While driving my 2006 trailblazer ss a engine sign came on with a arrown inside pointing down. which cause my vehicle not to accelerate only up to 40 . what has happen?

Check the serpentine belt.

REDUCED ENGINE POWER: Refer to Engine Control Module Description for the 5.3L engine or Engine Control Module Description for the 6.0L engine
The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The engine control module (ECM) is the control center of this system. The ECM monitors numerous engine and vehicle functions. The ECM constantly monitors the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The ECM also performs the diagnostic tests on various parts of the system. The ECM can recognize operational problems and alert the driver via the malfunction indicator lamp (MIL). When the ECM detects a malfunction, the ECM stores a diagnostic trouble code (DTC). The problem area is identified by the particular DTC that is set. The control module supplies a buffered voltage to various sensors and switches. Review the components and wiring diagrams in order to determine which systems are controlled by the ECM.
Your best bet is take it to a ASE certified repair shop or a Chevy dealer who has the tool to diagnose this problem before it strands you some where .

No it would not ! you probably have a 2-3 Shift Solenoid (SS) problem !
You trailblazer has Vehicle Speed Sensor (VSS) located on the tail shaft of the trans . this sensor supply's info to the PCM for vehicle speed . Your trailblazer also has a Input Speed Sensor (ISS) if this were bad it would cause erratic shifts all gears ! Does your vehicle have a check engine light lit or any other type light like a yellow wrench or service vehicle soon ? Your best bet is to take it to AAMCO or some other ASE certified repair facility !

indicates a failing cam lobe

A manifold gasket leak will cause a power loss everywhere you drive, although a hot engine may lose more power than a cold one. You can check you spark plug color. A manifold leak makes a lean mixture so the plug should show the typical white-ish deposits.

check your engine mount for play as a weak mount causes exhaust to vibrate could also be a heatshield not fitted properly

Check your coolant level, low coolant or air in your cooling system will make a "thud"noise in your heater core when the engine is under load from acceleration. The coolant rushes in to the heater core where the air pocket is trapped and then your hear the noise.
Start with the simple and make sure your coolant level is correct and then try to purge the system to remove the air out for your coolant system.
Thank you for using fixya and good luck

sounds like your lifters or valves are rattling!

ok well try this when it stalls see if spark is present and if it is not and it cools down and starts then you might need to replace ignition control module good luck

You friend broke the low one way clutch. He was rolling backwards and shifted into drive and floored it before the vehicle came to a stop.