Description of On-Board Diagnostic System - Automatic Climate Control (IHKA)

Notes on the BMW DIAGNOSTIC SYSTEM:

The component functions and signals listed before 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 EKM
- * All keys in the operating panel, independent heating and independent ventilation of the relay box, diode for right-hand drive coding in the operating unit
- Signal from terminal 30h 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 the BMW SERVICE TESTER

Component functions and signals marked with * can be read out in the status list of the BMW SERVICE TESTER.

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 4 minutes.

The defective components or functions are stored as defect codes after the ignition is switched on.

The display "defect current" 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.

The control unit makes an exception as regards defect code detection and storage in the case of the stepping motors.

Here, a defect is only detected after ignition "ON", under the condition that the ignition was switched off for longer than 4 minutes beforehand or the voltage supply was interrupted.

If a stepping motor defect occurs when the IHKA is in operation (ignition "ON"), this defect is not stored in the form of a defect code.

Troubleshooting:

Notes:

- Troubleshooting with BMW DIAGNOSE SYSTEM
- Battery charged, U-min> 12 V
- Fuses associated with the IHKA are okay
- The suitable adapter must be used for testing and the IHKA must be connected such that it is fully operable. The control unit stores defect codes when disconnecting components and during testing. The defect codes stored prior to testing must therefore be printed out.
- The inputs and outputs listed in the following are not stored in the defect code memory of the IHKA control unit:
- Inputs (E): Buttons (matrix circuit), terminal 50, terminal 15, terminal 30, vehicle speed signal, diagnostic link RxD
- Outputs (A): LEDs for function lights, blower control voltage, buttons (matrix circuit), diagnostic link TXD

A short to ground or a break is detected at the relay outputs when the relay is not driven. A short to plus can only be detected when the relay is activated.

Table of substitute values:

Defective components Substitute value

Left heater sensor 55 °C
Right heater sensor 55 °C
Outside sensor 0 °C
Evaporator sensor - 5 °C
Interior sensor 24 °C

Table of substitute values:

Defective components Substitute value

Left temperature control wheel 24 °C
Right temperature control wheel 24 °C
Air flow control wheel 50 %
Mixing air control wheel 50 %