BMW Diagnostic System - IHKA (Automatic Climate Control system)

Diagnostic System Notes
The component functions and signals listed below are processed or controlled by the IHKA control unit, however, they are not stored as a defect code in the event of a defect:
- Speed signal output from the instrument cluster
- * All keys in the operating unit, switches for rear area flaps, independent heating and independent ventilation of the relay box, diode for right-hand drive coding in the operating unit
- Signal from terminal 30 h of the starter solenoid switch
- Voltage supply of function LEDs
- Control of function light for the rear window defogger in the rear window defogger button
- * Blower control voltage to blower motor output stage
- Diagnostic links RxD/TxD to BMW Service Tester

* These component functions and signals can be read out in the status list of the BMW DIAGNOSTIC SYSTEM.

When the IHKA operating unit is coded with a diode as right-hand drive, the texts "driver's side"/"passenger's side" are used by the BMW diagnostic system corresponding to the function of the control unit.

The IHKA control unit clears the defect code memory when the voltage supply (terminal 30, terminal 15) is interrupted or the ignition was switched off for longer than 3 minutes. The defective components or functions are stored as defect codes after the ignition is switched on.

The current defect code memory indicates whether a defect currently exists. The display "current defect" shows that the defect currently exists. The component or the function is then not used by the control unit. For instance, a relay is no longer activated by the control unit. If a "defect current" applies to the temperature sensors or control wheels, a substitute value provided by the control unit is used for these components. The substitute value is replaced by the current value when the defect no longer applies. "No defect" is then indicated under "current memory" on the corresponding defect page. The control unit makes an exception as regards defect code detection and storage in the case of the stepper motors. Here, a defect is only detected after ignition "ON", under the condition that the ignition was switched off for longer than 3 minutes beforehand or the voltage supply was interrupted. If a stepper motor defect occurs when the IHKA is in operation (ignition "ON") this is not stored in the form of a defect code.

NOTE: The windscreen heating relay status is derived from diagnosis of the outside temperature. A defect code is not detected.

Abbreviations
IHKA Automatic climate control
A Output
E Input
Max Maximum
AUTO Automatic
(control in accordance with the flap programs stored in the control unit)
Poti Potentiometer
M Ground