Scan Tool Testing and Procedures

NOTE: All troubleshooting should begin by "Checking the Basics". Certain basic faults can be undetectable by the self-diagnostic system of the DME control unit and in some cases can actually interfere with the self-checking and fault memory operation. Refer to "Checking the Basics".
Checking the Basics

Diagnostic Equipment:

In addition to the BMW Service Tester and the Mobile Diagnostic Computer (MoDiC), various manufacturers have produced diagnostic equipment compatible with BMW diagnostic systems. Although some differences exist between the range of capabilities, procedures and displays, these testers are capable of identifying BMW Diagnostic Trouble Codes (DTC), providing data stream information, and typically suggest some direction for remedy of the problem. Equipment recognized at the time of this publication include:

- KTS300 "HAMMER" by Robert Bosch

- 5510 BMW ENGINE DIAGNOSTIC TOOL by Assenmacher Special Tools (AST)

- CARSOFT BMW DIAGNOSTIC SOFTWARE by Krahe

NOTE: Since typical diagnostic testers usually have differences in diagnostic capabilities, application of the information presented in this section may vary. Always follow the directions provided by the equipment manufacturer.

Initialization of Diagnostic Procedure
Communication with the Digital Motor Electronic (DME) and other vehicle control units is established with the use of a Diagnostic Scan Tool.

Control Unit Identification
If necessary, the control unit can be quickly identified with the aid of these data (factory requirement). Automatic allocation of the diagnostic programs is also based on these control unit numbers.

Effective Range of the Self-Diagnosis Function
The self-diagnosis function is an aid to facilitate fast fault tracing in the vehicle's electronic systems. The BMW MoDiC or equivalent tester provides the necessary access for the user. Self-diagnosis of the control unit detects defects provided the necessary conditions for this have been fulfilled (time, temperature, load etc.). However, defects can only be registered when there is an electrical connection to the control unit. If this is not the case, the check must be performed using conventional methods (e.g. ignition voltage, fuel pressure, mechanical functions etc.).

Diagnostic Trouble Code Storage
Defect codes are stored after the engine has been started. If several defects are detected, they appear in the order they first occurred.

The operating conditions as stored apply only to the conditions, under which the defect was detected for the first time. An intact voltage supply (battery charged) is the prerequisite for maintaining the memory contents.

Substitute values may be active if no malfunctions can be found despite a defect code being stored. Troubleshooting should still, however, be carried out.

Defects which influence the fuel/air mixture are indicated by a lamp (check engine) in the instrument cluster. As a check, this lamp lights constantly during the period of time between "ignition ON" and engine start.

If the defect code memory has no defect code stored although there is a defect in the vehicle, either the test conditions (e.g. temperature, time, load etc.) for defect detection were not fulfilled or it was technically not possible to store a defect code.

Diagnostic Trouble Code Memory Interrogation
The first step should always be to monitor the defect code memory. If one or several defect codes are stored, it is advisable to record these data immediately. Since it is often necessary during the testing procedure to cut the power supply or to disconnect the connector from the control unit, the contents of the defect code memory will be unintentionally deleted as a consequence.

Diagnosis Without Diagnostic Analyzer
The "Check Engine" light is also used to display faults which are stored in the control unit's memory. When the self-diagnostic procedure is initiated, the DME control module pulses the number of the trouble code via the "Check Engine" light.

NOTE: Only malfunctions which would cause the vehicle to fail to comply with emission certification standards will be displayed via the "Check Engine" light. This flash-code system is not a substitute for the BMW Service Tester or equivalent equipment and a thorough troubleshooting procedure. It is only helpful as a quick and rough predetermination of some possible failure sources.

NOTE: Troubleshooting without a thorough understanding of DME system operation, may lead to misdiagnosis and needless expense. Always review Description and Operation.

The learned adaptation values are lost if the battery or the DME control unit is disconnected. This may result in difficulties in starting the engine or the engine may stall when idling. These problems are generally rectified after a short test drive.