Check engin light ON straight after changing a timing belt

[sqa]

Hi, a mechanic changed my Mazda Protege 2003 (2.0L 206,000 km) timing belt with a pump and after 1-2 h. of driving the check engine light came on.
I came to the mechanic back, he checked the code and it is like - not enough fuel. He checked all wires, vacuum lines and everything seemed to be fine. He re-set the code, but after 2 days the light came up again.
I will come to see him again, but to cut the exploration time probably somebody had already the similar problem and knows the reason or may suggest one?
Thanks

[goldstar]

Can you tell us the specific code number? It would help to narrow down the problem.

Happy Motoring!

[sqa]

Mechanic said the code is P0171 (running lean or something like these).

Thanks

[goldstar]

P0171 Fuel Trim system too Lean

According to the FSM, likely causes are:
Misfire
O₂ (front) deterioration or heater malfunction
PRC solenoid valve malfunction
Pressure regulator malfunction
Fuel pump malfunction
Fuel filter clogged or restricted
Fuel return hose clogged
Fuel line leakage
Leakage from exhaust system
Purge solenoid valve malfuntion
Purge solenoid hoses improperly connected
Insufficient compression

I would check the O₂ sensor first.

Happy Motoring!

[vw.fe2o3]

See also:
http://www.obd-codes.com/p0171

[vw.fe2o3]

So this is weird. Exactly 14 days ago I replied to this thread with a link for the OP to read. So today, my car just tossed me this same code p0171 on the way to work
Anyway, I just went out for a break to poke around and found my air intake hose is cracked wide open. Not too pricey.