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Chris (aka-Moose)
Chris (aka-Moose), GMC Technician
Category: GMC
Satisfied Customers: 44408
Experience:  16 years of experience
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I have a 1999 Denali and the trans is only going into second

Customer Question

I have a 1999 Denali and the trans is only going into second and third gear and reverse my check engine light is on and I got it scan and 3 codes came back
Submitted: 8 months ago.
Category: GMC
Expert:  Gary replied 8 months ago.

can you tell me the code numbers set ?

Customer: replied 8 months ago.
P0740. P0748. P1122. P1810
Expert:  Gary replied 8 months ago.

any access to a multi meter ?

Customer: replied 8 months ago.
Expert:  Gary replied 8 months ago.

start it up and when its acting up and the truck running how many volts are at fuse # ***** called TRANS in the inside fuse box ?

Customer: replied 8 months ago.
It's a 10 amp fuse in number 20 and it's says prndl
Customer: replied 8 months ago.
It read 12.34 volt
Customer: replied 8 months ago.
Is there another fuse box in the truck beside in the driver jam
Expert:  Gary replied 8 months ago.

that is the fuse box

it should be a fuse called trans

Customer: replied 8 months ago.
Here's a pic
Customer: replied 8 months ago.
Did you get the picture I sent
Expert:  Gary replied 8 months ago.

can you unplug the big round transmission connector and with the key ON does the pink wire in that connector show 12 volts ?

Customer: replied 8 months ago.
Where is this connector
Expert:  Gary replied 8 months ago.

passenger front near where the cooler lines connect to the transmission

Expert:  Gary replied 8 months ago.

let me know i have to step out for a few hours i will respond back as soon as i get back

Customer: replied 8 months ago.
Hi I looked all over for that plug n I can't find it can u get me more details on where it is
Customer: replied 8 months ago.
Now I have codes P0713 P0740 P0785 P1860 2nd n 3rd are strong and reverse is strong also
Expert:  Chris (aka-Moose) replied 8 months ago.

Welcome, I'm Chris (aka Moose). I normally log in after 3 pm central. Please make sure to let me know exactly what is needed from me so I can provide EXCELLENT 5 STAR service.

  1. The previous tech has opted out, would you like me to try?
Customer: replied 8 months ago.
Expert:  Chris (aka-Moose) replied 8 months ago.

Great, do you want the GM diag steps for these codes or my thoughts on what is to blame without diag?

Customer: replied 8 months ago.
What's your thoughts I been reading a lot about it and it seems to be stuck in limp mode but when I clear the codes they come rite back . before this happen the trans pan gasket was leaking so the fluid was low so I changed the gasket n fluid n shift solenoid s
Expert:  Chris (aka-Moose) replied 8 months ago.

Thanks, ***** ***** alot of electrical codes for the transmission. I believe your going to find a possible wire or connector issue at or in the trans. ON the trans is a 13 wire connector, can you unplug it and check the connector and pins. Confirm the black wire is a good ground. Confirm the pink wire is power with the key on. If all is good then we need to follow a pinpoint test.

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Thanks Chris

Customer: replied 8 months ago.
I haven't had a chance to check out the truck with the holiday n all but I hope tomorrow or mid week
Expert:  Chris (aka-Moose) replied 8 months ago.

Thanks for the update.

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