by engine air mass and lambda-deviation. Downstream sensor signal for a threshold catalyst then is derived from this basic value. Anytime real sensor signal oscillation (downstream) corresponds to the model, a defective catalyst is recognized. (Scheme 233)
2. Monitoring Cycle - Monitoring cycle is represented by the following: Computation Of Efficiency Of Catalyst - Alternating current component of voltage of oxygen sensors before and after catalyst is determined, rectified and averaged. Actual quotient of oxygen sensor voltage before catalyst and voltage of oxygen sensor after catalyst is determined. Simultaneously, theoretical quotient of this voltage of oxygen sensors is computed in relation to operating point of engine. Respective operating point is determined using parameters load and engine speed. Fault Evaluation - At end of diagnostic period, number of stored values in adaptation matrix exceeding a limit is determined. If this number of stored values itself exceeds a threshold, a defective catalyst is evaluated. Check Of Monitoring Conditions - Monitoring principle is based on detection of relevant oscillations of downstream sensor signal during regular lambda control. It is necessary to check driving conditions for exceptions where no regular lambda control is possible. During such periods, and for a certain time afterward, computations of amplitude values and the following processing is interrupted, avoiding a distortion of monitoring information.

MISFIRE MONITORING

Misfire detection must determine if misfire is occurring, identify specific cylinder(s) and the severity of misfire, and whether it is emissions relevant or catalyst damaging. (Scheme 234) To do this, control module monitors crankshaft for acceleration losses during firing segments of each cylinder based on firing order. Process of misfire detection continues well after diagnostic drive cycle requirements have been completed. Misfire detection is ongoing and is only discontinued under certain conditions. See MISFIRE DETECTION DISABLING CONDITIONS table. (Scheme 235)- (Scheme 236).

MISFIRE DETECTION DISABLING CONDITIONS

Scheme 234

Scheme 235

Scheme 236

Scheme 237

Scheme 238

1. General Description - Method of engine misfire detection is based on evaluating engine speed fluctuations. To detect misfiring at any cylinder, torque of each cylinder is evaluated by metering time between 2 ignition events, which is a measure for mean value of speed of this angular segment. This means that a change of engine torque results in a change of engine speed. In addition, influence of load torque will be determined, such as influences of different road surfaces. If mean engine speed is to be measured, influences caused by road surfaces have to be eliminated. (Scheme 237) This method consists of following main parts: Data acquisition, adaptation of sensor wheel is included. Calculation of engine roughness. Comparison with a threshold depending on operating points. Some extreme conditions, during which misfire detections should be disabled for a short time. Fault processing, counting procedure of single misfire events.
2. Monitoring Cycle - Monitoring cycle is represented by the following: Data Acquisition - Duration of crankshaft segments is measured continuously for every combustion cycle. Sensor Wheel Adaptation - Within a defined engine speed range and during fuel cut off, adaptation of sensor wheel tolerances is carried out. With progressing adaptation, sensitivity of misfire detection is increasing. Adaptation values are stored in a non-volatile memory and taken into consideration for calculation of engine roughness. Misfire Detection - Following operating steps are performed for each measured segment corrected by sensor wheel adaptation. Calculation Of Engine Roughness - Engine roughness is derived from differences of segment durations. Different statistical methods are used to distinguish between normal changes of segment duration and changes due to misfiring. Detecting Of Multiple Misfiring - If several cylinders are misfiring, calculated engine roughness values may be so low that threshold is not exceeded during misfiring, and therefore misfiring would not be detected. Based on this, periodicity of engine roughness value is used as additional information during multiple misfiring. Engine roughness value is filtered and a new multiple filter value is created. If this filter value increases due to multiple misfiring, roughness threshold is decreased. By applying this strategy, multiple misfiring is detected reliably. Calculation Of Engine Roughness Threshold Value - Engine roughness threshold value consists of base value, which is determined by a load/speed dependent map. During warm-up, a coolant temperature dependent correction value is added. In case of multiple misfiring, threshold is reduced by an adjustable factor. Without sufficient sensor wheel adaptation, engine roughness threshold is limited to a speed dependent minimum value. A change of threshold toward a smaller value is limited by a variation constant.
3. Determination Of Misfiring - Misfire detection is performed by comparing engine roughness threshold value with engine roughness value. If a misfire event is detected in a cylinder, misfire detection of next cylinder in firing order is deactivated to prevent a faulty diagnosis. Fault Processing Statistics - Within an interval of 1000 crankshaft revolutions, detected misfiring events are added for each cylinder. If sum of all cylinder misfire incidents exceeds a predetermined value, fault code for emission relevant misfiring is preliminarily stored. If only one cylinder is misfiring, a cylinder selective fault code is stored. If more than one cylinder is misfiring, fault code for multiple misfiring is also stored. Within an interval of 200 crankshaft revolutions, detected number of misfiring events is weighted and calculated for each cylinder. Weighting factor is determined by a load/speed dependent map. If sum of cylinder misfire incidents exceeds a predetermined value, fault code for indicating catalyst damage relevant misfiring is stored and MIL is illuminated at once. If cylinder selective count exceeds predetermined threshold, following measures take place: Lambda closed loop system is switched to open-loop. Cylinder selective fault code is stored. If more than one cylinder is misfiring, fault code for multiple misfire is also stored. Fuel supply to respective cylinder is cut off. Counters are reset after each interval. (Scheme 238)

Scheme 239

Scheme 240

1. General Description Measure Principle - Method of engine misfire detection is based on monitoring crankshaft acceleration. Engine roughness is derived from differences from segment periods (90 degree crank angle) duration which are corrected and compared to a load and engine-speed dependent thresholds. Different statistical methods are used to distinguish between normal changes of segment duration and changes due to misfire. (Scheme 239) Segment periods are measured through an angular range of 90 degree crank angle. The segment starts 54 degrees before TDC. Beginning and end of the segments are located at the same angle. Duration of crankshaft segments is measured continuously. Sensor Wheel Adaptation - To eliminate manufacturing tolerances and off-center installation, adaptation of sensor wheel tolerances is carried out during fuel cut-off. Segment periods are corrected by adaptation values. With progressing adaptation, sensitivity of misfire detection is increasing. Calculation Of Engine Roughness Threshold Value - Engine roughness threshold value consists of base value, which is determined by a load/speed dependent map. During warm-up, base value is multiplied by a coolant temperature dependent correction value. Without sufficient sensor wheel adaptation, engine roughness threshold is limited depending on wheel tolerances expected.
2. Misfire Monitoring Structure - (Scheme 237)
3. Fault Processing - (Scheme 240) Error Window - Within an interval of 200-1000 crankshaft revolutions, "error windows" to check for similar engine conditions are determined. Upon detection of misfire, window is extended if current operating point is not within window. Engine Operating Point Window - Engine operating window is updated with each segment without misfire. Misfire Detection (Emission Increase) - Within an interval of 1000 crankshaft revolutions (4000 segments), detected misfire events are added for each cylinder. If sum of all cylinder misfire incidents exceed a predetermined value, a fault code is stored. If more than one cylinder is misfiring, all misfiring cylinders will be specified and individual fault codes for all misfiring cylinders and for multiple cylinder will be stored. Misfire Detection (Catalyst Damage) - Within an interval of 200 crankshaft revolutions, detected number of misfiring events is weighted and calculated for each cylinder. Weighting factor is determined by a load/speed dependent map. If sum of cylinder misfire incidents exceeds a predetermined value, a fault code is stored and MIL is illuminated. If cylinder selective count exceeds predetermined threshold, following measures take place: Lambda closed loop system is switched to open-loop. Cylinder selective fault code is stored. If more than one cylinder is misfiring, fault codes for all individual cylinders and for multiple cylinders will be stored. Fuel supply to respective cylinder is cut-off.

Evaporative Emissions

Control of evaporative fuel vapors (hydrocarbons) from fuel tank is important for overall reduction in vehicle emissions. Evaporative system has been combined with ventilation of fuel tank, which allows tank to breathe (equalization). The overall operation provides

1. An inlet vent, to an otherwise "sealed" fuel tank, for the entry of air to replace the fuel consumed during engine operation.
2. An outlet vent with a storage canister to "trap and hold" fuel vapors that are produced by the expansion/evaporation of fuel in the tank, when the vehicle is stationary.

Canister is then "purged" using engine vacuum to draw the fuel vapors into the combustion chamber. This "cleans" the canister allowing for additional storage. Like any other form of combustible fuel, the introduction of these vapors on a running engine must be controlled. The ECM(s) control the evaporative emission valves which regulate purging of evaporative vapors. See

(Scheme 241)

Scheme 241

On-Board Refueling Vapor Recovery (ORVR)

ORVR system recovers and stores hydrocarbon fuel vapor during refueling. Non-ORVR vehicles vent fuel vapors from the tank venting line back to the filler neck and in many states reclaimed by a vacuum receiver on the filling station fuel pump nozzle. When refueling, the pressure of the fuel entering the tank forces the hydrocarbon vapors through the tank refuelling breather hose to liquid/vapor expansion tank and into the active charcoal canister. HC vapors are stored in active charcoal canister and the system can then "breathe" through Diagnostic Module Tank Leakage (DMTL) and air filter.

Scheme 242

Scheme 243

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Scheme 249

1. Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of.039" (1.0 mm) and greater. Using a Leak Detection Pump (LDP), a vacuum actuated pump located at the atmospheric connection of the evaporative canister, a pressure test of the evaporative system is performed in the following order: During the fast pulse phase the evaporative system is set under a defined pressure. The pressure in the evaporative system after the fast pulse phase may be higher or lower than the defined pressure depending on fuel level in tank. Natural frequency phase that follows past pulse phase is therefore needed to adjust pressure to its correct value. During final measurement phase, time between pump strokes of LDP is evaluated. In case of a time between pump strokes below a preset threshold, a leak is assumed to be present. During pressure test, purge valve needs to be shut. After test canister purge is resumed, remaining pressure in evaporative system is bled off. To have maximum capacity (or minimal loss of purge air due to leak detection) test normally runs after engine cold start. However, under certain circumstances, test may be preliminary aborted and started again later during engine run if all conditions for restart of test are met.
2. Monitoring Structures Of Leak Measurement (LDP) Cold Start Conditions - At time of engine start, value of intake air temperature monitor (TAL REF monitor) is initialized to maximum possible value. If a specified load and a specified vehicle speed is exceeded over a specific time, value of TAL REF is updated with value provided by intake air temperature sensor. This is only done if intake air temperature value is lower than value that is already represented by TAL REF. Therefore, TAL REF always represents minimum value of intake air temperature sensor found during conditions mentioned above. Using this technique, following sequences are possible: Cold Start Conditions - Monitoring Structure - (Scheme 242) Cold Start Conditions - Use Of Ambient Temperature Signal Provided By Vehicle Can Bus - Leak measurement (LDP) component is specified for defined temperature range. To prevent component from being operated under unspecified conditions, ambient temperature is used as a condition for starting monitoring sequence after cold start. Ambient temperature signal is checked for circuit continuity later in driving cycle by means of intake air temperature monitor (TAL REF monitor). At time of engine start, value of intake air temperature monitor (TAL REF monitor) is initialized to maximum possible value. If a specified load and a specified vehicle speed is exceeded over a specific time, value of TAL REF is updated with value provided by intake air temperature sensor. This is only done if intake air temperature value is lower than value that is already represented by TAL REF. Therefore, TAL REF always represents minimum value of intake air temperature sensor found during conditions mentioned above. Using this technique, following sequences are possible: Ambient temperature is within specified range and no leak is detected during monitor sequence: in this case system is considered to be without a leak and no fault code is stored. Ambient temperature is within specified range and a leak is detected during monitoring sequence: After conditions for updating intake air temperature monitor (TAL REF monitor) are met and TAL REF is within specified range, a fault code is stored. In case TAL REF is out of specified range no fault code is stored. Ambient temperature is out of specified range at time of engine start. This leads to a preliminary cancellation of monitoring sequence. Monitoring sequence is carried out as soon as all conditions for repetition are met after a preliminary cancellation.
3. Condition For Preliminary Abort - Monitoring Structure - (Scheme 243)
4. Condition For Preliminary Abort - Downhill Run Detection LDP measures difference between the internal tank pressure and ambient pressure. In case of a vehicle moving downhill, internal tank pressure remains constant whereas ambient pressure increases. Consequently, pressure difference measured by LDP decreases which may cause detection of a leak that is not present (i.e. a false alarm). To prevent this, a downhill run detection that compares engine torque with a torque that is needed for driving the car on level terrain at a given speed, is implemented. Once a downhill run is detected, monitoring sequence is preliminary aborted. (Scheme 244)- (Scheme 247).
5. Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging.
6. Monitoring Structure Of Evaporative Purge System Flow Check - (Scheme 248) Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally.
7. Step 2 - For A Stoichiometric Mixture - In this case, lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function, several conditions have to be satisfied: Vehicle speed = 0. Engine at idle speed. Closed loop of lambda controller. Coolant temperature greater than fixed limit. Transmission in gear. In addition, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later. (Scheme 249)

Scheme 250

Scheme 251

Scheme 252

Scheme 253

Scheme 254

Scheme 255

Scheme 256

Scheme 257

Scheme 258

1. Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of.019" (0.5 mm) and greater. Using a Diagnostic Module Tank Leakage (DM TL), an electrically actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in the following order: During REFERENCE LEAK MEASUREMENT, electrically actuated pump delivers through reference restriction. Engine management system measures pump electrical current consumption in this section. (Scheme 250) During LEAK MEASUREMENT, electrical actuated pump delivers through charcoal canister into fuel-tank system. Pressure in evaporative system may be up to 25 kPa depending on fuel level in tank. Engine-management system measures pump electrical current consumption. A comparison of currents of reference leak measurement and leak measurement is a measure for leakage in tank. (Scheme 251) During PRESSURE TEST, purge valve needs to be shut. After test, canister purge is resumed and consequently remaining pressure in evaporative system is bled off. (Scheme 252)
2. Monitoring Structure Of Leak Measurement - (Scheme 253)- (Scheme 254).
3. Diagnosis Frequency & MIL Illumination - (Scheme 255)- (Scheme 256).
4. Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging.
5. Monitoring Cycle Of Evaporative Purge System Flow Check - (Scheme 257) Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally. Step 2 - For A Stoichiometric Mixture - In this case, lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function, several conditions have to be satisfied: Vehicle speed = 0. Engine at idle speed. Closed loop of lambda controller. Coolant temperature greater than fixed limit. In addition, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later. Engine idle speed variation is less than a fixed limit.
6. Evaporative System Leak Measurement With LDP (740i & 740iL) - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of 1.0 mm and larger. By means of a Leak Detection Pump (LDP), a vacuum actuated pump located at the atmospheric connection of the evaporative cane test of the evaporative system is performed in the following order: During FAST PULSE PHASE evaporative system is set under a defined pressure. Pressure in evaporative system after FAST PULSE PHASE may be higher or lower than defined pressure depending on fuel level in tank. NATURAL FREQUENCY PHASE that follows PAST PULSE PHASE is therefore needed to adjust pressure to its correct value. During final measurement, phase of time between pump strokes of LDP is evaluated. In case of a time between pump strokes below a preset threshold, a leak is assumed to be present. During pressure test, purge valve needs to be shut. After test canister purge is resumed and consequently the remaining pressure in evaporative system is bled off. To have maximum capacity (or minimal loss of purge air due to leak detection) test normally runs after engine cold start. However, under certain circumstances test may be preliminary aborted and started again later during engine run if all conditions for restart of test are met.
7. Monitoring Structures Of Leak Measurement (LDP) - Cold start conditions/monitoring structure. (Scheme 242)
8. Cold Start Condition: Use Of Ambient Temperature Signal Provided By Vehicle Can Bus (740i & 740iL) - The Leak Detection Pump (LDP) component is specified for defined temperature range. To prevent the component from being operated under unspecified conditions, ambient temperature is used as a condition for starting monitoring sequence after cold start. Ambient temperature signal is checked for circuit continuity later in driving cycle by means of intake air temperature monitor (TAL REF monitor): At the time of engine start the value of TAL REF is initialized to the maximum possible value. If a specified load and a specified vehicle speed is exceeded over a specific time the value of TAL REF is updated with the value provided by the intake air temperature sensor. This however is only done if the intake air temperature value is lower than the value that is already represented by TAL REF, Thus TAL REF always represents the minimum value of the intake air temperature sensor found during the conditions mentioned above. Using this technique the following sequences are possible: Ambient temperature is within specified range and no leak is detected during the monitor sequence. In this case, system is considered to be without a leak and no fault code is stored. Ambient temperature is within specified range and a leak is detected during monitoring sequence. After conditions for updating TAL REF are met and TAL REF is within specified range, a fault code is stored. In case TAL REF is out of specified range, no fault code is stored. Ambient temperature is out of specified range at time of engine start: This leads to a preliminary cancellation of the monitoring sequence, the monitoring sequence is carried out as soon as all conditions for repetition after a preliminary abort.
9. Condition For Preliminary Abort (740i & 740iL) - (Scheme 243)
10. Condition For Preliminary Abort, Downhill Run Detection (740i & 740iL) - The LDP measures the difference between the internal tank pressure and the ambient pressure. In case of a vehicle moving downhill the internal tank pressure remains constant whereas ambient pressure increases. Consequently, pressure difference measured by the LDP decreases which may cause the detection of a leak that is not present (i. e. false alarm). To prevent this, a downhill run detection that compares engine torque with a torque that is needed for driving the car on level terrain at a given speed, is implemented. Once a downhill run is detected, monitoring sequence is preliminary aborted. See. (Scheme 244), (Scheme 246), (Scheme 247) and (Scheme 258).
11. Evaporative Purge System Flow Check (740i & 740iL) - The purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging. (Scheme 248)

Scheme 259

Scheme 260

Scheme 261

Scheme 262

Scheme 263

Scheme 264

1. Evaporative System Leak Measurement - Evaporative system monitoring permits detection of leaks in evaporative system with a diameter of.039" (1.0 mm) and up. By means of a Diagnostic Module-Tank Leakage (DM-TL), a electrical actuated pump located at atmospheric connection of evaporative canister, a pressure test of evaporative system is performed in the following order: During REFERENCE LEAK MEASUREMENT, electrical actuated pump delivers through reference restriction. Engine management system measures pump electrical current consumption in this section. (Scheme 250) During LEAK MEASUREMENT, electrical actuated pump delivers through charcoal canister into fuel tank system. Pressure in evaporative system may be up to 25 kPa depending on fuel level in tank. Engine management system measures pump electrical current consumption. A comparison of currents of reference leak measurement and leak measurement is a measure for leakage in tank. (Scheme 251) During PRESSURE TEST, purge valve needs to be shut. After test canister purge is resumed, remaining pressure in the evaporative system is bled off. (Scheme 252)
2. Evaporative System Monitoring Structure - (Scheme 259)- (Scheme 260).
3. Diagnosis Frequency & MIL Illumination - see scheme 72- (Scheme 263).
4. Evaporative Purge System Flow Check - Purge flow from charcoal canister through purge valve is monitored after fuel system adaptation is completed and lambda controller is at closed loop condition. Diagnosis is started during regular purging. (Scheme 264)
5. Monitoring Cycle Of Evaporative Purge System Flow Check Step 1 - For Rich Or Lean Mixture - Flow through purge valve is assumed as soon as lambda controller is compensating for a rich or a lean shift. After this procedure, diagnosis is completed and evaporative purge system resumes working normally. Step 2 - For A Stoichiometric Mixture - In this case, lambda controller does not need to compensate for a deviation. Therefore, after finishing regular purging, purge valve is opened and closed abruptly several times. Effect of additional cylinder charge triggers a variation of engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed. To start diagnosis function (step 2) several conditions have to be satisfied: Vehicle speed = 0. Engine at idle speed. Closed loop of lambda controller. Coolant temperature greater than a fixed limit. Furthermore, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted and started again later. Engine idle speed variation less than a fixed limit.

SECONDARY AIR SYSTEM MONITORING

To reduce HC and CO emissions while engine is warming up, system uses a secondary air injection system. Immediately following a cold engine start, fresh air/oxygen is injected directly into the exhaust manifold. By injecting oxygen into exhaust manifold, warm up time of catalyst is reduced and oxidation of hydrocarbons is accelerated. Activation period of air pump can vary depending on engine type and operating conditions. See SECONDARY AIR SYSTEM MONITORING table.

SECONDARY AIR SYSTEM MONITORING

System components include electric air injection motor/pump, electric motor/pump relay, non-return valve, vacuum/vent valve, stainless steel air injection pipes, vacuum reservoir, vacuum reservoir check valve, and in-line resistor for speed control (V12 engine only).

Secondary air injection system is monitored via use of pre-catalyst oxygen sensor(s). Once air pump is active and is air injected into system, signal at oxygen sensor will reflect a lean condition. If oxygen sensor signal does not change within a predefined time, fault will be set and identify the faulty bank(s). If after completing the next cold start and a fault is again present, CHECK ENGINE light will be illuminated.

Test Group 1BMXV05.4LEV

General Description - At cold start the secondary air pump and valve are switched on for their normal operating function. The secondary air delivered into the exhaust gas is causing a lean mixture indicated by the output voltage of the oxygen sensor. At any time the oxygen sensor indicates a lean mixture within the maximum number of diagnosis, a counter is incriminated by "one" up to a predetermined value. This fixed limit corresponds to the minimum amount of secondary air (low-flow-limit-check). (Scheme 265)

Scheme 265

Test Groups 1BMXV04.4LEV & 1BMXT04.4E53

General Description - At cold start, secondary air pump and valve are switched on for their normal operating function. Secondary air delivered into exhaust gas causes a lean mixture indicated by output voltage of oxygen sensor. Anytime oxygen sensor indicates a rich mixture (voltage greater than a fixed limit) within a predetermined time range and calculation of relative secondary air mass is less than a defined threshold, secondary air system appears to be faulty. Now a correction procedure follows immediately, after secondary air system is switched off. Air/fuel influence is determined by deviation of lambda controller.

If influence is less than a fixed threshold, finally a fault will be detected. If influence is greater than a fixed threshold, results of diagnosis will be rejected as long as a lean mixture (voltage less than a fixed limit) is indicated from oxygen sensor within a predetermined time range and correction of air/fuel influence (after secondary air pump shuts-off) is less than a fixed threshold, a fault will also be detected. (Scheme 266)

Scheme 266

Test Group 1BMXV04.9S62

General Description - At cold start, secondary air pump and valve are switched on for their normal operating function. Secondary air delivered into exhaust gas is causing a lean mixture indicated by output voltage of oxygen sensor. Anytime oxygen sensor indicates a rich mixture (voltage greater than a fixed limit) within a predetermined time range and calculation of relative secondary air mass is less than a defined threshold, secondary air system is faulty. A correction procedure follows immediately after secondary air system is switched off. Air/fuel influence is determined by deviation of lambda controller. If influence is less than a fixed threshold, a fault will be detected. If influence is greater than a fixed threshold, results of diagnosis will be rejected as long as a lean mixture (voltage less than a fixed limit) is indicated from oxygen sensor within a predetermined time range and correction of air/fuel influence (after secondary air pump shuts-off) is less than a fixed threshold. A fault will also be detected. (Scheme 267)

Scheme 267

FUEL SYSTEM MONITORING

Fuel system monitoring is an OBD-II requirement which monitors calculated injection time in relation to engine speed, load, and the pre-catalytic converter oxygen sensor signals as a result of the residual oxygen in the exhaust stream. Engine control module uses the pre-catalyst oxygen sensor signals as a correction factor for adjusting and optimizing the mixture pilot control under all engine operating conditions.

Adaptation Values

To maintain an ideal air/fuel ratio, engine control module is capable of adapting to various environmental conditions encountered while the vehicle is in operation (i.e. changes in altitude, humidity, ambient temperature, fuel quality, etc.). Adaptation system can only make slight corrections and cannot compensate for large changes which may be encountered as a result of incorrect airflow or incorrect fuel supply to the engine.

Within areas of adjustable adaption, engine control module modifies injection rate during idle and low load mid range engine speeds (additive adaptation) and during operation under a normal to higher load when at higher engine speeds (multiplicative adaptation). These values are displayed in DIAGNOSIS REQUESTS section of DIS software and is a helpful diagnostic tool that shows how system is trying to compensate for a less than ideal initial air/fuel ratio. See DIAGNOSIS REQUESTS table.

Note. If adaptation value is greater than 0.0 ms, engine control module is trying to enrichen mixture. If adaptation value is less then 0.0 ms, engine control module is trying to lean mixture.

DIAGNOSIS REQUESTS

Scheme 268

Scheme 269

Scheme 270

1. Mixture Pilot Control - Air mass taken in by engine and engine speed are measured. These signals are used to calculate an injection signal. This mixture pilot control follows fast load and speed changes.
2. Lambda Controller - PCM compares oxygen sensor signal of sensor upstream of the catalyst with a reference value and calculates a correction factor for pilot control.
3. Adaptive Pilot Control - Drifts and faults in sensors and actuators of fuel delivery system as well as undetected air leakage influence pilot control. This causes increasing deviations of air/fuel ratio. Adaptive pilot control effects controller correction in 3 different ranges: fault additive per time unit, multiplicative fault and fault additive per injection.
4. Ranges Of Learning Correction Coefficients - Lambda deviations in range No. 1 are compensated by an additive correction value multiplied by an engine speed term. By this, an additive correction per time unit is created. Lambda deviations in range No. 2 are compensated by a multiplication factor. Lambda deviations in range No. 3 are compensated by an additive correction per injection cycle. A combination of all 3 ranges will be correctly separated and compensated. Each value is adapted in its corresponding range only. But each adaptive value corrects pilot control within whole load/speed range. At next start, stored adaptive values are included in calculation of pilot control just before closed loop control becomes active. (Scheme 268)
5. Diagnosis Of Fuel Delivery System - Faults in fuel delivery system can occur which cannot be compensated for by adaptive pilot control. In this case, adaptive values leave a predetermined range. If adaptive value is outside a plausible range, then MIL is illuminated and fault is stored. (Scheme 269)- (Scheme 270).

Scheme 271

1. General Description - Fuel system monitoring includes lambda controller restriction against limits for rich and lean and permanent deviation from mean position.
2. Monitoring Structure - If fuel system is suddenly hard disturbed and therefore lambda controller reaches restriction (lean limit), a timer is started. Timer is incriminated as long as controller remains at limit. If it exceeds a predetermined value, a fault for short trim will be detected and stored for rich and lean exceeding separately. For permanent deviation from mean position, there are additional lean and rich thresholds. If accumulated time (sum of all excesses for rich or lean) is greater than a fixed limit during a defined period, a fault for long term trim will be detected and stored for rich and lean exceeding separately. (Scheme 271)

OXYGEN SENSOR MONITORING

Note. Testing oxygen sensor should be performed using oscilloscope from PRESET MEASUREMENT list. If signal remains high (rich condition) check: fuel injectors, fuel pressure, ignition system, input sensors that influence air/fuel mixture, and engine mechanical. If signal remains low (lean condition) check: air/vacuum leak, fuel pressure, input sensor that influences air/fuel mixture, and engine mechanical. A mixture related fault code should be investigated first and does not always indicate a defective oxygen sensor. (Scheme 272)

Scheme 272

For oxygen sensor to operate correctly, sensor element must be heated. A non-operating heater will not allow sensor signal to reach its predefined maximum and minimum thresholds, resulting in delayed closed loop operation causing an impact on emission levels. As part of monitoring function for heater current and voltage, circuit is also checked for an open, short to ground and short to voltage, depending on values of current or voltage being monitored. See OXYGEN SENSOR MONITORING CONDITIONS table.

On Bosch systems, heater monitoring function measures both sensor heater current and the heater voltage in order to calculate sensor heater resistance and power. Oxygen sensor heater current is calculated via a voltage drop over a shunt resistor, internal to control module. If power of heater is not within a specified range, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored continuously while vehicle is in closed loop operation, as long as heater is activated by PCM. See OXYGEN SENSOR VOLTAGE OPERATING RANGE table.

On Siemens systems, if heater output is too low, signal amplitude of oxygen sensor will be reduced. If minimum low (rich) voltage and high (lean) voltage cannot be obtained within a predefined time, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function of pre-cat sensor is monitored continuously while vehicle is in closed loop operation, as long as heater is activated by PCM. See OXYGEN SENSOR VOLTAGE OPERATING RANGE table.

OXYGEN SENSOR MONITORING CONDITIONS

OXYGEN SENSOR VOLTAGE OPERATING RANGE

Oxygen Sensor Electrical Integrity Check

Monitoring electrical integrity of oxygen sensor is an ongoing functional check made under normal vehicle operation which pertains to faults with either the wiring, connectors, or sensor. If the monitored sensor voltage exceeds maximum threshold value, DME will interpret signal as a short to voltage. If the monitored sensor voltage is below the minimum threshold value the DME will interpret the signal as a short circuit or a short to ground. If the monitored voltage of the sensor remains unchanged or within a predetermined voltage range after the sensor has been heated and the engine temperature has exceeded a predefined threshold, the DME will interpret the signal as an open. (Separate fault code set - Siemens only). See OXYGEN SENSOR ELECTRICAL CHECK table.

OXYGEN SENSOR ELECTRICAL CHECK

Oxygen Sensor Heater Check

In order for the oxygen sensor to operate correctly the sensor element must be heated. An improperly/non operating heater will not allow the sensor signal to reach its predefined maximum and minimum thresholds which can result in delayed closed loop operation causing an impact on emission levels, or in increased emission levels while in closed loop operation. As part of the monitoring function for heater current and voltage, circuit is also checked for an open, short to ground and short to voltage depending on values of current or voltage being monitored.

On Bosch systems, heater monitoring function measures both sensor heater current and heater voltage in order to calculate sensor heater resistance and power. Oxygen sensor heater current is calculated via a voltage drop over a shunt resistor, internal to control module. If power of heater is not within a specified range, a fault will be set. The next time the heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored continuously while vehicle is in closed loop operation, as long as the heater is activated by the Engine Control Module.

On Siemens systems, if heater output is too low, signal amplitude of oxygen sensor will be reduced. If predetermine minimum low (rich) voltage and high (lean) voltage can not be obtained within a predefined time, a fault will be set. Next time heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function of pre-cat sensor is monitored continuously while the vehicle is in closed loop operation, as long as the heater is activated by the Engine Control Module.

Siemens Post-Catalyst Heater

Rear oxygen sensor heater is evaluated by monitoring the amount of change that occurs on rear oxygen sensor signal during deceleration/fuel cut-off phase. During deceleration phase, post-cat oxygen sensor is switched to a load resistance value of 100 kW (normal sensor resistance is 30 kW). By switching the resistance of the sensor to 100 kW, sensor voltage is expected to remain within a fixed range (lean). If heater is operating correctly, oxygen sensor signal will remain within a predefined voltage range.

System monitors number of cycles for which sensor voltage remains within fixed range (once per diagnostic cycle). If length of time sensor remains within fixed range is less then predetermined limit, fault will be set. During next drive cycle if heater circuit is monitored and a fault is again present, CHECK ENGINE light will be illuminated. Heater function is monitored once per trip while vehicle is in closed loop operation.

Scheme 273

Scheme 274

Scheme 275

Scheme 276

1. General Description - Response rate of upstream oxygen sensor is monitored by measuring period of lambda control oscillations. (Scheme 273)- (Scheme 274).
2. Diagnosis Procedure Of Monitor Sensor (Downstream) - Activity of monitor sensor after reaching operating conditions, is determined by 2 different procedures: Oscillation Check (Line Crossing) - If following checks are correct, monitor sensor will be regarded as okay: Monitor sensor signal (sensor voltage) is equal to or greater than nominal value of TV-correction and voltage increases, if lambda control goes to the lean side. Monitor sensor signal (sensor voltage) is less than nominal value of TV-correction and voltage decreases, and if lambda control goes to rich side. Fuel Cut-Off Check - In addition to above mentioned checks, signal behavior of monitor sensor is checked in case of fuel cut-off. Therefore, monitor sensor voltage has to be below a given nominal value in case of fuel cut-off. If monitor sensor detected a defect, a fault code is stored and MIL is illuminated at next driving cycle.
3. Oxygen Sensor Heater Monitoring (Up & Downstream) General Description - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures heater current for both sensors (voltage drop over a shunt) and heater voltage (heater supply voltage) to calculate sensor heater resistance. Monitoring function is activated once per trip if heater has been switched on for a certain time period and current has stabilized. (Scheme 275)
4. Oxygen Sensor Circuit Monitoring - Monitoring of electrical faults of sensors upstream and downstream of catalyst-not plausible voltages: Voltages exceeding maximum threshold are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to ECM ground. (Scheme 276)
5. If there is no plausible course of sensor voltage, an open circuit of sensor upstream catalyst can be detected if voltage remains in a specified range after sensor has been heated.

Scheme 277

Scheme 278

1. The response rate of the upstream oxygen sensor is monitored by measuring the period of the lambda control oscillations. (Scheme 273)- (Scheme 274). For diagnosis procedure of monitor sensor (downstream), activity of monitor sensor after reaching operating conditions is determined by 2 different procedures: Oscillation Check (Line Crossing) - If following checks are correct, monitor sensor will be regarded as okay. The monitor sensor signal (sensor voltage) is greater than or equal to the nominal value of the TV correction and voltage increases, or if lambda control goes to the lean side. Monitor sensor signal (sensor voltage) is less than nominal value of TV correction and voltage decreases, or if lambda control goes to the rich side. Fuel Cut-Off Check - In addition to above mentioned checks, signal behavior of monitor sensor is checked in case of fuel cut-off. Therefore, monitor sensor voltage has to be below a given nominal value in case of fuel cut-off. If monitor sensor is detected defective by OSCILLATION CHECK or FUEL CUT-OFF CHECK, a fault code is stored and MIL is illuminated at next driving cycle.
2. Oxygen Sensor Heater Monitoring (Up/Downstream) - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures both sensor heater current (voltage drop over a shunt) and heater voltage (heater supply voltage) to calculate sensor heater resistance. Monitoring function is activated once per trip if heater has been switched on for a certain time and current has stabilized. (Scheme 277)- (Scheme 278).
3. Oxygen Sensor Circuit Monitoring - Monitoring of electrical faults of sensors upstream and downstream of catalyst. Implausible voltages are voltages exceeding the maximum threshold and are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to ECM ground. Implausible cause of sensor voltage is an open circuit if sensor upstream catalyst can be detected, or if voltage remains in a specified range after sensor has been heated.

Scheme 279

Scheme 280

Scheme 281

Scheme 282

1. Monitoring Upstream Oxygen Sensor - Both oxygen sensors upstream from the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). (Scheme 279)
2. Monitoring Structure Of Upstream Oxygen Sensor - (Scheme 280)
3. Monitoring Procedure Of Upstream Oxygen Sensor; Overall Period Time Monitoring Of Upstream Oxygen Sensor - This determines the switching time the lean and rich period times are added during a fixed number of lambda controller cycles. A malfunction is registered if one or both of the times exceed the thresholds which depend on engine speed and load. (Scheme 281)- (Scheme 282).
4. Monitoring Procedure Of Downstream Oxygen Sensors (Rich To Lean Intake Mixture) - Lean sensor voltage is used to diagnose sensor activity. Therefore, this check is performed during deceleration fuel cut-off. Diagnosis starts after a calculated air mass (integral) is reached at transient from any operation mode to fuel cut-off mode and a defined time in deceleration fuel cut-off. Sensor voltage has to drop below a predetermined value otherwise a fault is detected and a code is stored.
5. Monitoring Procedure Of Downstream Oxygen Sensors (Lean To Rich Intake Mixture) - When diagnostic conditions at deceleration fuel cut-off are not fulfilled, diagnosis is carried out in opposite direction of oxygen sensor voltage. For a positive diagnosis result, signal must overrun a threshold after deceleration fuel cut-off. To ensure diagnosis, mixture can be short-term enriched, independent of respective operating conditions.
6. Oxygen Sensor Heater Monitoring - For proper function of oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures continuously both sensor heater current as well as heater voltage (heater supply voltage) to calculate sensor heater resistance. (Scheme 277)- (Scheme 278).
7. Oxygen Sensor Circuit Monitoring - Monitoring electrical faults of sensors upstream and downstream of catalyst. Non-plausible voltages: Voltages exceeding maximum threshold are caused by a short circuit to voltage. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to PCM ground. A non-plausible course of sensor voltage indicates an open circuit of sensor upstream catalyst can be detected if voltage is remaining in a specified range after sensor has been heated.

See also:
• BASIC DIAGNOSTIC PROCEDURES
• TROUBLE SHOOTING - NO CODES
• ENGINE MANAGEMENT SYSTEM IDENTIFICATION
• TEST GROUP IDENTIFICATION
• CATALYST MONITORING
• MISFIRE MONITORING
• SECONDARY AIR SYSTEM MONITORING
• FUEL SYSTEM MONITORING
• OXYGEN SENSOR MONITORING
• 1BMXV05.4LEV
• 1BMXV04.9S62
• 1BMXV04.4LEV & 1BMXT04.4E53