2021 GMC Yukon XL Denali NO CRANK NO START

[TXWELDER]

2021 Yukon XL Denali with 6.2. Trans went out last Tuesday, in the shop Wednesday and out Friday. Wife drove it minimally SAT-MON and parked at a store then no crank/no start. Had it towed home.

-She got a message stating "service charging system, vehicle may stall", P0622, I believe a P0615 starter relay or solenoid code and about 15 others that were generic stating "see owners manual for definition".

-It randomly asked her to roll the driver and passenger side windows up and down.

-Battery has 12.8V and was charged overnight to confirm it's condition.

-I cannot find any loose/missing/burned/frayed/disconnected wiring or harnesses anywhere.

-I tested every fuse in the box and the battery top fuses are good also.

-I attempted to bypass the starter relay to see if it would turnover and it does nothing.

-Lights work, radio works.

-Oddly only the driver side auto folding step will come down.

Not wanting to throw parts at it, looking for any advice.

 

[Fless]

That first code indicates something wrong with the field connection for the alternator. I would inspect alternator connections carefully and have the alternator tested.

P0622 Generator Field F Control Circuit Malfunction

How to easily diagnose, repair, and info on causes of a P0622 trouble code that indicates a detected failure of the generator lamp F control circuit.

www.obd-codes.com

 

[Jimmyy]

If the Transmission was out and in so was the starter. I would start there. Checking the cable at the starter visually and with a meter. Check for voltage drop from the battery to the starter (large cable), and check to see if it's getting the command (smaller wire) to start. You'll may need a helper for this. Best of luck and hopefully a Merry Christmas.

 

[blanchard7684]

those are an alternator charging circuit code and a starter relay circuit code.

Without a wiring diagram I am speculating that they are somehow interconnected.

I would start with carefully checking the wiring connections on alternator.

Then checking the connections on the starter.

Ground wire on starter?

 

[TXWELDER]

Thank you, everyone. After Christmas I will take a deeper dive at the alternator and starter and update any findings.

 

[TXWELDER]

Merry Christmas!

UPDATE:

Two things I was incorrect about in my initial post, one being that the code is a P0617 not a P0615 and the other is that I was bypassing the starter pinion relay instead of the starter motor relay to try and test the starter. I do in fact hear a click when using a jumper wire on the starter motor relay plug but it is very faint and not turning the engine over. Does anyone know if both of those relays need to be energized to engage the starter?

I used a breaker bar on the engine and was able to confirm it does turn over, so not another seized up 6.2L. This gives me hope that I just have a failed starter and could be back on the road soon.

I suppose it could be the battery top bus bar as I see it called out in these situations, but I have continuity across all of those connections. I have no way to verify correct amperage is getting to the starter to turn it.

I will also confirm 12v on leg 85 of the starter relay connection to verfy the ignition switch is working as it is supposed to.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[TXWELDER]

Resolved. Transmission shop left loose connections at the starter, all is now working as designed.

 

[blanchard7684]

Resolved. Transmission shop left loose connections at the starter, all is now working as designed.

Figured as much. Well done tracking problem down.

And a major thanks for following up.

 

[Fless]

In hindsight a simple voltage drop test would have indicated the problem:

 

[jfoj]

How many miles on your 2021 when the trans failed?

 

[TXWELDER]

How many miles on your 2021 when the trans failed?

111,*** miles