I have a 2004 Buick Rendezvous 3.6 I have to shift it manually but cruise control still works

Page 7 right hand side. Specialized oils!

https://sgnauto.com/public/pdf/oil_and_lubricants.pdf

https://www.google.com/search?q=2004+Buick+Rendezvous+AWD+3.4L+oil+for+rear+end+differential+and+rear+transaxle

Service Manuals

https://www.google.com/search?q=2004+Buick+Rendezvous+AWD+3.4L+service+manual

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You buy a harness from the the aftermarket radio shop that supplies you with the new radio.

RADIO - Buick Rendezvous CXL 2004

Automotive Electricians Portal https://portal-diagnostov.com > 2020/04/04 > radio-bu...

Apr 4, 2020 - RADIO - Buick Rendezvous CXL 2004 - SYSTEM WIRING DIAGRAMS Base Radio Wiring Diagram, with Rear Controls. Get Access all wiring diagrams car.

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  Buick Rendezvous CX 2004 - SYSTEM WIRING DIAGRAMS

  https://portal-diagnostov.com > 2020/04/04 > radio-bu...
  Apr 4, 2020 - RADIO - Buick Rendezvous CX 2004 - SYSTEM WIRING DIAGRAMS Base Radio Wiring Diagram, with Rear Controls. Get Access all wiring diagrams car.

2004 Buick Rendezvous Radio Wiring Guide

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Our 2004 Buick Rendezvous radio wiring diagram shows you all the 2004 Buick Rendezvous radio wire colors and what they do. Use our 2004 Buick Rendezvous stereo ...

Buick (2004-2006) Century, Regal, Rendezvous Head Unit ...

PinoutGuide.com https://pinoutguide.com > ... > Buick pinouts
Jan 28, 2022 - OEM radio stereo harness pin assignment. Hardware connector pinouts and cables circuits ...

BUICK RENDEZVOUS 2002-2005 VEHICLE WIRING

JustAnswer https://f01.justanswer.com > BUICK+RENDEZ... PDF WIRING INFORMATION: 2002 Buick Rendezvous. WIRE. WIRE COLOR. WIRE LOCATION. 12V CONSTANT. ORANGE. Ignition Harness. STARTER. YELLOW. Ignition Harness.
5 pages

Check the wire connector that plugs into the cruise control under the hood. Sounds like a loose connection. Remove the and reinsert the wire connector several times to make a better connection. Stepping on the brake pedal disengages the cruise control by a switch on the brake pedal, not the computer.

First off , did you check fluid level ? any lights lit on the instrument cluster, check engine ? How many miles on It ? Ever change the fluid an filter ? can you manually shift through the gears.
DEFINITION: The transmission only provides first and second gear in Drive range. The shift pattern as the vehicle accelerates from a stop is 1-2-2-1. First gear ratio is 2.921:1 and second gear ratio is 1.568:1.
Control Valve Body Assembly
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A faulty 2-3 shift solenoid valve assembly (315B) is stuck On.

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Debris is found in the control valve body (301) or the control valve body spacer plate and gasket assembly (396

Your best bet is to check what is happening by looking at cruise control data in the PCM and BCM. You will need a high end scan tool to do this. It could be as simple as a bad switch in the steering wheel or a brake switch that is bad or out of adjustment..

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Sounds like the cable from the shift lever to the transmission has broken or come loose. You may have to get it towed in to a dealer to have it fixed.

The dealer is blowing smoke up your tailpipe. I couldn't find a manual for the '04, but the '03 and '05 have identical controls for the dash lights, so it's a very good bet the the '04 is the same. Here's a link to the manual for the '05 -- you will find the dash light control on page 3-16.

http://www.extendedgmwarranty.com/owners-manual/buick/2005-Buick-Rendezvous.pdf

P.S. You might want to print the page and confront the dealer with it . . .

HAVE THE DEALERSHIP CHECK IT OUT.YOU HAVE A PROBLEM IN THE SHIFT CONTROL MODULE OR THE SPEED SENSORS.NOT A HOME FIX.

A fuse is broken. Let an expert check to determine this.

Pretty common problem with these. Here's a guide to learn how to fix GM instrument clusters yourself, I used it to fix mine and it worked great.How to guide for GM instrument cluster repair