NO CRANK AND NO START FOR VEHICLE DIAGNOSED FROM WIRING DIAGRAM

no crank and no start for vehicle from wiring diagram. this explains how to troubleshoot a no crank situation from a relay. jumping the load side of the relay will activate the relay however in this circuit both the control side and the low side will be activated. reason being you have to start the ignition switch which gives 12 volts to both circuits in the relay.

[@randywheeler652]

Awesome Joe. Have question on a 2005 buick century. Intermittent when I tap key to start takes about 5 attempt before starting. It goes click click click but starts eventually. Since it starts I know park neutral switch is ok. Ignition switch is ok. Fuses are good. Input from key goes to computer and another relay in computer scences crank and sends signal to crank relay. I'm going to do a voltage drop at starter and have battery checked. Do you think Joe this could be a problem in the computer?

[@believeitornot101]

So are you having difficulty with a crank and no start or a no crank and no start makes a difference do you hear the engine trying to turn over these pumps fuel pumps need high fuel pressure to start sometimes 60 PSI sometimes you have to put the accelerator pedal all the way down to start the car

[@randywheeler652]

A intermittent no crank joe. When it acts up you rotate key to start maybe up to 5 times and you hear a click click click then on like 6th attemp it fires right up.I know all fuses are good, the park neutral switch is good. Could it be the relay in the pcm going bad. Doesn't one the security modules sees the chip in the key send a signal to start relay in pcm then on the purple wire to the crank relay and it allows starter to crank hope I explained that right

[@believeitornot101]

@@randywheeler652 I don't have the schematic in front of me measure the load side of the starter on the relay if you see my video usually I put a piece of wire in the terminal of the relay then I crank this will tell you if you're getting a computer signal and the relay is activated which is the less last step before to start a motor if you have a clamp meter you can put around the starter motor wire and see if you are cranking amps

[@randywheeler652]

I don't have a amp clamp yet Joe but I'll try that. I'm going to make sure my battery terminals are clean tomorrow and do a voltage drop at starter. Then have the parts store check cranking amps draw of my starter then do just as you directed me to do joe. I love watching your videos, makes things a whole lot easier to diagnosis for me. Thank you so much

[@believeitornot101]

@@randywheeler652 if there is corrosion on the cables or terminals you could do a voltage drop test or a resistance test across all of the cable good luck