SL 600 (129.076) V12-6.0L (120.981) (1995)
management system is detected. The operator should bring the vehicle to the repair shop as soon as possible.
The malfunction memory can be accessed via the diagnostic connector (X11/4). The malfunction memory is not erased when disconnecting the
battery.
Air Injection Control (AIS)
In order for the catalytic converter to reach operating temperature as soon as possible, air from an air pump (125) is injected into the exhaust gas directly
behind the exhaust valves. The electronic clutch of the air injection is engaged by the LH control unit (N3/3) via the air injection relay (K17). At the
same time, the air injection pump switch-over valve is energized which applies vacuum to the air injection shut-off valve (126).
Air injection occurs after starting the engine at a coolant temperature between 10 °C (50 °F) and 44 °C (111 °F), an engine speed of less than 2750 RPM
and below a specified air mass. The air is injected for a maximum of 155 seconds depending on coolant temperature. The oxygen sensor control in
inactive during air injection.
Camshaft Timing Control
To improve the torque characteristics of the engine, the intake camshafts are "advanced" depending on engine speed and load.
The LH control units operate the camshaft timing adjuster solenoids (one per camshaft). When the solenoids (Y49/1 and Y49/2) are energized, the
camshafts advance. In "P" or "N" the adjustment is dependent on engine RPM only.
Engine speed:
Adjustment:
Up to 2000 RPM
Retarded
From 2000 - 4400 RPM
Advanced
From 4400 RPM
Retarded
Above 250 km/h (155 mph)
Advanced
Selector in "P" or "N"
up to 2500 RPM
Retarded
Selector in "P" or "N"
from 2500 RPM
Advanced
Charcoal Canister Purging Control (EVAP)
The fuel vapors stored in the charcoal canister are purged at temperatures above 70 °C (158 °F) via the purge switch-over valves (Y58/2 and Y58/3).
The vapors then get burned in the combustion process. In order to control the purge quantity, the LH control units activate the switch-over valves at a
frequency of 7.5 Hz (cycles). The purge quantity is determined by the duration of each cycle.
Exhaust Gas Recirculation Control (EGR)
The EGR valves are controlled by the LH control units via the EGR switch-over valves (Y27/2 and Y27/3). This switch-over valve is activated at coolant
temperatures above 65 °C (149 °F) and only if the engine is between the idle and full load condition.
Transmission 2>3 Upshift Delay Control
To heat up the catalytic converter faster, the no/partial load upshifts from 2nd to 3rd gear upshift in the automatic transmission is delayed. If the engine
coolant temperature is between 0 °C (32 °F) and 50 °C (122 °F), the LH control unit (N3/3) will delay the upshift to a maximum of 15 seconds after
engine start-up. The upshift occurs at higher RPM, accelerating catalytic converter warm-up.
The delayed transmission upshift is controlled via the switch-over valve (Y3/3). Vacuum is applied to the control pressure cable vacuum element via the
switch-over valve.