Diagnosis
DIAGNOSIS - IHKR E34 & IHKR E36
In addition to the diagnostic aids available for the IHKS, additional help is available to aid with IHKR diagnosis.
ETM DIAGNOSTIC PROCEDURES MANUALS
The Diagnostic Procedures manuals provide IHKR system information including general information on how the system works, lists of defect codes, and troubleshooting information for each code
DIAGNOSIS & INFORMATION SYSTEM
When the DIS is connected to a vehicle, it surveys the vehicle's electrical system, identifying which systems are present. It also determines which version of each system is present.
When the DIS has this information it knows which set of stored data it should use during system diagnosis and which features are available for that version of the system.
If Read Fault Memory is selected, the DIS displays any fault codes set in the control module. Fault memory should always be checked when beginning diagnosis, as a stored fault code may lead you directly to the problem cause.
GENERAL DIAGNOSIS TIPS
SYSTEM VOLTAGE
Don't neglect to check vehicle system voltage, since low or high voltage can drastically affect operation of the IHKR system. In general, the system may operate erratically.
Also, the control module modifies its stepper motor operation strategy during high or low vehicle system voltage conditions:
- Voltage below 9V - stepper motors are not operated
- Voltage from 9V to 11V - stepper motors operated with half frequency
- Voltage from 11V to 15.5V - stepper motors operated normally
- Voltage above 15.V - stepper motors are not operated
Y-FACTOR
If the IHKR system won't maintain the desired cabin temperature, use the DIS Status Request function to display the Y-factor. The Y-factor is a means of communicating how much heating or cooling the control module thinks is necessary to achieve the desired passenger compartment temperature. Values range from -27.5% (typically) to 100%. The higher the value, the harder the system is working to provide heat. The lower the value, the harder the system is working to cool.
Determine whether the Y-factor is reasonable for the knob settings and temperature conditions. For instance, if the vehicle has been parked outside overnight during cold weather, the Y-factor should be high (100%) when the IHKR system is turned on (so long as the desired temperatures are set at 68 °F or above).
Conversely, if the vehicle is parked in the sun on a hot summer day and maximum cooling is requested (left desired temperature knob rotated all the way counter-clockwise), the Y-factor should be at its minimum value (- 27.5%). If the Y-factor isn't at the expected value, something is clearly wrong
Is the control module getting bad data or is the module itself faulty? To determine the answer, use the DIS Status Request function to check left and right desired temperature values, the ambient temperature value, and the interior temperature value. Are they reasonable? Are there any faults present?
What temperatures are indicated for the heater core temperatures? In general, low Y-factors mean that cooling is desired, so the heater core temperatures should be low when cabin cooling is requested. Conversely, high Y-factors mean that heating is desired, so the heater core temperatures should be high.
Each of the temperature sensor values may be a clue to the cause of the problem.
WATER VALVES
If insufficient cooling is the complaint, remember that the default position for the water valves is fully open. If temperature sensor values look okay, except for one of the heater cores, make sure that the water valve is receiving the "close" voltage signal from the control module. If it is, determine that the valves are actually closing.
With the system operating and the DIS connected, view the water valve "on time" to make sure that the control module is pulsing the valves (neither maximum heating nor maximum cooling can be selected). Then, use a stethoscope to monitor the water valve housing. If the solenoid portion of the valve is functioning properly, you will hear distinct clicking sounds as the module pulses the solenoids.
INTERIOR TEMPERATURE SENSOR
If the system will not maintain the desired passenger compartment temperature, check the interior temperature sensor inlet grille in the control panel. The grille can become obstructed with dust and dirt, especially in a "smoking" car, and the sensor will not provide an accurate interior temperature reading.
Clean the grille using a vacuum cleaner, or carefully blow it clean using regulated shop compressed air.
Also, make sure that the sensor's fan is working. Hold a strip of paper near the sensor inlet grille and check that the paper is pulled against the grille. If the paper isn't pulled against the grille, remove the control panel and check for an obstructed passage or stalled fan motor.
COMPRESSOR/REFRIGERATION CYCLE
The refrigeration circuit can also be the source of insufficient cooling complaints. Check high-side and low-side pressures when the compressor is operating. Are they too low? Look for wet spots on the hoses or at fitting connections, evidence that oil (and refrigerant) is escaping.
Use the DIS to check evaporator temperature. When the compressor is operating, evaporator temperature should be from 34 °F to 37 °F.
Also, make sure that the [1][2]auxiliary fan is operating when the compressor is on. If it isn't, too little refrigerant will condense and the evaporator will be "starved".
BASIC TROUBLESHOOTING
- Always personally verify the customer complaint.
- Always verify that the complaint is truly a system malfunction.
- Perform a Quick Test to determine if the vehicle Systems have logged fault codes.
- Call up the faulted system or appropriate test schedule to verify the correct control module is installed in the car.
- Follow the Diagnostic Information System (DIS) on screen instructions and perform all tests as specified.
- Use the DIS and fault symptom diagnostic procedures as trained.
- Follow the appropriate test module procedures for systems that malfunction but fail to set faults in memory.