98 k2500 4l80e neutral park safety switch question

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Ranchtruck805

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Greetings Ranchtruck805,

@xXxPARAGONxXx beat me to it, but we're in agreement that the General's
Factory Service Manuals are by far the best documentation available.



That's a good troubleshooting approach, for you have eliminated everything after the
Starter Relay from the troubleshooting table. Here's a few troubleshooting tips in
this area that you might find useful:

1) I took a bird's eye view pic of the Underhood Fuse/Relay box. If you look closely you
can see that all the big square relays are the exact same part number:

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This is a troubleshooter's delight, for we can substitute a suspect relay with a known-good neighbor
in order to figure out if the problem is the relay itself vs. something upstream feeding it.

And here's the legend on the underneath of the cover for the Underhood Fuse Block:

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****

Let's assume that you swapped the fuel pump & starter relay. If the problem follows
the relay, then we have the proof we need to buy the replacement with confidence.

On the other hand, IF the problem stays in the Starter Relay socket, then we
need to figure out if we are experiencing a 'control voltage' to the relay vs a 'power to solenoid'
issue? In order to make this easier to troubleshoot, here's the same sheet, but
crayoned up 2 different ways:

Starter Relay circuit, Control Side

{Fuse 6 > Ignition Switch > Fuse 8 > Neutral Safety Switch > Starter Relay Pin 86 > Pin 85 > G105}

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Note: Colored the involved schematic lines to match color code



Starter Relay circuit, Power delivery side

{IGN A Fuse 6 > Starter Relay Pin 30 > Pin 87 > Starter Solenoid}

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Note: Colored the involved schematic lines to match color code.

So now to figure out if the Starter Relay Control Circuit, *or* the Underhood IGN A Fuse 6 Power to Starter Solenoid circuit
is bad. I know that you've already jumped +12v power to the socket for Pin 87 & it started,
but did you do this straight from the battery, or did you jump from Pin 30 to Pin 87?

If jumpering Pin 30 to Pin 87 works, and (temporarily) swapping in the Fuel Pump relay
doesn't fix it, then working through the control path is going to locate the root cause of not
being able to crank the engine over from behind the wheel.

Best of luck!
Thank you so much Road Trip, I have not jumped pin 30 to pin 87 yet.
What I have done is check voltage from the ignition switch(Check the yellow wire at the ignition switch and when I turn the key I see 12v in the start position> next I checked the #8 crank fuse 10 amp fuse in the fuse block inside the cab I see 12v as well continuity I check the neutral park safety range switch and as of now the only wire that I am getting voltage out of is either a pink wire or purple( the wires are discolored) I will do a continuity test to verify what wire it is.
And as you motioned I applied direct 12v to pin 87 and my truck did start and keep idling with the key on the run position of course.
I haven't had time to check the truck when I get a chances ill do some more diag work on my truck. I am so close to figuring this out. I cant wait.
Thanks guys!
 

Ranchtruck805

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Hello everybody, I wanted to follow up with you guys. Fortunately the rain stopped in California and I was able to work on my truck. I replaced the neutral safety range pigtail connector. I noticed that there was continuity problem. The previous owner had replaced the pigtail connector for the neutral safety range switch, but he had the wire colors off as well as there was an open in his crimp work. I ended up getting an AC Delco OEM pigtail connector for my truck and bingo. I was back to starting the truck with my key. I want to thank you guys for giving me some good knowledge. Hopefully this helps somebody.
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