Powertrain Control Module (PCM)
Front left side of the engine compartment, below the air cleaner !
TCM - transmission control module / ECM engine control module together in one module = PCM
TCM
Define turn over , the engine cranks over but doesn't start ? Turn the key to the start position and it does nothing ?
Are any warning lights lit on the instrument cluster , check engine , service vehicle soon , security etc... Look in the engine compartment , under the vehicle for fuel leakage , turn the key on then off to prime the fuel system an look for leaks on top of the engine , fuel pressure regulator ! If the engine does crank over an doesn't start , passably the spark plugs are fuel soaked - fouled !
If the housing is leaking, you can replace the gasket but you need to remove upper filler panel, air cleaner assembly, secondary air injection control valve, oil level indicator tube nut, water pump belt shield, the belt, the radiator hose at housing and then the cover.
If you need to replace the water pump, not easy as you need a special tool to remove and insert the pump.
check manifold gaskets for leaks, check vacuum hoses for leaks. check the transmission oil condition ( auto tranny)
if it is an auto then it may require the pan to come off and check for mechanical fault.
It won't crank over ? Is there a SECURITY light lit on the instrument cluster .
In the under hood fuse / relay box is the start 1 relay , this relay is energized by the PCM - powertrain control module ! This is the relay that controls the starter ! If there is a anti-theft system problem the PCM will not energize the start 1 relay completing the circuit turning on the starter ! . If you knew how you could test right from the start 1 relay socket in the fuse box , rather that just replacing parts ! You can test with a DVOM -digital volt ohm meter or a test light ! Two of the four sockets have battery voltage , one should show ground an the last will show open , this is the control circuit from the PCM .
Chevy Trailblazer no crank testing and information
There is no unlock code - each radio is programmed with the VIN of the vehicle in which it was last installed. The only way to reprogram it to a different vehicle is with a Tech II scan tool (GM Dealer).
The procedure is a bit complicated - the wiper assembly is below the air intake grill at the bottom of the windshield. You need to remove the wipers, the grill cover, the windshield lower retaining frame, the motor retaining bolts, and so on. Best bet is to get a workshop manual for the car for details.
Cleaning the switch is not possible - if it is malfunctioning, it needs to be replaced. You can check the various functions by disconnecting the washer/wiper cable at the bottom of the steering column and checking continuities, but you will need the wiring schematic (shop manual). In the meantime, you should pull the ACCY fuse (15a) in the underhood fuse box.
