the ABS module might have bad solder joints internally or bad connections to it. some people have been able to remove the module from the ABS and open it to resolder the pins.

this video is for an avalanch but the module is similar

 

DTC C0550
Circuit/System Description
The electronic brake control module (EBCM) detects an internal malfunction.
Conditions for Running the DTC
The ignition switch is in the ON position.
Conditions for Setting the DTC
An internal EBCM malfunction exists.
Action Taken When the DTC Sets
One or more of the following actions may occur:

The EBCM disables the Antilock Brake System (ABS)/Traction Control System
(TCS)/Vehicle Stability Enhancement System (VSES) for the duration of the ignition cycle.

The dynamic rear proportioning (DRP) may be disabled and the Brake Warning indicator
may turn ON.

The Stability Caution indicator turns ON.

The DIC displays the SERVICE STAB SYS message.

The DIC displays the TRACTION FAILED message.
Conditions for Clearing the MIL/DTC

The condition for the DTC is no longer present and the DTC is cleared with a scan tool.

The EBCM automatically clears the history DTC when a current DTC is not detected in 100
consecutive drive cycles.
Circuit/System Verification
DTC C0550 will set as result of internal EBCM circuit failure.

Replace the EBCM.

 

as described hummerz previous post.

Food for thought, the 03 GM service manual itself doesn't expand DTC's, however the 2005 manual does and interestingly C0550 lists the following:-


So the code is ambiguous i.e. it depends which module generated the code.

According to the manual, either the ASM, BCM or EBCM (not TCSM) will turn on the ABS, + Brake Warning + TC indicators.

However a TCSM fault will only set the SERVICE 4WD indicator and position LED, and not allow shifting (so in theory it can't be that)

To summarize, DTC C0550 with ABS indicators etc. could be either:-

• ASM (Assembly, Accelerator and Servo Control Module
• BCM (Body Control Module)
• EBCM (Electronic Brake Control Module)

For the EBCM the GM manual also expands the fault description slightly:-For the ASM and BCM the description for C0550 is as follows:-

Circuit Description
The internal fault detection is handled inside the control module. No external circuits are involved.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0550 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC
The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

Conditions for Setting the DTC
• The control module detects an internal write malfunction.
• The control module detects an internal checksum malfunction.

Action Taken When the DTC Sets
If equipped, the following module specific actions may occur:

• The ABS indicator turns ON.
• The BRAKE warning indicator turns ON.
• The traction control system (TCS) indicator turns ON.
• The electronic brake control module (EBCM) disables the ABS/dynamic rear proportion (DRP)/TCS.

Conditions for Clearing the DTC
• A current DTC clears when the malfunction is no longer present.
• A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids
• This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
• If this DTC is retrieved as both a current and history DTC, replace the module.
• If this DTC continues to set intermittently, replace the module



BTW did you keep your old EBCM?

It's unlikely to have two modules with the exact same fault.

I'd be tempted to get someone with a TECH2 to find out which module generated the DTC just to be sure.

 

Thank you so much for all the information!!! I believe it is the ABS Module…. I initially installed that module on my old hydraulic brake unit and thats when all the lights and message came on… my plan is to drive it with all the lights and messages, especially since the 4wd system seems to be working properly… im hoping the computer will reset itself after a specific number of restarts with no problems…. If it doesn’t reset by the spring, which should be plenty of restarts I will remove the ABS Module and sent it that repair center that was sent to me in an earlier post… any thoughts on that plan???

 

The computer will clear itself when repaired! In the meantime put some tape over the lights and drive around WITHOUT ABS/TCS. Can be challenging on icy/snow covered roads.

 

This is what the GM manual says:-
Conditions for Clearing the DTC
• The condition for the DTC is no longer present and you used the scan tool Clear DTC function.
• The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

So you need to use a scan tool to clear the code, only the history is cleared after 100 drive cycles.

If you have an Android Phone and need a cheap way to check/clear the codes, you can buy an ELM 327 Mini Bluetooth Dongle on Amazon and download TORQUE from the Google App store (either Lite or buy Pro)

This will let you read the DTC's and clear them however the capability of an ELM is limited, it won't tell you which ECU generated the code

Just make sure the ELM Supports J1850 (there are dozens on Amazon)

Not sure what's available for iPhones

 

Oh if you clear the code and it comes back on straight away--- you have an urgent issue that needs to be resolved, it's your brakes!

 

Try googling "C0550" or GMC C0550"

 

A current DTC clears when the malfunction is no longer present.

 

Newer transmission was installed, newer used motor installed new fusebox, after all this the lights have came on and scanner will not connect to vehicle to get codes as to what’s going on… seems that all started after fusebox replacement, fusebox brand new from GM….Any ideas