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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Got a 2000 gmc 454 w a no start condition

Customer Question

got a 2000 gmc 454 w a no start condition
Submitted: 1 year ago.
Category: Chevy
Customer: replied 1 year ago.
unit will crank for about 5 secs and relay kicks out and it quits turning over.we hav checked and have no spark.we sent pcm out and had it tested to come back ok.we have power to pink wires at the coil packs.we have replaced crank sensor and ohm wires to pcm. cam sensor distributor turns.fuel pump works.
Expert:  GM Tech (Cam) replied 1 year ago.
Hi there, I am Cam. When you try to start, can you spray fuel in the throttle body and does it start?
Customer: replied 1 year ago.
have no spark. i have read alot online about crank position sensor
Expert:  GM Tech (Cam) replied 1 year ago.
The crank sensor is VERY common. Let me ask this, have you checked spark out of the coil or just at the wires/plugs??
Customer: replied 1 year ago.
both.this has coil packs.
Expert:  GM Tech (Cam) replied 1 year ago.
Ok, so at the crank sensor, do you have power on 1 wire and ground on another?
Customer: replied 1 year ago.
yes we do.
Expert:  GM Tech (Cam) replied 1 year ago.
Dont suppose you have a scanner that can view live data?
Customer: replied 1 year ago.
yes and i have.i can c tps, coolant temp but no rpm while cranking.is the crank sensor adjustable. i notice to screws. one to hold it and one to go up and down maybe
Expert:  GM Tech (Cam) replied 1 year ago.
No it should not be.
Customer: replied 1 year ago.
scanner is not showing any rpm
Expert:  GM Tech (Cam) replied 1 year ago.
Replace your crank sensor next and see what happens.
Customer: replied 1 year ago.
we have replaced it.and check wheel for loosness and it turning
Expert:  GM Tech (Cam) replied 1 year ago.
Ok, Broken wiring between the sensor and the ECM?
Customer: replied 1 year ago.
no we have ohm them and put a load on them
Expert:  GM Tech (Cam) replied 1 year ago.
OK, any loose pins at the ECM or the crank sensor?
Customer: replied 1 year ago.
no no loose pins. any other sensors that would tell unit to have no spark. we have been thru schamatics. checked powers and grds to ecm also.thats why we removed pcm sent it out and it tested ok. i still not convinced it is ok
Expert:  GM Tech (Cam) replied 1 year ago.
Trying to pull the GM manuals, what is the Vin?
Customer: replied 1 year ago.
1GDM7H1B8YJ520234
Expert:  GM Tech (Cam) replied 1 year ago.
Ok, what happens if you unplug the cam sensor? Do you get spark?
Also what is the RPM with the scanner, IAT, TPS voltage, ECT?
Customer: replied 1 year ago.
ok unpluged cam sensor and no spark. to make sure i am right the cam sensor is in the look alike distributor correct? im showing no rpm on scanner. ECT is 59. IAT is 63. i cant see tps voltage but can watch the percentage go from 14.5 to 100. O2 sensors. voltage i can c and its .445 . i also read about a TAC module behind glove box.what is that. to make sure u know this is a gmc c7500 medium duty truck
Expert:  GM Tech (Cam) replied 1 year ago.
Yes, I was able to find that with the vin which helps. So no RPM signal makes me think wiring or PCM. The crank sensor is monitored directly by the PCM.
Customer: replied 1 year ago.
is there a reading or voltage return signal to the ecm that i can back probe it at ecm to c if its gettn there from the crank sensor. i would need the pin out locations. c we have worked on this unit a while then sat a while and now im on it again. we r a big guard rail company with alot of gmcs but this is only one like this and this year.we sent pcm out and was tested ok but like i said im not convinced.
Expert:  GM Tech (Cam) replied 1 year ago.
Actually its a frequency sent back. I would back probe the dark blue white in the red connector pin 44.
Customer: replied 1 year ago.
what r the other 2 pins for the crank sensor at the pcm. i would like to check the wires again. we had to return the manual we was borrowing. and do u have any other suggestions. or even know where we cold get a good pcm to try on unit
Expert:  GM Tech (Cam) replied 1 year ago.
Power and ground. Here is the diagram.