Notes on HHT diagnosis
Only the CAN version of the "radio frequency locking system with integrated immobilizer" (RFL) has diagnosis capability. This means that diagnosis using the HHT is only possible in vehicles with engine 601.
PWM version (vehicles with engine 111)
Diagnosis using the HHT is not possible. However, it is possible to read out the status of the immobilizer (activated/deactivated) using the HHT by reading the PEC engine control module actual values.
CAN version (vehicles with engine 601)
Diagnosis takes place via the CAN bus. The DAS engine control module transfers data between the radio frequency locking system control module and the HHT, which is connected to the 38-pin diagnosis connector.
The DAS and RFL control modules that are installed in the vehicle are bound to each other by an "identification". For this reason, a faulty function in one of the systems may affect both control modules. Therefore both systems have to be taken into consideration for troubleshooting.
Not all control module functions are active in diagnosis mode. For example, it is not possible to unlock or lock the vehicle using the radio frequency locking system (transmitter key).
The immobilizer monitoring lamp on the instrument cluster may illuminate during or after performing diagnosis. This can be reset by activating and deactivating the immobilizer in the usual way using the transmitter key.