Air Conditioning (A/C) System Component Monitoring

12 AIR CONDITIONING (A/C) SYSTEM COMPONENT MONITORING

12.1 General Description
The engine control module recognizes the air conditioning status (on or off) as a torque request and compensates the engine torque demand accordingly.
The status of the air conditioning system does not result in use of a different strategy regarding ignition or fuel injection.
The components of the air conditioning system are not used for OBD functions and can not disable monitors. This applies to both separate and integrated climatic control modules. Integrated climatic control modules may be a separated part of the ECM as "box in a box" unit.

12.2 Monitoring Concept
The air conditioning system is not monitored by the OBD II system for the following reasons:
- Sensors of the air conditioning system are not used within OBD as an input signal.
- Actuators of the air conditioning system are not used as an OBD output component.
- Air conditioning system components can not disable any of the OBD monitors.
- Any failure mode of the air conditioning system does not cause exhaust emissions to exceed 1.5 times the applicable standard.
- Possible failures of the air conditioning system may result in reduction or loss of cooling efficiency during SC03. In this case the vehicle runs with lower load and the emission would not increase.

Determination of the influence on exhaust emissions of the air conditioning (AC) under the condition of following failure modes:
1. AC switched/commanded on --> AC compressor mechanically disabled
Result:
The FTP 75 / SC03 results are within normal variation on all concepts.
Therefore there is no other strategy used than the mentioned torque compensation.

2. AC switched/commanded off --> AC compressor running always
Result:
The FTP 75 results are higher than the comparable results from a FTP 75 conducted according legal requirements caused by additional load. The FTP 75 results do not exceeded the applicable standard. Therefore the failure modes of the AC do not exceed the criteria of "1.5 times of any applicable standard.