Electrical Systems - Other Auxiliary Equipment Faults and Problems

M73 Secondary Air Pump Circuit Rewiring

Model:
BMW E38_750iLA with M73 engine produced between August 1998 and October 1998
Complaint:
Due to the wiring for the secondary air circuit at the Engine Control Modules being reversed, the illumination of the check engine light may result causing the fault FC 79 (4F) – Undefined.
Remedy:
Utilize the ‘Service Menu’ of the Dealer Communication System, and based upon the response of the system either proceed with corrective action, or take no action at all.
If action is necessary the wiring in module connector number 4 of DME I pin 3 and DME II pin 31 must be swapped.

Reprogramming of Engine Control Module May Not Be Possible

Model:
BMW E38 – 740i/iLA with M62 engine and DSC 3 produced as of September 1998
BMW E38 _ 540i/iA/iTA with M62 engine and DSC 3 produced as of September 1998
BMW E39 _ 528i/iA/iTA with M52 engine and DSC 3 produced as of September 1998
Complaint:
Due to the DSC 3 control module troubling the communication path between the DIS/MODIC and the DME and/or EGS module, the reprogramming procedure is unable to perform and the following message is displayed: “Programming cannot be performed correctly! Test code 002400 Repeat programming if necessary.”
Remedy:
Before starting the programming operation the power supply to the DSC 3 module must be removed.

Vacuum Hose to Secondary Air Non-Return Valve

Model:
BMW E46 – 323i/iA, 328i/iA produced between April 1998 and July 1998
Complaint:
The vacuum hose going to the Secondary Air Non-Return Valve may be wrongly routed. Consequently if this hose connects with the exhaust system it may set off the following faults may set within the Engine Control Module (ECM/DME):

-Fault Code 245 (F5 hex) – Flow rate secondary air rate too slow bank 1
-Fault Code 245 (F6 hex) – Flow rate secondary air rate too slow bank 2

Remedy:
Utilize the ‘Service Menu’ of the Dealer Communication System, and based upon the response of the system either proceed with corrective action, or take no action at all.
If action is necessary then check the condition and routing of the vacuum hose going to the non-return valve on all affected vehicles if required reroute. If fault code 245 or 246 are set in the DME the vacuum hose going to the non-return valve will need to be replaced if it is damaged.

Motronic M1.1 – Circuit Suppression

Model:
BMW E32 (735i), BMW E30, BMW E24, Equipped with M1.1 Fuel injection- 1987 and 1988 Model Years (prior to 5.88 production)
Complaint:
M1.1 control unit durability can be affected by migrant voltage surges from the “Check Engine” light circuit.
Remedy:
The following Service Action is necessary: Install suppression diode harness (P/N 88 88 2 000 100)

Idle Mixture Check and Adjustment (after major engine repair)

Model:
BMW M3, BMW M5, BMW M6
Complaint:
M3, M5 and M6 cars that do not have CO-screws on the exhaust manifold pipes may need the idle mixture checked and adjusted after majoe engine repair.
Remedy:
Follow this procedure to ensure the idle mixture is correctly adjusted if necessary.

-Engine is at operating temperature; the oil needs to be at least 60 degrees C or 140 degrees F.
-The ignition timing and valve clearance are correct.
-The plate synchronization is correct
-The idle speed is correct.
-All electrical consumers and air conditioner must be switched off.
-Connect the digital mixture measurement unit (integrator voltage measuring unit for 318i-P/N 88 88 6 126 400) to engine diagnosis socket (BMW service tester cable is connected to digital mixture measurement unit).
-Start engine.
-Flashing of the red LED at regular intervals indicates normal operation of the oxygen sensor.
-Read integrator voltage on LCD display. If necessary, adjust to a value of 6 plus/minus 3 volts at the airflow meter bypass screen while the red LED pulsates at a regular interval.
-If the red LED stays “on” continuously, the engine idle speed mixture is too lean, or the oxygen sensor is defective.
-If the red LED stays “off” continuously, the engine idle speed mixture is too rich.
-Adjust the idle mixture by carefully turning the airflow meter bypass screw to a value of 6 plus/minus 3 volts, until the LED flashes at a regular interval.
-Check the engine idle speed and integrator voltage.

Idle Control Valve Binding – No Start

Model:
BMW E36 with M44 engine
Complaint:
Due to a binding idle control valve the engine may not start or will only start when the accelerator pedal is depressed making the throttle plate open. This is caused by the air gap between the rotary slide valve and the idle control valve housing being too small which causes the valve to bind in the closed position. When this happens the throttle plate by-pass air is restricted during cranking causing the engine not to start or very difficult to start.
Remedy:
A new style idle control valve part number 13 41 1 435 846 should be installed.

Whistling Noise from Idle Control Valve

Model:
BMW E36 with M44 engine
Complaint:
The idle control valve can emit a whistling noise when the engine is at idle. This is due to adverse tolerances between the idle control valve housing and the rotary slide valve.
Remedy:
A new style idle control valve part number 13 41 1 435 846 should be installed.

Relays

Model:
All BMW
Complaint:
If a relay sticks in the closed position after the ignition is turned off the following complaints could arise:

-The auxiliary fan continues running.
-A/C – heater blower motor continues running.
-Fog lights and/or headlights stay on.
-The battery goes dead overnight.
-The rear window defogger stays on.

This is due to the battery voltage still being present when the ignition is turned off. Apart from the auxiliary fan the components need their control switch left on for the situation to occur. The auxiliary fan will automatically continue running in this condition.
Remedy:
Replace the defective relay.

Vibration Resistant Battery

Model:
BMW E36 Convertible
Complaint:
Not only is the E36 convertible battery an energy source it is also a vibration damper. The battery also has a special battery tray with integrated vibration absorber.
Remedy:
If the battery needs to be replaced a vibration resistant one must be installed.