Hello and welcome to justanswer.
This problem is fairly common and can be caused by a poor connection in the vehicle harness. I have included the details below in a technical service bulletin. Please let me know if you have additional questions.
Bulletin No.: 03-08-45-003D
Date: February 24, 2006
Subject:Reduced Power, Stuck in High Gear, SES Light On, DTCs P0223, P0504, P0700, P1228, P1271, P1280, P1599, P1779, P1791, P2119, P2101, P2128, P2135, or P2138 Set, Speaker Buzz Noise, HVAC Inoperative (Inspect/Replace Corroded or Bent Terminals)
Models:2005-2006 Chevrolet Equinox2006 Pontiac Torrent2002-2003 Saturn VUE
This bulletin is being revised to update an illustration. Please discard Corporate Bulletin Number 03-08-45-003C (Section 08 - Body and Accessories).
Some customers may comment that the vehicle is exhibiting one or more of the following conditions:
These conditions may be intermittent. Diagnostic Trouble Codes (DTC) P0223, P0504, P0700, P1228, P1271, P1280, P1599, P1779, P1791, P2119, P2101, P2128, P2135, or P2138 may also be present.
The instrument panel/body inline connector (black 40-pin electrical connector), located behind the left hinge pillar garnish molding, may have bent or corroded terminals.
Disconnect and inspect the instrument panel/body inline connector (black 40-pin electrical connector). If necessary, replace damaged terminals and apply dielectric grease to the connector.
Yes, this could very well be part of the problem. This connector is not sealed and water coming into the vehicle can get into the connector and cause a bad connection. There is an additonal bulletin that basically says the same thing the first one did, but is more general in nature. I do believe this is your problem. You will need to repair the connector and then find out where the water is leaking into the vehicle.
Bulletin No.: 07-06-04-019D
Date: June 28, 2010
Subject: Intermittent Malfunction Indicator Lamp (MIL) Illuminated, DTC P2138 with Reduced Engine Power (Repair Instrument Panel (IP) to Body Harness Connector)
Models: 2005-2011 GM Passenger Cars and Light Duty Trucks (Including Saturn)2005-2009 HUMMER H22006-2010 HUMMER H32005-2009 Saab 9-7X
Supercede:This bulletin is being revised to update the model years and warranty information. Please discard Corporate Bulletin Number 07-06-04-019C (Section 06 - Engine/Propulsion System)
This condition may be caused by water intrusion into the instrument panel (IP) to body harness connector, which carries the APP sensor signals to the ECM/PCM. This water intrusion results in a voltage difference between APP Sensor 1 and APP Sensor 2 that exceeds a predetermined value for more than a calibrated period of time, setting P2138.
Note Aftermarket equipment can generate DTC P2138 and/or other DTCs.