My BCM in my Chevrolet Express 2500 (2011) was broken in june. I installed a new one and now he is broken already again. My dealer doesn't know how it is possible but I'm afraid that the problem isn't solved. Anyone ideas ????

Chevrolet Fuel Pump Driver Problems Where Is The Broken Wire

The BCM - body control module controls turn signals . There is no flasher unit . Your best bet would be to take your vehicle to the dealer !
Turn Signal Lamps
The BCM 3, BCM 5, and BCM 6 fuses located in the underhood fuse block supply battery voltage to the body control module (BCM) for turn signal, hazard lamp, and stop lamp operation. Voltage from the BCM 5 fuse used for the front and rear left turn signals, voltage from the BCM 3 for the right front turn signal, while voltage from the BCM 6 fuse is used for the right rear turn signal. When the turn signal switch is place in either the LEFT or RIGHT position, ground from G303 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a message via GMLAN to the instrument panel cluster (IPC) to cycle the turn signal indicator ON and OFF depending on the position of the turn signal switch.

Ignition ON, observe the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the left turn signal ON and OFF. The reading should change between Active and Inactive.

Man, I believe BCM located under dash above the drivers right knee area. You can call the Dealer to verify as I am not positive on that year. Check the attached links,instruction and guides, Good luck
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https://www.gmupfitter.com/files/media/photo/67/2008_LD_ElectricalFullSizeVans.pdf

Try to get the fault codes and checked what codes does it means

You can't reprogram it. Dealer only. If the fuse block has the BCM on it, Try using your old BCM. Otherwise you have to buy a new BCM and have it programmed. BCM's can only be programmed one time for your car.

the remote entry lock module, ensure the Body Control Module (BCM) is correct for your 2002 CHEVROLET TRAILBLAZER with a 4.2L engine. Special restrictions like "California only" or "with sport package" may indicate a Body Control Module (BCM) fits only certain 2002 CHEVROLET TRAILBLAZER models.
the bcm has to be programmed by a dealer,go to your dealer to make sure that is the problem,it could also be the ignition switch,it usually mimics a bad bcm,a switch is cheaper.

take it to an accredited service center that has experience on your make of car and discuss the problem with them

I would say no. You have the resistor key for the ignition, right? The bcm is programmed to read that resistance or it will not enable the start relay.

You've already eliminated #3 and #6, so keep checking...

Priority Action Part Type Cause
1 Inspect Radiator Cooling System Clogged.
2 Inspect Radiator Radiator Fins Obstructed.
3 Inspect Radiator Cap Worn or Damaged Radiator Cap.
4 Inspect Radiator Fan Motor Faulty Fan Motor.
5 Inspect Belt Incorrectly Routed, Adjusted (Tensioned), Missing or Worn Drive Belt(s).
6 Inspect Thermostat Faulty Thermostat.
7 Inspect Water Pump Worn, Cracked or Leaking Water Pump.
8 Inspect Radiator Fan Relay Intermittent Failure

Check for a 40 amp blown fuse for the BCM this controls those 2 unit. If this checks ok disconnect the BCM module and plug back in this will reset it the BCM is located under the Drivers side kick panel against the firewall. If it work after the BCM reset replace the BCM it will work only temporaraly.