Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Start procedure, function - GF07.15-P-2001MCU
ENGINES 132.9 in MODEL 451.3 /4
The start process includes the following partial functions:
- Circuit 15 On
- START
- Start quantity control
- Post-start enrichment
Circuit 15 ON
- The SAM control unit checks drive authorization and applies an appropriate signal to the CAN.
- The ME-SFI [ME] control unit requests the CHECK ENGINE indicator lamp in the instrument cluster to light up shortly.
- The fuel pump with fuel level sensor is actuated via the SAM control unit for about 25 seconds.
This approach is particularly required after long periods of being switched off. This ensures that the fuel injection valves are supplied with sufficient fuel during starting. An engine start must be completed, however, before repeated actuation of the fuel pump with fuel level sensor.
Starting
The start function is activated by turning the transmitter key from position 1 (circuit 15 On) to position 2 (circuit 50 On) in the ignition/ starter switch.
Actuation of the starter takes place directly by the SAM control unit.
The start process is ended again as soon as terminal 50 is no longer applied at the SAM control unit or the engine cranking speed is reached.
Start quantity control
As soon as the first rpm signal is recognized by the crankshaft position sensor during the start process, the SAM control unit energizes the fuel pump with fuel level sensor permanently. In order to facilitate starting of a cold engine, fuel is also injected during the starting procedure. The increase in injection quantity (start quantity) takes place depending on the coolant temperature and is achieved through extending the injection time.
The start quantity control is enabled after starter recognition and remains active until a stable idle speed is recognized by the ME-SFI [ME] control unit.
The higher the coolant temperature, the lower is the start quantity enable by the ME-SFI [ME] control unit.
Post-start enrichment
When the engine is cold, fuel precipitates on the walls of the intake manifold and is not available to the engine for combustion. The missing fuel volume is compensated by the post-start enrichment function.
After the cold start the fuel-air mixture is enriched for short time through longer injection times of the fuel injection valves.
Post-start enrichment is achieved by the ME-SFI [ME] control unit and is dependent on the coolant temperature at engine start.
| Instrument cluster, component description | A1 | GF54.30-P-6000MCU |
| Coolant temperature sensor, component description | B11/4 | GF07.04-P-6040MCC |
| Component description for the intake manifold pressure sensor | B28 | GF07.04-P-6062MCC |
| Crankshaft position sensor, component description | L5 | GF07.04-P-6010MCC |
| Component description for fuel pump | M3/3 | GF47.20-P-2000MCC |
| ME-SFI [ME] control unit, component description | N3/10 | GF07.61-P-6000MCU |
| SAM control unit, component description | N10/10 | GF54.21-P-4157MCU |
| Ignition coils, component description | T1/1, T1/2, T1/3 | GF15.10-P-2100MCC |
| Fuel injection valves, component description | Y62/1, Y62/2, Y62/3 | GF07.03-P-6010MCC |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.