No start after transmission was replaced

MCDONALDSBOI

MEMBER
2002 CHEVROLET SILVERADO
4.8L
V8
4WD
AUTOMATIC
250,000 MILES

I have just got my transmission replaced at a shop, got the truck home and it will not start. The starter tested good, relay tested good, brand-new park neutral safety switch, and brand-new charged battery. The truck runs and drives fine but in order to start it you have to first turn key on and flip to start position then leave it on "on" position then open fuse box under hood go to starter relay underside of it is a yellow wire going into number 30 or 85 spot can't remember but send a positive signal to that wire from the battery and starts every time. I'm stuck unless there's a magical sensor or hidden switch I'm missing. Once it is started it's all good, everything works normally until you shut it off and turn it back on.

8 Replies

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

I'm not sure which pin you supply with power, but it has to be direct to the S terminal on the starter. That is what engages the starter motor.

So, either we have a power issue to the relay, a bad relay, or a faulty ground for the relay.

If you haven't already, check the ignition A fuse in the under-hood fuse box. In addition to checking the fuse, confirm there is power to it. Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If that fuse checks good, check the crank fuse in the interior fuse panel. Follow the same directions as listed above.

If they are good, then next locate the black wire from the starter relay. Check it for continuity to ground. The ground (G106) is located at the right front of the engine. Make sure it is good.

If that is good, switch the starter relay with another relay having the same part number. See if that changes things. If there, isn't one having the same part number, here is a link that explains how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

I attached the wiring schematic below as a reference for you. Pic 3 shows the under the dash fuse box and pic 4 is the under the hood fuse box. I highlighted which fuses to check.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.

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Saturday, March 19th, 2022 AT 9:44 PM

MCDONALDSBOI

MEMBER
5 POSTS

I have checked all of the fuses, they are all good, that was the first thing I checked and the relay is good. I bought a new one to be sure and tested it as well. Both are good. I even tried both in a different slot still worked and the G106 ground is in good working order I have even cleaned the connection to make sure there wasn't even a slight issue with it. Could it be wiring to or from the park neutral position switch? The switch is brand-new and adjusted right. I just don't know which wire is power in and which is signal wire.

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Sunday, March 20th, 2022 AT 3:25 AM

JACOBANDNICKOLAS

MECHANIC
109,772 POSTS

Hi,

The purple wire with the white tracer is the supply. That power supply depends on the ground mentioned to complete its circuit. Once complete, the relay reacts by closing the circuit to the starter (S terminal) and engaging the starter.

Check to see if there is power at the purple/white wire at the relay. This will require the key to be in the start position, so you will likely need a helper.

Take care and let me know what you find.

Joe

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Sunday, March 20th, 2022 AT 5:43 PM

MCDONALDSBOI

MEMBER
5 POSTS

The purple wire with the white tracer has power when the key is switched to start, and the ground has good connection to ground. I am still at a loss I have no idea where to check. I tested the relay again and it's still good it seems to get power to where it needs it but when I turn the key to start still no relay click and no crank.

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Monday, March 21st, 2022 AT 7:31 AM

MCDONALDSBOI

MEMBER
5 POSTS

I found it out I took a relay apart and was diagnosing it that way as I don't have another way to test the fuse box the purple with white was getting crank signal but was not transferring power into the relay. I jumped pins 87 and 30 and she fired right up with the key. So, my problem is a bad fuse box. I guess now I have a bunch of new parts that won't need to be replaced for a while. Thanks for the help.