Starting, Function - GF07.10-P-1001MNL
Engine 176.9, 177.9 in model 217
Engine 176.9, 177.9 in model 222
Engine 177.9 in model 290
up to model year 2021
Starting function requirements, general points
- Circuit 87M (Engine management ON)
- Engine OFF
- Drive authorization system 4 (DAS 4) start enable
- Engaged gear range "P" or "N" or foot brake actuated (for A/T)
Starting, general points
For starting, the ME-SFI [ME] control unit (N3/10) reads in the following signals:
- Left and right intake camshaft Hall sensors (B6/4, B6/5), intake camshaft positions for ignition circuit detection
- Left and right exhaust camshaft Hall sensors (B6/6, B6/7), exhaust camshaft positions for ignition circuit detection
- Coolant temperature sensor (B11/4), coolant temperature
- Crankshaft Hall sensor (B70), engine speed
- Electronic ignition lock control unit (N73), "Circuit 50 signal" via chassis FlexRay (Flex E), powertrain control unit (N127) and drive train CAN (CAN C1)
The ME-SFI [ME] control unit actuates the following assembly parts to start the engine:
- Starter (M1)
- Ignition coils of cylinder 1+2 to cylinder 7+8 (T4 to T4/3)
- Fuel injectors for cylinders 1 to 8 (Y76/1 to Y76/8)
- The fuel system control unit (N118) and thereby the fuel pump (M3) directly and over the drive train CAN
The ME-SFI [ME] control unit coordinates the injection and firing order during starting based on the signals from the crankshaft Hall sensor and the camshaft Hall sensors.
The starter control in the ME-SFI [ME] control unit takes on actuation and cutout of the starter.
Function sequence for start
The starter control is subdivided into the following points:
- Function sequence for start begin
- Function sequence for start end
Function sequence for start begin
Through actuation of the KEYLESS-GO start/top button (S2/3) (with code 889 (KEYLESS-GO)), the ME control unit receives the "circuit 50 signal" from the electronic ignition lock control unit via drive CAN, powertrain control unit, and suspension FlexRay.
The ME-SFI [ME] control unit uses a ground signal to actuate the starter circuit 50 relay (K40/8 kH) on both sides. The power contact on the starter relay closes and the starter solenoid switch is supplied at "circuit 50" with voltage from "circuit 30".
Function sequence for start end
Starter control is carried out automatically by the ME-SFI [ME] control unit (touch start). This means that once the start process is initiated, switching off "circuit 50" will have no further influence on the start procedure.
When the engine cranking speed has reached approx. 400 to 700 rpm or a start time of approx. 5 to 40 s (depending on the coolant temperature), the ME-SFI control unit interrupts negative activation to the circuit 50 starter relay thereby ending the start procedure.
When actuating the ignition key the starting procedure can only be aborted by switching off the ignition.
During the starting procedure with the KEYLESS-GO start/stop button, the engine start can be aborted by tapping the button again.
A voltage dip limiter is installed at the positive battery terminal. Its task is to prevent a drop in the battery voltage below a defined voltage value during the starting procedure of the engine.
This is performed through temporary limitation of the starter current. Note here that a voltage of 12 V is present at the starter positive line only during the starting procedure.
| Electrical function schematic for starting | Engine 177.9 in model 290 up to model year 2021 | PE07.10-P-2701-97XBA | |
| Engine 176.9, 177.9 in model 217 Engine 176.9, 177.9 in model 222 | PE07.10-P-2701-97SEL | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNL |