The emissions warning lamp in the Driver Information Module (DIM) has a warning symbol. This warning symbol varies depending on the market. The
warning symbols are:
"Engine symbol" (not USA)
"CHECK ENGINE" (MIL - Malfunction Indicator Lamp, USA only).
The warning lamp lights when the ignition key is turned to position II. The warning lamp will go out after approximately 15 seconds or if the engine is
started when no fault is found in the engine management system.
If Readiness is not complete (certain diagnostic functions not completed), the warning lamp will flash instead of going out when the ignition key is in
The warning lamp will light if there is a fault in one of the parameters in the engine management system. The warning lamp will also light in response to
a request transmitted via the control area network (CAN) if there is a fault in the transmission control module (TCM) which affects emissions.
Electronic throttle unit
The electronic throttle unit, using the PWM control signal from the engine control module (ECM), regulates the amount of air for engine combustion.
This is done using an electronically controlled shutter.
The aluminium electronic throttle unit consists of a round throttle disc on a spindle. The spindle is driven by a DC motor (damper motor), gear wheel and
two springs; one for opening and one for return.
By changing the polarity of the power supply, the DC motor can be run in both directions. At one of the limit positions the throttle disc is closed so that
minimal air can pass the throttle unit. In the other limit position, the throttle disc is parallel to the air flow. This provides maximum airflow through the
electronic throttle unit.
Two permanent magnets in the gear sector on the throttle spindle are used to check the position of the throttle disc. The permanent magnets affect two
throttle position (TP) Hall sensors in the cover. The analog signals from the two sensors are transmitted to the engine control module (ECM). The signals
are offset. The engine control module (ECM) compares these signals with the stored desired values to check if they are plausible.
The electronic throttle unit is located on the engine intake manifold. In the event of a fault, the throttle unit must be replaced as a single unit.
The engine control module (ECM) can diagnose the electronic throttle unit.
Throttle position (TP) sensor
See Design, Electronic throttle unit.