Diagnostic Trouble Codes with Test Charts BMW Z3 E36

INTRODUCTION

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed with self-diagnostics. BMW vehicles are equipped with 2 separate self-diagnostic systems. OBD-II self-diagnostic system accesses Diagnostic Trouble Codes (DLCs) using a generic scan tool connected to vehicle Data Link Connector (DLC). (Scheme 1)- (Scheme 3). BMW self-diagnostic system accesses DTCs using special BMW hardware and software connected to BMW engine diagnostic connector socket. (Scheme 4)

Regardless of self-diagnostic system, DME/Motronic 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 1997 MODEL COVERAGE table. These substitute values are canceled when normal engine operation is resumed.

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 1

Scheme 2

Scheme 3

Scheme 4

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 TESTS W/O 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.

1997 MODEL COVERAGE

CHECK ENGINE LIGHT

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

Scheme 5

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 5)
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 several different types of diagnostic hardware: the Mobile Diagnostic Computer (MoDiC), Diagnostic Information System Plus (DISplus) and the newer Group Tester One (GT-1). See ON-BOARD DIAGNOSTICS .

MoDiC System

The BMW MoDiC diagnostic system was developed to meet the diagnostic needs of BMW vehicles. It compliments the DIS tester as a diagnostic tool that enables the technician to quickly troubleshoot electronic faults and problems with the vehicles. The advantage of the MoDiC is its mobility. The tester can go anywhere in the workshop and to the vehicle. It can remain connected to the vehicle while it is driven to check for intermittent problems or conditions that only occur while the vehicle is driven. The MoDiC is a personal computer with interchangeable batteries, UNIX operating system, 3 gigabyte hard drive for data/program storage, 32 MB working memory, 90 megahertz Pentium processor, Diagnosis Information System (DIS), Technical Information System (TIS), Digital Multimeter, Counter, and single channel oscilloscope. Objectives used in the development of the MoDiC included maximum functional efficiency and mobility in the workshop, diagnostic procedures similar to the DIS, operation similar to the DIS, basic measurement techniques available, integrated TIS function, common software CD for both the MoDiC and DIS.

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. Also included is 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. If using a BMW scan tool, 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 6) 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. See TEST GROUP IDENTIFICATION. 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 6

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/MoDIC or GT-1. BMW codes determine diagnostic output for BMW DIS Plus/MoDIC 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/MoDIC/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/MoDIC/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. See .

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 1)- (Scheme 3). 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 (Scheme 5)

SUMMARY

If no hard DTCs are present, driveability symptoms exist or intermittent DTCs exist, proceed to TESTS W/O 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 sometimes 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. For additional diagnosis, see TEST GROUP IDENTIFICATION .

Note. Diagnosis is not available for all DTCs.

DIAGNOSTIC TROUBLE CODE

TABLE A: BMW DIAGNOSTIC TROUBLE CODES - M3, 328i, 328is & 528i (6-CYLINDER)

TABLE B: BMW DIAGNOSTIC TROUBLE CODES - Z3 (6-CYLINDER)

TABLE C: BMW DIAGNOSTIC TROUBLE CODES - Z3, 318ti & 318i (4-CYLINDER - 9/96-12/96)

TABLE D: BMW DIAGNOSTIC TROUBLE CODES - Z3, 318ti & 318i (4-CYLINDER - 1/97-8/97)

TABLE E: BMW DIAGNOSTIC TROUBLE CODES - 540i, 740i, 740iL & 840Ci (V8)

TABLE F: BMW DIAGNOSTIC TROUBLE CODES - 750iL & 850Ci (V12)

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

COMPONENT LOCATIONS

For component location information, see ELECTRICAL COMPONENT LOCATIONS - M3 , ELECTRICAL COMPONENT LOCATIONS - Z3 , ELECTRICAL COMPONENT LOCATIONS - 318ti , ELECTRICAL COMPONENT LOCATIONS - 318 & 328 Series , ELECTRICAL COMPONENT LOCATIONS - 5 Series , ELECTRICAL COMPONENT LOCATIONS - 7 Series or ELECTRICAL COMPONENT LOCATIONS - 8 Series article.

CONNECTOR IDENTIFICATION

Depending on model, control module uses an 88-pin connector or a combination of a 9-pin, 24-pin, 40-pin or 52-pin connector. For control module connector identification (Scheme 30)- (Scheme 34).

Scheme 30

Control Module Connector Terminal Identification (9-Pin Connector). Scheme 31

Control Module Connector Terminal Identification (24-Pin Connector). Scheme 32

Control Module Connector Terminal Identification (40-Pin Connector). Scheme 33

Control Module Connector Terminal Identification (52-Pin Connector). Scheme 34

TEST GROUP IDENTIFICATION

BMW supplies test group information in the following 6 categories

1. «CATALYST MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)
2. «MISFIRE MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)
3. «EVAPORATIVE SYSTEM MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)
4. «SECONDARY AIR SYSTEM MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)
5. «FUEL SYSTEM MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)
6. «OXYGEN SENSOR MONITORING»(/bmw/z3/e36-1995-2000/remont/testing-diagnostics/#diagnostic-trouble-codes-with-test-charts)

Specific engine family test group identification number (

for example: WBMXV02.8M52

) 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

Test Group VBM1.9VJGFEK & VBM1.9VJGKFK

General Description - Catalyst monitoring is based on monitoring its oxygen storage capability. Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by oxygen storage activity of catalyst. Amplitude of remaining lambda oscillations downstream of catalyst indicates storage capability. In order to determine catalyst efficiency, amplitude ratio of signal oscillations of upstream and downstream lambda sensors are compared. This information is evaluated separately in different engine load and speed ranges. If there is an indication of low storage capability in a certain number of operating ranges, a defective catalyst is recognized. (Scheme 35)- (Scheme 36).

Computation Of Amplitude Ratio - The 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 the 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. Variations like an increase of control frequency affect both signal paths in the same way and are compensated by the division.

Post Processing - Actual amplitude ratio is compared with a limit value according to load and speed range engine is operating in. Result of this comparison, difference of both values, is accumulated separately for each range. Therefore, even short time periods of driving in a certain range yield additional information. By using separate load and speed ranges in combination with accumulation of information, a monitoring result can be obtained during an FTP cycle.

Fault Evaluation - Accumulated information about 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 a fixed map value, a fault is detected and an internal fault flag will be set. If fault is detected again in next trip, MIL will be illuminated.

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 (such as fuel cut-off). During such periods, and for a certain time afterward, computations of amplitude values and post processing is halted. Therefore, a distortion of monitoring information is avoided.

Scheme 35

Scheme 36

Test Group VBM2.8VJGKEK & VBM2.8VJGKFK

Catalyst Monitoring General Description - Catalyst monitoring is based on monitoring its oxygen storage capability. The engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by the oxygen storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream of the catalyst indicates the storage capability.

1. Monitoring Procedure - In order to determine the efficiency the lean and rich time periods of the oxygen sensors up and downstream will be compared. (Scheme 37) The smaller of the two ratios determined is used for further processing. The cycle counter is incremented by one after each cycle. If the counter reaches a predetermined number of checks (235 lambda controller cycles) and the sum of all ratios determined is greater than a fixed value a fault will be stored in the computer memory. The monitoring procedure is then terminated until the engine is shut-off and started again.
2. Monitoring Structure - (Scheme 38)
3. Block Diagram Of System - (Scheme 39) NOTE: The conversion efficiency of both catalyst systems (Cyl. 1-3 and Cyl. 4-6) are separately monitored.

Scheme 37

Scheme 38

Scheme 39

Test Group VBM4.4VJGFEK & VBM5.4V8GFEK

Catalyst Monitoring General Description - Catalyst monitoring is based on monitoring catalyst's oxygen storage capability. Engine closed loop feedback control generates lambda (air/fuel ratio) oscillations in the exhaust gas. These oscillations are dampened by the oxygen storage activity of the catalyst. The amplitude of the remaining lambda oscillations downstream of the catalyst indicates storage capability. In order to determine catalyst efficiency the amplitude ratio of the signal oscillations of upstream and downstream lambda sensors are compared. This information is evaluated separately in different engine load and speed ranges. If there is an indication of low storage capability in a certain number of operating ranges, a defective catalyst is recognized.

Monitoring Structure

1. Catalyst Monitoring Structure - For catalyst monitoring structure flow chart and block diagram of system operation (Scheme 35)and (Scheme 36).
2. Computation Of The Amplitude Ratio - The first step in catalyst monitoring is computation of the amplitude of the signal oscillations of the lambda sensor upstream versus downstream of the catalyst. This is accomplished by extracting the oscillating signal component, computing the absolute value and averaging over time. The quotient of downstream amplitude value divided by upstream amplitude value is called Amplitude Ratio (AR). AR is the basic information necessary for catalyst monitoring. It is computed continuously over certain engine and speed ranges. The signal paths for both sensor signals are identical. Thus variations like an increase of the control frequency affects both signal paths in the same way and are compensated by the division.
3. Postprocessing - The actual AR is compared with a limit value according to the load and speed range the engine is operating in. The result of this comparison, the difference of both values, is accumulated separately for each range. Thus, 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 AR becomes more and more reliable as different load and speed ranges are used during a driving cycle. If the AR is greater than fixed map values a fault is detected and an internal fault flag will be set. If the fault is detected again in the next trip the MIL will be illuminated.
5. Check Of Monitoring Conditions - The monitoring principle is based on the detection of relevant oscillations of the downstream sensor signal during regular lambda control. It is necessary to check the driving conditions for exceptions where no regular lambda control is possible, e.g. fuel cut-off. During such periods, and for a certain time afterwards, the computations of the amplitude values and the postprocessing is halted. Thus, a distortion of the monitoring information is avoided.

Test Groups VBM1.9VJGFEK & VBM1.9VJGKFK

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 two ignition events, which is a measure for mean value of speed of this angular segment. This means a change of engine torque results in a change of engine speed. Additionally, influence of load torque will be determined. This means influences of different road surfaces (pavement, pot holes etc.). If mean engine speed is measured, influences caused by road surfaces have to be eliminated. 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, and fault processing counting procedure of single misfire events. (Scheme 40)

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, instead of misfire detection, 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 the engine roughness.

Misfire Detection - The 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 Multiple Misfiring - If several cylinders are misfiring (alternating one combustion/one misfire event), calculated engine roughness values may be that low, so that threshold is not exceeded during misfiring and therefore misfiring would not be detected. Based on this fact, 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. Degree of misfire evaluated in 1000 revolutions increments which would cause a durability demonstration vehicle to fail an inspection and maintenance program tailpipe emission test is 20 percent.

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.

Determination Of Misfiring - Misfire detection is performed by comparing engine roughness threshold value with engine roughness value.

Statistics & Fault Processing - 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 preliminary 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 (blinking). If cylinder selective count exceeds predetermined threshold, following measures take place: lambda closed loop system is switched to open-loop and 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. All misfire counters are reset after each interval. (Scheme 41)

Scheme 40

Scheme 41

1. Misfire Monitoring General Description Measure Principle - Method of engine misfire detection is based on monitoring crankshaft acceleration. Engine roughness is derived from differences from segment periods (120 degree crank angle) durations 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 42) Segment periods are measured through an angular range of 120 degree crank angle. The segment starts 78 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 increased. 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 - For misfire monitoring flow chart (Scheme 40)
3. Fault Processing - For fault processing flow chart (Scheme 43) 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 the 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 (3000 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. 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 immediately. 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. All misfire counters are reset after each interval.

Scheme 42

Scheme 43

Misfire Monitoring General Description - The method of engine misfire detection is based on evaluating the engine speed fluctuations. 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. Additionally the influence of the load torque will be determined. This means, the influences of different road surfaces, 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 the following main parts

1. Data acquisition, adaptation of sensor wheel is included.
2. Calculation of engine roughness.
3. Comparison with a threshold depending on operating points.
4. Some extreme conditions, during which misfire detections should be disabled for a short time.
5. Fault processing, counting procedure of single misfire events.

1. Misfire Monitoring Structure - For misfire monitoring structure flow chart (Scheme 44)
2. Data Acquisition - The duration of the crankshaft segments is measured continuously for every combustion cycle.
3. 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 increased. The adaptation values are stored in a non-volatile memory and taken into consideration for the calculation of the engine roughness.
4. Misfire Detection - The following operating steps are performed for each measured segment corrected by the sensor wheel adaptation: 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. Detecting Of Multiple Misfiring - If several cylinders are misfiring (e.g. alternating one combustion/one misfire event) the calculated engine roughness values may be that low, so that the threshold is not exceeded during misfiring and therefore misfiring would not be detected. Based on this fact, the periodicity of the engine roughness value is used as additional information during multiple misfiring. The engine roughness value is filtered and a new multiple filter value is created. If this filter value increases due to multiple misfiring, the roughness threshold is decreased. By applying this strategy, multiple misfiring is detected reliably. Calculation Of The Engine Roughness Threshold Value - The engine roughness threshold value consists of the 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 the threshold is reduced by an adjustable factor. Without sufficient sensor wheel adaptation the engine roughness threshold is limited to a speed dependent minimum value. A change of the threshold towards a smaller value is limited by a variation constant.
5. Determination Of Misfiring - Misfire detection is performed by comparing the engine roughness threshold value with the engine roughness value. If a misfire event is detected in a cylinder, the misfire detection of the next cylinder in firing order is deactivated to prevent a faulty diagnosis.
6. Statistics (Fault Processing) - Within an interval of 1000 crankshaft revolutions the detected misfiring events are added for each cylinder. If the sum of all cylinder misfire incidents exceeds a predetermined value, the 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, the fault code for multiple misfiring is also stored. (Scheme 41) Within an interval of 200 crankshaft revolutions the detected number of misfiring events is weighted and calculated for each cylinder. The weighting factor is determined by a load/speed dependent map. If the sum of cylinder misfire incidents exceeds a predetermined value the fault code indicating catalyst damage relevant misfiring is stored and the MIL is illuminated at once (blinking). If the cylinder selective count exceeds the predetermined threshold the following measures take place: The lambda closed loop system is switched to open loop. The cylinder selective fault code is stored. If more than one cylinder is misfiring, the fault code for multiple misfire is also stored. The fuel supply to the respective cylinder is cut-off. All misfire counters are reset after each interval.

Scheme 44

Test Group VBM1.9VJGFEK

General Description - 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 45)

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.

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 by a variation of the engine idle speed. A predetermined value is reached if system functions properly and diagnosis procedure is completed.

Scheme 45

Test Group VBM1.9VJGKFK

General Description - Evaporative system monitoring permits detection of leaks in evaporative emission control system with a diameter of .039" (1 mm) and greater. Evaporative emission control system is hermetically sealed off from atmosphere by means of a shut-off valve at charcoal canister. When purge valve opens, engine generates a vacuum in the tank. After closing purge valve, pressure increase is measured by a tank pressure sensor. If vacuum increases above a defined threshold, a leak is detected. As part of the vacuum, check purge flow is verified.

Monitoring Structure - Following conditions must be fulfilled to start monitoring procedure: no malfunction in detecting battery voltage, in detecting vehicle speed, in detecting air mass meter, in detecting coolant temperature, in detecting purge valve signal, in detecting throttle valve position sensor, in detecting idle speed control valve, in detecting shut off valve signal, misfire detection, tank pressure sensor, and secondary air system. (Scheme 46)- (Scheme 50).

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

Test Group VBM2.8VJGKFK

Evaporative System Monitoring General Description - The evaporative system monitoring permits the detection of leaks in the evaporative emission control system with a diameter of 1 mm and up. (Scheme 51)

The evaporative emission control system is hermetically sealed off from the atmosphere by means of a shut-off valve at the charcoal canister. When the purge valve opens, the engine generates a vacuum in the tank. After closing the purge valve, pressure increase is measured by a tank pressure sensor. If vacuum increases above a defined threshold a leak is detected. As part of the vacuum check, purge flow is verified. For vapor generation test and EVAP system diagnosis (Scheme 52)- (Scheme 55).

Scheme 51

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Test Group VBM2.8VJGKEK

Evaporative System Monitoring General Description - The evaporative system monitoring permits the detection of leaks in the evaporative emission control system with a diameter of 1 mm and up. (Scheme 51)

The evaporative emission control system is hermetically sealed off from the atmosphere by means of a shut-off valve at the charcoal canister. When the purge valve opens, the engine generates a vacuum in the tank. After closing the purge valve, pressure increase is measured by a tank pressure sensor. If vacuum increases above a defined threshold a leak is detected. As part of the vacuum check, purge flow is verified. For vapor generation test and EVAP system diagnosis (Scheme 52)- (Scheme 55).

EVAP Purge System Flow Check - Purge flow from the charcoal canister through the purge valve is monitored after the coolant temperature has reached a fixed minimum value. Diagnosis is started during regular purging.

Scheme 56

1. Monitoring Process Step 1 (For Rich Or Lean Mixture) - Flow through the purge valve is assumed as soon as the lambda controller is compensating for a rich or a lean shift. After this procedure the diagnosis is completed, and the evaporative purge system resumes working normally. (Scheme 56) Step 2 (For Stoichiometric Mixture, Or 1st Step Fails) - In this case the lambda controller does not need to compensate for a deviation. Therefore, after finishing the regular purging operation, the purge valve is opened and closed abruptly several times. The effect of additional cylinder charge, triggers a variation of engine idle speed. If a predetermined value is reached, the diagnosis procedure is completed. Step 3 (For Stoichiometric Mixture, Or 2nd Step Fails) - If the threshold at the 2nd step is not reached, an additional procedure is performed. The purge valve is opened and the idle air control valve is closed simultaneously to compensate the idle speed increase. The effect is a decrease of the measured idle air mass by the mass air flow sensor. If a predetermined value is reached, the diagnosis procedure is completed.

Test Group VBM4.4JGKEK & VBM5.4V8GFEK

Evaporative Purge System Monitoring General Description - Purge flow from the charcoal canister through the purge valve is monitored after fuel system adaptation is completed and the lambda controller is at closed loop condition. (Scheme 45) The diagnosis is started during one of two steps during regular purging.

1. Step 1 (For Rich Or Lean Mixture) - Flow through the purge valve is assumed as soon as the lambda controller is compensating for a rich or a lean shift. After this procedure the diagnosis is completed, and the evaporative purge system resumes working normally.
2. Step 2 (For Stoichiometric Mixture) - In this case the lambda controller does not need to compensate for a deviation. Therefore, after finishing the regular purging operation, the purge valve is opened and closed abruptly several times. The effect of additional cylinder charge, triggers a variation of engine idle speed. If a predetermined value is reached, the diagnosis procedure is completed.

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 an increase of lambda sensor signal until it reaches a predetermined value. This fixed limit corresponds to minimum amount of secondary air (low-flow-limit-check). (Scheme 57)

Check Conditions - To start diagnosis function, several conditions have to be satisfied: secondary air system on, no error from coolant temperature sensor, lambda sensor is heated up (stabilized condition), altitude driving conditions below 8000 feet, no error from evaporative system, no error from secondary air pump output stage, no error from battery voltage, no error from air mass sensor, no error from plausibility check of throttle valve and air mass sensor, and closed evaporative system purge valve. Furthermore, if diagnosis has already been started and one of the conditions has not been satisfied continuously, process will be interrupted.

Scheme 57

Check Procedure

1. Check conditions okay.
2. Start monitoring procedure.
3. Look at signal of lambda sensor before catalyst.

If signal is below threshold for definite times: system is set and monitoring procedure is ended. If signal is above threshold for definite times: store secondary air system fault and set cycle byte. If the fault is confirmed during the next driving cycle, MIL is illuminated.

Secondary Air System Monitoring 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. Any time the oxygen sensor indicates a lean mixture within the maximum time for monitoring, a counter is incremented by "one" up to a predetermined value. This fixed limit corresponds to the minimum amount of secondary air (low-flow-limit-check). For secondary air system monitoring flow chart (Scheme 58)

Scheme 58

General Description - Air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This mixture pilot control follows fast load and speed changes. ECM controller compares oxygen sensor signal of sensor upstream of catalyst with a reference value and calculates a correction factor for pilot control. (Scheme 59)

Adaptive Pilot Control - Drifts and faults in sensors and actuators of fuel delivery system as well as not measured air leakage influence pilot control. This causes increasing deviations of air/fuel ratio. Adaptive pilot control effects controller correction in 3 different ranges. Lambda deviations in range one 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 2 are compensated by a multiplication factor. Lambda deviations in range 3 are compensated by an additive correction per injection. 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 60)

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 61)

Scheme 59

Scheme 60

Scheme 61

Fuel System Monitoring General Description - Fuel system monitoring includes lambda controller restriction against limits for rich and lean and permanent deviation from mean position.

1. Monitoring Structure - If fuel system is suddenly hard disturbed and 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.
2. Monitoring Conditions - For monitoring conditions during closed loop (Scheme 62)

Scheme 62

1. Fuel System Monitoring General Description - Fuel system monitoring includes lambda controller restriction against limits for rich and lean and permanent deviation from mean position: Mixture Pilot Control - The air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This mixture pilot control follows fast load and speed changes. Lambda-Controller - The ECM-controller compares the oxygen sensor signal of the sensor upstream the catalyst with a reference value and calculates a correction factor for the pilot control.
2. Fuel System Monitoring Structure - Fuel system monitoring consists of following: Adaptive Pilot Control - Drifts and faults in sensors and actuators of the fuel delivery system as well as not measured air leakage influence the pilot control. This causes increasing deviations of the air/fuel ratio. The adaptive pilot control effects the controller on in three different ranges. (Scheme 59) Ranges Of Learning Correction Coefficients TRA, FRA & DTV - Lambda deviations in range 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 2 are compensated by a multiplication factor. Lambda deviations in range 3 are compensated by an additive correction per injection. A combination of all three ranges will be correctly separated and compensated. Each value is adapted in its corresponding range only. But each adaptive value corrects the pilot control within the whole load/speed range. At the next start the stored adaptive values are included in the calculation of the pilot control just before the closed loop control becomes active. (Scheme 60)
3. Fuel Delivery System Abbreviations - Fuel delivery system abbreviations are as follows: QU 1 - Upper air flow threshold range 1 NU 1 - Upper engine speed threshold range 1 TLARN - Upper engine load threshold f(n) range 2 TLL2 - Lower engine load threshold range 2 TRA - Additive per time unit learning correction coefficient (range 1) TRADN - Lower diagnosis threshold of TRA TRADX - Upper diagnosis threshold of TRA FRA - Multiplicative learning correction coefficient (range 2) FRADN - Lower diagnosis threshold of FRA FRADX - Lower diagnosis threshold of FRA DTV - Additive per revolution learning correction coefficient (range 3) DTVDN - Lower diagnosis threshold of DTV DTVDX - Upper diagnosis threshold of DTV QL2 - Lower air flow threshold range 2 QU3 - Upper air flow threshold range 3 NL3 - Lower engine speed threshold range 3 TLL3 - Lower engine load threshold range 3
4. Diagnosis Of Fuel Delivery System - Faults in the fuel delivery system can occur which cannot be compensated for by the adaptive pilot control. In this case the adaptive values leave a predetermined range. If the adaptive value is outside a plausible range, then the MIL is illuminated and the fault is stored. (Scheme 61)

General Description - Response rate of upstream oxygen sensor is monitored by measuring period of lambda control oscillations. (Scheme 63)

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 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 period and current has stabilized. (Scheme 64)- (Scheme 65).

Oxygen Sensor Circuit Monitoring - Oxygen sensor circuit monitors electrical faults of sensors upstream and downstream of catalyst. Implausible voltages are voltages exceeding maximum threshold (VMAX). Voltages falling below minimum threshold (VMIN) are caused by a short circuit of sensor signal or sensor ground to ECM ground. An open circuit of sensor upstream catalyst can be detected if voltage is remaining in a specified range after sensor has been heated. (Scheme 66)

Scheme 63

Scheme 64

Scheme 65

Scheme 66

Oxygen Sensor Monitoring General Description - 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 67)

1. Monitoring Procedure Switching Time - For monitoring the switching time, the time from lean to rich mixture and visa versa, are determined and compared with predetermined maximum values which depend on engine RPM and air mass. Relative thresholds (10-90% of min./max. amplitude) are used to determine the oxygen sensor switching time from lean to rich and visa versa. The sensor signals are monitored for reversal points while the switching times are being measured. If a reversal point is detected this oxygen sensor signal is not used to determine the switching time. (Scheme 68) Due to switching time fluctuations the results are averaged during the monitoring cycle (115 lambda control cycles) before comparing with the thresholds. Rich/Lean Periods - For determining 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(s) the thresholds which depend on engine speed and load. (Scheme 69)
2. Oxygen Sensor Heater Monitoring - For proper function of the oxygen sensor, the sensor element must be heated. A non functioning heater delays sensor readiness for closed loop control operation and influences emissions. Disconnection, short-to-ground and short-to-battery monitoring and oxygen sensor heater current and voltage monitoring are performed in the standard diagnosis function. Heater Circuit Oxygen Sensor Upstream - Due to slow sensor heating, in the case of low oxygen heating output, the rich voltage does not reach its maximum value within a defined time. This reduces the oxygen sensor signal amplitude which permits oxygen sensor heating output to be monitored. The malfunction detection is activated every 240 ms independent of engine operation. Oxygen Sensor Monitoring (Downstream Sensor) - Lean sensor voltage is evaluated for diagnosis of the heater circuit. Therefore this check is performed during deceleration/fuel cut-off phases. The sensor downstream must be switched to a load resistance of 100 k/ohms (normal operation 30 k/ohms). During this check, the oxygen sensor signal output voltage is controlled to a fixed value (lean limit). If the number of cycles during which the sensor signal lies within the defined limits is smaller than the limit, a fault will be stored. The sensor signal is checked every 20 ms during the heater circuit diagnosis.

Scheme 67

Scheme 68

Scheme 69

Oxygen Sensor Monitoring General Description - Both oxygen sensors upstream from the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring).

1. Monitoring Structure - (Scheme 63)
2. Flow Chart Of Monitoring Function - (Scheme 70)
3. Oxygen Sensor Heater Monitoring - 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 influences emissions. The monitoring function measures both, sensor heater current (voltage drop over a shunt) and the heater voltage (heater supply voltage) to calculate sensor heater resistance. The monitoring function is activated once per trip, once the heater has been switched on for a certain time period and the current has stabilized. For flow chart of monitoring function of oxygen sensor heating (Scheme 66)
4. Flow Chart Of Oxygen Sensor Heater Monitoring Function - (Scheme 65)
5. Oxygen Sensor Circuit Monitoring - Monitoring of electrical faults of sensors upstream and downstream of catalyst, consists of following: Unplausible Voltages - ADC voltages exceeding the maximum threshold VMAX are caused by a short circuit to battery voltage, or ADC voltages falling below the minimum threshold VMIN are caused by a short circuit of sensor signal or sensor ground to ECM ground. Unplausible Course Of Sensor Voltage - An open circuit of the sensor upstream catalyst can be detected, if the ADC voltage remains in a specified range after the sensor has been heated.

Scheme 70

See also:
• TESTS W/O CODES
• ELECTRICAL COMPONENT LOCATIONS - Z3
• 1997 MODEL COVERAGE
• TEST GROUP IDENTIFICATION
• VBM1.9VJGFEK & VBM1.9VJGKFK
• VBM2.8VJGKFK
• VBM4.4VJGFEK
• VBM1.9VJGFEK & VBM1.9VJGKFK
• VBM1.9VJGFEK
• VBM1.9VJGKFK
• VBM2.8VJGKFK
• VBM2.8VJGKEK
• VBM4.4VJGFEK