Engine Controls - Theory & Operation: Diagnosis BMW Z3 E36 рестайлинг

BMW MODIC DIAGNOSTIC TESTER

The BMW Mobile Diagnostic Information Center (MoDiC) was developed to meet the diagnostic needs of BMW vehicles for the future. It compliments the Diagnostic Information System (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. You have the ability to take the tester anywhere in the workshop and to the vehicle. It can also 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

1. Interchangeable batteries.
2. UNIX operating system.
3. 3 Gigabyte hard drive for data/program storage.
4. 32 MB working memory.
5. 90 megahertz Pentium processor.
6. Diagnosis Information System (DIS).
7. Technical Information System (TIS).
8. Digital multimeter.
9. Counter.
10. Single channel oscilloscope.

BMW Diagnostic Concept

BMW diagnosis proceeds directly from the faults and their symptoms. Not only does this minimize time and effort but the quality of repair services can be significantly enhanced. Troubleshooting has become an integrated procedure covering all systems at once. The diagnosis program suggests a test schedule and determines the sequence of tests. These features allow faults to be located more easily and with greater precision. Diagnostic procedural steps are

1. Start of diagnosis.
2. Vehicle identification.
3. Brief test (mandatory).
4. Fault symptom selection.
5. DIS test schedule (inspection plan).
6. Processing of test modules (test information).
7. Examining results of diagnosis.

The number and sequence of test schedule items is calculated on the basis of seriousness of the symptom and number of times the symptom has been observed. Test results are continually analyzed, and the inspection plan is revised accordingly. Test results can be assigned one of the following status items

1. Test not performed.
2. Test performed, result okay. If the result of a test module is okay, the test modules subordinate to that module are not included in the test schedule.
3. X = not okay. If the result of a test module is not okay, the test modules subordinate to that module are included in the test schedule.
4. ? = Result not known/test interrupted.
5. > = Test is being carried (currently active). The results of tests already completed influence the order of preference set up for remaining test modules. Use continue arrow to proceed to next test. DIS/MoDiC highlights test which should be carried out next. The results of tests already completed are indicated to the left of the test designations. The test schedule is revised each time test schedule screen is reentered following the completion of a module. If a fault has been rectified or its symptoms have changed, this is indicated in the inspection plan display (sequence of test modules). Fault memory contents are assessed according to various criteria (e.g. frequency, temperature).

Start Of Diagnosis

Call up the diagnosis program and select the appropriate vehicle. The tester mode is now installed according to information stored in the equipment network so vehicle can be identified (E39, E46, etc.).

Fault Symptom Selection

Once the brief test has been completed, use the continue arrow (bottom right) to call up the fault symptom selection screen. The fault symptom selection screen displays all fault memories set for troubleshooting purposes. Service technicians can enter fault symptoms observed by themselves or by the vehicle owner. This is done by selecting the appropriate items in a predefined list of symptoms. Several fault symptoms can be selected simultaneously. Use the transfer key to transfer selected fault symptoms into the display The test schedule is generated on the basis of both the symptoms observed by customers or service technician and the contents of the fault memories.

Test Schedule

Test schedule is generated specifically for the problem at hand based on all current fault symptoms including those stored in fault memories of other control modules. Diagnosis tests are prioritized in an order established by the MoDiC/DIS. Test schedule screen displays one or several symptoms, diagnosis tests and corresponding test modules.

The number and sequence of test schedule items is calculated on the basis of seriousness of the symptom and number of times the symptom has been observed. Test results are continually analyzed, and the inspection plan is revised accordingly. Test results can be assigned one of the following status items (listed in on line help)

1. Test not performed, or test performed, result okay. If the result of a test module is okay, the test modules subordinate to that module are not included in the test schedule.
2. X = not OK If the result of a test module is not OK, the test modules subordinate to that module are included in the test schedule.
3. ? = result not known test interrupted?
4. = > = test is being carried (currently active). The results of tests already completed influence the order of preference set up for remaining test modules. Use the continue arrow to proceed to the next test. DIS/MoDiC highlights the test which should be carried out next (dark background). The results of tests already completed are indicated to the left of the test designations. Test schedule is revised each time TEST SCHEDULE screen is reentered following the completion of a module. If a fault has been rectified or its symptoms have changed, this is indicated in INSPECTION PLAN display (sequence of test modules). Fault memory contents are assessed according to various criteria (e.g. frequency, temperature).

Test Information

Press continue arrow to advance to the next test schedule. Test information screen appears automatically. The test information screen automatically displays documents including: wiring schematics, functional descriptions, connector locations, etc. Test dialog box displays test points and nominal values automatically. This screen format is used throughout the diagnostic software for all systems.

Expert Mode Troubleshooting

Expert mode troubleshooting can be activated at any time during system guided troubleshooting. To operate, press operating button in the navigation line to access documents, function and component selection, and test schedule screens. To return to system guided diagnosis, press appropriate button. Any documents assigned to the diagnosis test which is currently active may be viewed. A new diagnosis test can be selected at any time in FUNCTION AND COMPONENT SELECTION. Press TEST SCHEDULE button to call up the test modules assigned to diagnosis tests. A second schedule list, OWN TEST SCHEDULE now displays test modules assigned to selected diagnosis tests.

Basic Troubleshooting (BMW Diagnostic System)

Personally verify customer complaint. Verify that complaint is truly a system malfunction. Perform QUICK TEST to determine if vehicle systems have logged fault codes. Call up faulted system or appropriate test schedule to verify correct control module is installed in car. Follow Diagnostic Information System (DIS) on screen instructions and perform all tests as specified. Use DIS and fault symptom diagnostic procedures. Follow appropriate test module procedures for systems that malfunction but fail to set faults in memory.

LEAK DIAGNOSIS TEST PRECONDITIONS (X5)

The DME only initiates a leak diagnosis test every second time the criteria are met. The criteria is as follows

1. Engine off with ignition off.
2. Engine Control Module still in active state or what is known as "follow up mode" (main relay energized, control module and DME components online for extended period after key off).
3. Prior to engine/ignition switch off condition, vehicle must have been driven for a minimum of 20 minutes.
4. Prior to minimum 20 minute drive, the vehicle must have been off for a minimum of 5 hours.
5. Fuel tank capacity must be between 15 and 85 percent (safe approximation between 1/4 -3/4 of a tank).
6. Ambient air temperature between 20-95°F (-70-35°C).
7. Altitude less than 8,202 feet.
8. Battery voltage between 11.5 and 14.5 volts. When these criteria are satisfied every second time, the PCM will start the fuel system leak diagnosis test. Test will typically be carried out once a day.

DIAGNOSIS MODULE - TANK LEAKAGE (M5 & X5)

A Fuel System Leak Diagnosis Pump (LDP) is equipped on the M5 and X5. The pump will eventually replace the current vacuum LDP on all vehicles. The pump is manufactured by Bosch to BMW specifications. Bosch PCMs identify the electrical function of the pump as DM-TL. Siemens PCMs identify the electrical function of the pump as LDP-M1. The pump is located in the driver's side rear wheel well. (Scheme 2)

Scheme 2

LEAKAGE DIAGNOSIS PUMP (LDP)

LDP system is capable of detecting a leak as small as.019" (0.5 mm). LDP is a unitized component that contains vacuum chamber, pneumatic pump chamber, DME activated vacuum solenoid, and reed switch providing a switched voltage feedback signal to DME. LDP assembly is only replaceable as a complete unitized component, however, it is separate from charcoal canister.

During every engine cold start, LDP solenoid is energized by the PCM. Engine manifold vacuum enters upper chamber of LDP to lift up spring loaded diaphragm pulling ambient air through the filter and into the lower chamber of the LDP through one way valve. Solenoid is then de-energized, spring pressure closes the vacuum port blocking the engine vacuum and simultaneously opens the vent port to balance tube which releases captive vacuum in upper chamber. This allows compressed spring to push the diaphragm down, starting limited down stroke. (Scheme 3)

The air that was drawn into the lower chamber of the LDP during the upstroke is forced out of the lower chamber and into the evaporative system. Electrically controlled repetitive up/down stroke is cycled repeatedly building up a total pressure of approximately +25mb in the evaporative system. After sufficient pressure has built up (LDP and its cycling is calibrated to the vehicle), leak diagnosis begins and lasts about 100 seconds. Upper chamber contains an integrated reed switch that produces a switched high-low voltage signal that is monitored by the PCM. Switch is opened by magnetic interruption of the metal rod connected to the diaphragm when diaphragm is in top dead center position. Repetitive up/down stroke is confirmation to the PCM that valve is functioning.

PCM also monitors the length of time it takes for the reed switch to open, which is opposed by pressure under the diaphragm in the lower chamber. The LDP is still cycled, but at a frequency that depends upon the rate of pressure loss in the lower chamber. If pumping frequency is below parameters, there is no leak present. If pumping frequency is above parameters, this indicates sufficient pressure can not build up in lower chamber and evaporative system, indicating a leak. A fault code can be recorded by each PCM indicating an evaporative system leak. After test completion, PCM releases ground path to LDP and internal spring pushes diaphragm for full down stroke. At bottom dead center, diaphragm rod opens canister vent valve. This allows for fresh air intake from filter for normal purge system operation. The LDP is diagnosable with DIS including a service function activation test.

Scheme 3

SELF-DIAGNOSTIC FEATURE

PCM has a self-diagnostic feature which detects malfunctions in emission-related components and stores Diagnostic Trouble Codes (DTCs). PCM provides a substitute value if a failure occurs in 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. To aid in trouble shooting, stored fault codes and sensor values can be monitored via PCM and actuated components.

Vehicles are equipped with an OBD-II self-diagnostic system which can utilize a generic scan tool connected to in-vehicle Data Link Connector (DLC). In addition, vehicles are also equipped with a BMW self-diagnostic system which accesses DTCs using special BMW hardware and software connected to underhood BMW engine diagnostic connector socket. See SELF-DIAGNOSTICS article.