I have a 2003 gmc envoy 4wd I have codes co237, co236 my abs light is on what does this mean

When the 4WD Service light comes on it means that the Transfer Case Control Module (TCCM) has not received the proper feedback from the two actuators that control the 4WD engagement. The system needs to be diagnosed by a technician.

C0237 is related to the rear speed sensor and C0267 is related to the pump motor in the ABS system.

They are connected thru the body computer. IE, if you are in 4wd and a problem develops with the ABS the system will go into limp mode.
You will need to get the codes scanned to find out where to start.

I am guess you mean P error codes.. There is no C error codes

P0237: Turbo/Super Boost Sensor A Circuit Low Input
P0268: Cylinder 3 Injector Control Circuit High
P0269: Cylinder 3 Contribution Balance Fault
P0287: Cylinder 9 Contribution Balance Fault
P0711: Trans Fluid Temp Sensor A CKT Range/Perf

you need to replace the tccm and get it programmed.


2-04-21-006E: Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set No Communication with TCCM (Reprogram Transfer Case Control Module) - (Jul 20, 2006)
Subject: Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set, No Communication with TCCM (Reprogram Transfer Case Control Module) Models: 2004 Buick Rainier 2002-2004 Chevrolet TrailBlazer, TrailBlazer EXT 2003-2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe 2002-2004 GMC Envoy, Envoy XL 2003-2004 GMC Sierra, Yukon, Yukon XL 2004 GMC Envoy XUV 2002-2004 Oldsmobile Bravada with Electronic Shift or Active Transfer Case (RPOs NP1, NP4 or NP8)

This bulletin is being revised to add Subject information and change the labor operation. This bulletin cancels and supersedes Bulletin Number 03-04-21-006. Please discard Corporate Bulletin Numbers 02-04-21-006D and 03-04-21-006 (Section 04 -- Driveline/Axle).
ConditionSome customers may comment that the 4WD/AWD indicator lights on the selector switch do not work, or the 4WD/AWD system may be inoperative and/or the service 4WD light is illuminated. The condition is typically intermittent and always occurs at key-up. Upon investigation, the technician may find DTC C0550 set.
CauseThe Transfer Case Control Module (TCCM) has not received the wake-up call during key-up and has remained in the "sleep mode".
When the TCCM is in the "sleep mode", it will not communicate with the class II bus or the Tech 2®.
Correction

1. Try to communicate with the TCCM. If no communication, go to step 2. If communication is possible, go to step 5.
2. Remove the underhood (ATCM or TREC) TCCM fuse.
3. Wait 30 seconds.
4. Reinstall the fuse. The module should "wake up" and communicate with the Tech 2®.
5. Check for codes in the TCCM. If a C0550 is found current or in history with or without other codes, replace the module and go to step 6.
6. Reprogram the TCCM with the latest TIS software using normal SPS procedures.
7. Verify operation and that no codes are present.

Important: For the 2002 model year, the TCCM must be replaced and reprogrammed.
Warranty Information

Have your ABS Wheel Sensor checked, it is mounted on the hub of your axle. it could have gotten dirt on it or it is bad and it is not giving a signal to the ABS Module.

Are you not getting a check engine light ? Take your suv to auto zone and get them to check it for codes and post the codes I will check back later to see what codes you posted they will help in finding the problem. Thank you

If you need further help, I’m available over the phone at https://www.6ya.com/expert/edward_020b3320326d263d

Ask a garage to reset your computer, could be a recurring trip fault causing the car to shut down.

Clearing it might solve the problem - if not, the fault codes will tell you what the problem is!

The check valve is #12619128 and the gasket is #24577193. I think $65 and $75 respectively you can try websites like parts4chevy.com and gmpartsdirect.com. 
your talking about the diverter valve for the AIR pump. In which case it is easy to do and its easily accesible in the engine bay. The valve is located at the passenger side by the transmission dipstick tube under the intake tube. Good luck

My 2005 Envoy 4WD is not working. Switc is currently on 2HI, but light is showing AWD. What is the problem???