Diagnostic Trouble Codes With Test Charts: Introduction

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES , proceed with self-diagnostics. BMW vehicles are equipped with 2 separate diagnostic connectors. OBD-II self-diagnostic system accesses Diagnostic Trouble Codes (DTCs) using a generic scan tool connected to vehicle Data Link Connector (DLC). See Fig 1, Fig 2 and Fig 3 . BMW self-diagnostic system accesses DTCs using special BMW hardware and software connected to round BMW engine diagnostic connector socket. See Fig 4 and Fig 5 .

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. 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.

Fig 1: Locating OBD-II Data Link Connector (Z3)

G98D11281

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 2: Locating OBD-II Data Link Connector (3 & 5-Series)

G98E11282

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 3: Locating OBD-II Data Link Connector (7-Series)

G98F11283

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 4: Locating BMW Engine Diagnostic Connector Socket (4-Cylinder Engine Shown; Others Are Similar)

G98G11284

Courtesy of BMW OF NORTH AMERICA, INC.

Fig 5: Locating BMW Engine Diagnostic Connector Socket (E46 Shown; Others Are Similar)

G99F05482

Courtesy of BMW OF NORTH AMERICA, INC.

BMW has a 20-pin diagnostic connector located in engine compartment in addition to a 16-pin OBD-II connector located inside vehicle . See Fig 4 and Fig 5 . The 16-pin OBD-II connector has been in all BMWs since 1996 to comply with OBD-II regulations requiring a standardized diagnostic port.

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.

1998 MODEL COVERAGE

Model	Engine	Fuel System
M Roadster	3.2L 6-Cyl. (S52)	Siemens (SFI)
M3	3.2L 6-Cyl. (S52)	Siemens (SFI)
Z3	1.9L 4-Cyl. (M44)	Bosch ML-Motronic (SFI)
Z3	2.5L 6-Cyl. (M52)	Siemens (SFI)
318i	1.9L 4-Cyl. (M44)	Bosch ML-Motronic
318ti	1.9L 4-Cyl. (M44)	Bosch ML-Motronic
323i	2.5L 6-Cyl. (M52)	Siemens (SFI)
323is	2.5L 6-Cyl. (M52)	Siemens (SFI)
328i	2.8L 6-Cyl. (M52)	Siemens (SFI)
328is	2.8L 6-Cyl. (M52)	Siemens (SFI)
528i	2.8L 6-Cyl. (M52)	Siemens (SFI)
540i	4.4L V8 (M62)	Bosch HFM-Motronic (SFI)
740i	4.4LV8 (M62)	Bosch HFM-Motronic (SFI)
740iL	4.4L V8 (M62)	Bosch HFM-Motronic (SFI)
750iL	5.4L V12 (M73)	Bosch HFM-Motronic (SFI-2 Control Units)