Electronic Transmission - Overview: Diagnosis BMW Z3 E36 рестайлинг

TROUBLESHOOTING THE CAN BUS

The failure of communication on the CAN bus can be caused by several sources

1. Failure of the CAN bus cables.
2. Failure of one of the control units attached to the CAN.
3. Failure of the voltage supply or ground to individual modules.
4. Interference in the CAN bus cables.

DIAGNOSIS & TROUBLESHOOTING

Due to the cost and complexity of today's electronic transmissions, BMW recommends that the following procedures followed before any repairs are performed. It is important that the technician perform some basic diagnostic procedures

1. Always verify customer complaint, make sure the complaint is not related to normal operation. (i.e. Warm Up Phase, AGS operation etc.).
2. Survey Fault Memory - Perform complete quick test. There may be other systems that interface with EGS that could cause faults. (i.e DME, ASC/DSC, IKE/Kombi etc.).
3. Print out all fault codes with fault conditions. Also print out copy of Identification page and diagnostic report.
4. Check to see if there are any service bulletins that apply to your specific complaint.
5. Ensure that battery voltage is sufficient. Battery voltage must be greater than 12.5 with ignition switched off. Check battery connections for tightness and condition.
6. Check ground connections. (chassis to engine, grounds to bulkhead and shock tower).
7. Check over vehicle to look for transmission leaks, physical damage, loose connections etc.
8. If necessary, check fluid level and condition using DISplus or GT-1.
9. Check to see if any aftermarket or performance components have been installed that could effect transmission operation. (DME or EGS software as well as any engine modifications).
10. Check repair history to see if there were any recent repairs that could effect the proper operation of the transmission (i.e. engine replacement with damaged dowel pin etc.).

ESTABLISHING A DIAGNOSTIC PLAN

Once all of the pre-diagnostic criteria has been satisfied, a logical diagnostic plan should be followed. A logical, well organized diagnostic plan will help avoid improper diagnosis, unnecessary parts replacement and lost diagnostic time. The productivity of the technician can also be improved by following a logical, common-sense approach to problem solving. The following steps are recommended to form a diagnostic plan

1. Verify the Customer Complaint - This step is the most important, but also the most overlooked. The focus should always be on the exact customer concern. Make sure that the customer complaint is not a misunderstanding of proper vehicle operation. This step can avoid unnecessary diagnosis and lost time. Also make sure that the conditions under which the concern has occurred are duplicated. For example: If the customer is complaining about a shifting concern after a cold start, then the vehicle should be road tested under those conditions.
2. Analyze the Problem - Once the complaint has been verified, then all available resources should be used to find the "root cause" of the complaint. Start out by checking technical service bulletins. Use the DISplus or GT-1 to access the diagnostic program and perform Diagnostic Test Modules where applicable. Wiring diagrams should also be used when needed.
3. Isolate the Problem - Now, the problem can be narrowed down into the final steps of diagnosis. Using proper tools and procedures, the technician can "Isolate" by using the process of elimination and common sense. Perform all necessary electrical checks such as Voltage Drop, resistance measurements etc.
4. Repair the Problem - Once the concern has been correctly identified, perform all necessary repairs.
5. Verify the Repair - Make sure the customer concern has been rectified. Road test the vehicle under the same conditions whenever possible.

DIAGNOSIS PROGRAM

There are two diagnostic formats (programs) used on current model BMW vehicles. The earlier diagnostic program was used on the E38 and E39. The latter diagnostic program was introduced as the "E46 Diagnostic Concept". This is used on the E46, E65 and the E52 (Z8). The E53 X5 uses a mixture of both diagnostic programs depending upon engine/transmission options. Below is an example of the earlier diagnostic program.

The diagnostic program contains the following features

1. Fault Symptoms - This is a symptom driven program that will lead the technician into guided diagnostics. It contains several possible fault scenarios that are common to electronic transmissions. This path is helpful when the technician is not sure where to start in his diagnostic plan.
2. Function Test - There are no function tests for electronic transmissions.
3. Service Functions - This is where you will find the ATF level check function. Also Test Codes can be obtained and printed out for warranty purposes. The Adaptation values can be cleared as well as printed out.
4. Expert Mode - Expert Mode should be used when the technician has a thorough working knowledge of the system. You will find several items in expert mode: Read/Clear fault memory, Diagnosis (Status) requests, Component Activation and Test Modules.

TEST MODULES

Test modules are found in the diagnosis program of the DISplus and GT-1. These allow the technician to take advantage of a guided diagnostic plan. The program will direct the technician through the various steps using a "trouble tree" format. When using test modules it is important to follow the instructions exactly. Due to the complex nature of some faults, the test modules are not always conclusive. The test module is only as effective as the information provided by the technician. The technician also needs to rely on his experience and some common sense. The test modules should be used to assist the technician, not as a replacement for good diagnostic skills.

DIAGNOSTIC TIPS

The following consists of some helpful hints to assist the BMW diagnostic technician. It is designed to assist the technician to form a logical path of diagnosis. These suggestions should be used in conjunction with other approved diagnostic routines. Transmission concerns can be broken down into several categories

1. Shift Quality Complaints - Shift Quality complaints consist of harsh up or down shifts, improper shift points and erratic shifting. These complaints could be related to electronic/software issues or hydraulic/mechanical problems. Perform quick test and check TSB's before proceeding. As with most concerns, check the transmission fluid level and condition as well.
2. Delayed/No Upshifts - Before proceeding on delayed upshift complaints, make sure you are aware of the conditions that this occurs. This could be normal operation, such as the "Warm-up Phase" program. Always check front tires for proper inflation pressures, correct size and type. Also check for uneven tire wear. Variations in front tire size from left to right can activate the AGS "Curve Recognition" feature. The TCM will interpret the difference in wheel speed signals as being a turn and suppress (or delay) upshifts.
3. Slipping - This type of issue is usually associated with a fault code. Be sure to check the transmission fluid level and condition.
4. Noise, Vibration - Noises and vibrations should be checked over by a good visual inspection. Look for loose transmission or engine mounts. Check the driveshaft, center bearing and flexible coupling (or constant velocity joints). Also check the lateral alignment of the driveshaft.
5. No Forward or Reverse Gear - Start by checking transmission fluid level and note the fluid condition. Inspect for leaks and external transmission damage.
6. Leaks - When investigating transmission leaks, be sure to verify that the suspected leak is actually transmission fluid. Engine oil, hydraulic and brake fluid can be mistaken for a transmission leak. Check the transmission cooler lines, transmission cooler and transmission pan gasket. Try to locate the source of the leak.
7. Fault Codes - Perform COMPLETE short test (Quick test) on all vehicle systems. It is important to survey all systems in the event that a related system is causing the transmission fault. Always print out the ID Page, Fault codes and fault conditions.