Have a 2004 gmc yukon getting codes c0040, c0550,c0455,c0296 in the abs computer. Trac and abs light on as well as suspension control.

First you need to have EBCM - electronic brake control module check for DTC'S - diagnostic trouble code's . If the light is on there is a code stored . I think most part stores can do this and for free . After you find out what code is stored , looking up that code in service repair information for diagnostic trouble shooting chart would be next step . There are a few codes too.
DTC C0035 or C0040
DTC C0045 or C0050
DTC C0110
DTC C0131
DTC C0161
DTC C0186
DTC C0196
DTC C0201
DTC C0240
DTC C0241 or P0856
DTC C0244 or P1689
DTC C0245
DTC C0283
DTC C0287
DTC C0290 or C0292
DTC C0455
DTC C0550
DTC C0558

Find the code do the diagnostic's , fix the problem , wiring issue's , a sensor , bad module ,what ever it is . The light will go out then . Here is a sample of code discription .
• DTC C0035 Left Front Wheel Speed Sensor Circuit
• DTC C0040 Right Front Wheel Speed Sensor Circuit

Is your trac light lit ? If so it has a problem an till it is fixed , you can't reset it. Need to have it checked for DTC'S - diagnostic trouble codes .
If the ABS control module detects a malfunction, it will disable TCS and will command the BCM to turn the TRAC LED Off. The driver can also disable TCS, if desired, by depressing the TRAC switch. When the driver depresses the TRAC switch, the ABS control module will disable TCS and will command the BCM to turn the TRAC LED Off.
DTC C0276 TCM Traction Control Not Allowed
DTC C0275 or C0276
The TCM sends a serial data message to the electronic brake control module (EBCM) indicating that torque reduction is temporarily not allowed.
DTC C0550
DTC C0896
The electronic brake control module (EBCM) is required to operate within a specified range of voltage to function properly. During antilock brake system (ABS) and traction control system (TCS) operation, there are current requirements that will cause the voltage to drop. Because of this, voltage is monitored out of ABS/TCS control to indicate a good charging system condition, and also during ABS/TCS control when voltage may drop significantly. The EBCM also monitors for high voltage conditions which could damage the EBCM.

c0040 indicates right front wheel sensor, so problem is more than likely sensor or wiring to it. c0245 indicates wheel speed sensor frequency error. This confirms wheel sensor or wiring.

U1054 is no communication with Rear HVAC control module and is not connected to the Trac Off lt.
Need to have truck scanned and look at ABS and PCM for codes and go from there.

C0040 ABS light on GM Saab Ricks Free Auto Repair Advice

Need to run codes. Can use reader at most auto parts stores. Very likely you have bad sensor at the wheel or something has obstructed the end. Code should tell you which wheel.

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

Chances are one of you wheels lost traction briefly. This would set off a trouble code in the ECM (computer). You can either take it to a shop with a scan tool, and have them reset it (probably cost 50 -75$), or you can disconnect the battery cable (negative side) for 15 - 20 min. This will reset the ECM. Saving you this charge. Best Wishes TJ

C0550 is the code for the ABS module. It is on the frame under the vehicle around the drivers door area. It is a module with all the brake lines coming from it. Reset the trouble codes and see if the problem returns. If it does, the module is not serviceable and will need to be replaced.

The ABS and TRAC lights are on because the system detects a fault with both systems (which share the same components) There may be a bad wheel speed sensor, abs module, even something as simple as a brake switch. The computer will have to be scanned to see what codes were set and then diagnosed further from there to determine what the fault is.