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Had a P0601. Replaced computer with new reprogrammed unit. Getting the crank relearn code which is normal. The issue is this.

Unhooked battery to R&R computer. Hooked battery back up. When the switch is turned to the crank position all of the lights go out. Return switch to run position and everything lights back up. No attempt at turning over at all.

VATS/Passlock has been deactivated on the new computer. I did do the key cycle dance just in case with no luck.

Started engine up before the R&R and fired off fine. Thought the battery might have gotten low so I hooked up jumper cables to another running vehicle and it still does the exact same thing.

Items replaced:
Engine and transmission computer
Ignition switch module

First thought would be an issue with the new computers, but the vehicle did this also before when I unhooked the battery with the original ECM. After sitting for a couple of days it started, so I suspect it isn't the new computers.

Temps in the 30's when this all occurred.

All functions in the vehicle still work (alarm, locks, windows, radio, etc).

At a loss and hope someone here knows what it can be.

Thanks in advance.


   
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Location: Oregon
on your truck, your key does not power up the starter solenoid. Your ignition switch sends a signal to the power control module and the PCM starts the engine.

first thing you should look at is fuse #34, IGN A. It is a 40A fuse that in in the underhood fuse box. It powers through the starter relay to go to the starter solenoid. If the fuse is good and has battery voltage, go to next step. Your starter relay in the underhood fuse panel. starter relay 47. Have someone try to start the engine while you have your finger on the relay. When the key is put in the start position you should feel the relay click. Try it a few times. If you don't feel the relay click switch it with another relay that is the same and try again. If the engine cranks with the different relay then you have a bad relay. if it still doesn't click then you need to check the contacts in the fuse box that go to the starter relay. Make sure the fuse IGN E (#22, 10A) has battery voltage in run and start. Check fuse CRANK FUSE (#17, 10A) has battery voltage in start. Make sure the trans shifter is in park or neutral. Your computer is looking for all those things. When it sees all those things, it will ground the starter relay to complete the circuit and pull the contact to bridge the circuit to send power to the starter solenoid and crank the engine over.

now you can bypass most of all that by using a remote starter switch from the battery to the starter solenoid just to check to see if that will crank the engine or use a relay bypass the will plug into where your relay goes in and it will crank the starter as long as it is inserted. (you pull the relay when you want it to stop)

what type of equipment do you have to check the circuits for the starter relay?


   
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Used my DVM and tested the fuses. All test good. When the key is cycled I can hear the throttle body but nothing on the started. Cannot feel the starter relay engauge when the key is turned to the start position. Swapped it out for the blower relay and same thing.


   
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if all the fuses are good (and there are no missing fuses) then your pcm is not grounding the starter relay. Follow the wiring diagram to see what part is missing to the starter relay.


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