A ver voy a intentar añadir algo de info que creo que alguna cosa estamos diciendo mal.

Según dices tu astra es 1.6 100CV... eso significa que puede ser el C16SE (8v) o el X16XEL (16v). En cualquier caso, los 2 tienen multec como centralita.

He buscado la lista de fallos:

Código:
 	GM-Multec Code Chart:

Code: 	Item: 	Fault:

12 	Initiation of diagnosis. 	n/a
13 	Oxygen sensor 	No change in voltage/open circuit.
14 	Coolant Temperature Sensor (CTS) 	Low voltage
15 	Coolant Temperature Sensor (CTS) 	High voltage
16 	Knock signal circuit 	n/a
18 	Knock control processor 	n/a
19 	Crank Angle Sensor (CAS) 	Incorrect RPM signal
21 	Throttle Potentiometer Sensor (TPS) 	High voltage
22 	Throttle Potentiometer Sensor (TPS) 	Low voltage
24 	Vehicle Speed Sensor (VSS) 	No speed signal or low voltage
25 	Injector valve 	Low voltage
28 	Fuel pump relay contacts 	Contact problem
29 	Fuel pump relay 	Low voltage
32 	Fuel pump relay 	High voltage
33 	Manifold Absolute Pressure (MAP) sensor 	High voltage
34 	Manifold Absolute Pressure (MAP) sensor 	Low voltage
35 	Idle stepper motor 	Poor or no idle speed control
41 	Amplifier control signal, cylinders 2 and 3 (Direct Ignition System (DIS)) 	High voltage
42 	Amplifier control signal, cylinders 1 and 4 (Direct Ignition System (DIS)) 	High voltage
43 	Primary ignition (distributor systems) 	High voltage
44 	Oxygen sensor 	Air/Fuel mixture too lean (weak)
45 	Oxygen sensor 	Air/Fuel mixture too rich
46 	Amplifier (Direct Ignition System (DIS)) control signal (A+B) 	High voltage
47 	Linear exhaust gas re-circulation (EGR) position 	n/a
49 	Battery supply to Engine Control Unit (ECU) 	High voltage (greater than 17 volts)
51 	Engine Control Unit (ECU) 	Defective ECU (disconnect and reconnect (ECU), then recheck for fault codes). Memory failure
52 	Secondary air pump relay 	Low voltage
53 	Secondary air pump relay 	High voltage
54 	Idle Carbon Monoxide (CO) potentiometer 	n/a
55 	Engine Control Unit (ECU) fault 	Renew Engine Control Unit (ECU)
56 	Air control soleniod 	Low voltage
57 	Air control soleniod 	High voltage
61 	Fuel tank vent valve (FTVV) 	Low voltage
62 	Fuel tank vent valve (FTVV) 	High voltage
63 	Amplifier control signal, cylinders 2 and 3 (Direct Ignition System (DIS)) 	Low voltage
64 	Amplifier control signal, cylinders 1 and 4 (Direct Ignition System (DIS)) 	Low voltage
65 	Primary ignition (distributor systems) 	Low voltage
66 	Throttle position sensor (TPS) 	Hose broken
67 	Air Flow Sensor (AFS), hot wire meter (air mass meter) 	Signal is outside normal operation parameters (out of range)
68 	Air Flow Sensor (AFS), hot wire meter (air mass meter) 	Faulty air mass meter signal, incorrect frequency
69 	Air Temperature Sensor (ATS) (MPi only) 	Low voltage
71 	Air Temperature Sensor (ATS) (MPi only) 	High voltage
72 	Amplifier (Direct Ignition System (DIS)) control signal (A+B) 	Lead interruption, open circuit
75 	Torque control (Automatic Transmission (AT) only) 	Low voltage
76 	Torque control (Automatic Transmission (AT) only) 	Continuous
81 	Injector valve 	High voltage
83 	Immobiliser 	No or wrong code
84 	Immobiliser 	No signal
85 	Immobiliser 	Wrong signal
87 	Air conditioning cut-off relay 	Low voltage
88 	Air conditioning cut-off relay 	High voltage
92 	Camshaft sensor 	Faulty hall effect sensor or circuit
93 	Quad drive module (in ECU) 	n/a
Y el 31 no está, así que probablmente en una multec el 31 no aparezca siempre como en las motronic, a las que estamos más acostumbrados.

De todos modos, yo creo que la centralita no está haciendo algo bien, porque efectivamente al arrancar se enciende la luz de fallo de motor y al hacer el autodiagnóstico deberías tener algún fallo almacenado.

Todos esos parpadeos seguidos tampoco son muy habituales.

Yo intentaría quitar la batería unos minutos, que se borre todo lo que tenga la centralita guardado, después arrancar y en cuento se encienda la luz volver a hacer autodiagnóstico. A ver si el resultado es el mismo que lo que te ha salido ahora.