Question about 2006 Chevrolet Trailblazer

1 Answer

<!-- from fixya rte -->How do I fix class 2 link malfunction - 2006 Chevrolet Trailblazer

Posted by on


1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Chevrolet Master
  • 14,644 Answers

What are we talking about here ? class 2 serial data bus , Do you have a scan tool ? Have a U code ? Something not working correctly ?

Posted on Nov 27, 2014


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.

Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

2 Answers

My Buick 2004 rendevous,my door ajar light stays on and it dings, and the locks, lock and unlock a the while when driving

Probably the switch input to the BCM is bad . door ajar switch .
The BCM is also capable of commanding other vehicle systems to control functions that are not directly wired to and/or controlled by the BCM. The BCM accomplishes this task by sending specific messages on the class 2 serial data link. The vehicle system capable of performing such function will respond to the BCM message.
The BCM controls/monitors the following functions:
• Audible warnings
• Indicators control
• Interior lighting
• Exterior lighting
• Power/automatic door locks
• Keyless entry
• Content theft deterrent
• Personalization
• Serial Power Modes
• Electrical Power Management

Audible Warning
The body control module (BCM) provides the following audible control functions. Some audible control functions may be controlled by other systems through the class 2 serial data link:
• Headlamp on reminder
• Key in ignition reminder
• Personalization mode
• Delay locking indication
• Keyless entry programming/diagnostic mode indication

Indicator Control
The body control module (BCM) provides the following indicator control functions through the class 2 serial data circuits. Some indicator control functions may be controlled by other systems through the class 2 serial data link:
• Door ajar
• Liftglass/endgate ajar
• Park brake
• High beam
• Park lamp malfunction
• Service vehicle soon
• Personalization mode
• Security LED
• Battery

Door Locks Go Crazy 1
Door Locks Go Crazy 2
Door Locks Go Crazy 3

Dec 05, 2017 | Buick Cars & Trucks

2 Answers

2001 buick century stalled without warning. tried to restart, but wouldnt crank, no fuel pump noise, no click. had power to radio, heater fan, flashers but not dashboard lights (prndl, fuel gauge).

Make sure battery has a full charge and battery connections all good. Check fusible links where applicable. Any component that doesn't work and is fuse protected, not only check the fuse, check the fuse circuit for voltage, use a test lite.
The wiring diagram is for starter circuit, you can see the fuses. Any testing for starter motor, make sure tranny is in park or neutral and parking brake is set. It is possible to jump crank relay to see if starter motor will crank, but, that doesn't mean it will start. Make sure vehicle can't move.


Nov 21, 2016 | 2001 Buick Century

1 Answer

Inadv and rap 1 clicks when I try to start a 2002 Tahoe

Did you check for BCM codes
DTC B1477
Retained Accessory Power Circuit Low
DTC B1478
Retained Accessory Power Circuit High
DTC B1397
Device Voltage Reference Out #1 CKT Low
DTC B1398
Device Voltage Reference Out #1 CKT High
Charging system check ?

Diagnostic System Check - Retained Accessory Power
Test Description
The numbers below refer to the step numbers on the diagnostic table.

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

  2. This step is checking for DTCs in the BCM.

  3. This step is checking for RAP specific DTCs.






Install a scan tool.

Does the scan tool power up?
Go to Step 2
Go to Scan Tool Does Not Power Up in Data Link Communications


  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the body control module.

Does the scan tool communicate with the BCM?
Go to Step 3
Go to
Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications


Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the Class 2 Power Mode on the Scan Tool. Refer to the Serial Data Power Mode table within the Body Control System Description and Operation in Body Control Systems, for a list of the power mode states that correspond to each ignition switch position.

Does the Class 2 Power Mode parameter reading match the ignition switch position for all the selected positions?
Go to Step 4
Go to Power Mode Mismatch in Body Control System


Select the BCM display DTCs function on the scan tool.

Does the scan tool display any DTCs?
Go to Step 5
Go to the Symptoms list in the appropriate service category


Does the scan tool display B1477 or B1478?
Go to
Diagnostic Trouble Code (DTC) List
Go to Symptoms - Retained Accessory Power

May 10, 2016 | Cars & Trucks

1 Answer

Why does my 2003 Aztec show error on the odometer and won't start?

The IPC calculates the mileage based on the vehicle speed signal circuit from the powertrain control module (PCM). The odometer will display ERROR if an internal IPC memory malfunction is detected or there is a class 2 communication fault. The odometer displays either miles or kilometers as requested by the activation of the English/metric button on the driver information center (DIC). The associated indicator (km or MI) illuminates.
You probably have A class 2 serial data communication malfunction. All the Modules on your vehicle talk, share information on the data network an if something brings it down ,shorts it out, the vehicle will not start .
The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The DLC is a standardized 16 way connector located below the instrument panel and close to the steering column. Both the connector design and location are dictated by industry wide agreements. All DLCs are required to provide a power supply, hot at all times, to terminal 16. This circuit is used to power the scan tool. All DLCs supply a power ground at terminal 4 and a signal ground at terminal 5. The class 2 serial data circuit is provided at terminal 2 of the DLC.
You probably need to take this to a ASE certified repair shop or the a GM dealership ! Because if you are asking here you probably don't know about this stuff, an you sure don't have a factory scan tool to see which modules have DTC'S - diagnostic trouble codes stored .

May 21, 2015 | 2003 Pontiac Aztek

1 Answer

Fixes for non-communicating OBD II port and nonworking trunk release button on driver door panel?

What pins did your friend jump in the DLC ,2 an 4 ? they don't call it ALDL any more ! Does the vehicle start an run ?
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:
Scan tool power battery positive voltage at terminal 16.

Scan tool power ground at terminal 4.

Common signal ground at terminal 5.

Class 2 signal at terminal 2.

I wonder how many friends out there mess up other friends vehicles from stuff they see on the internet . When are you people going to learn , your messing with complex electronics !!!!! He shorted out the class 2 serial data communication network !
Do you know what this is ? if not you need to take to your local GM Mr. goodwrench !
Class 2 Serial Data Link
The data link is configured as a ring with discrete lines entering and leaving each module. This allows communications to the modules on the ring if one of the two discrete circuits is open.
A total list of the control modules on the Class 2 Serial Data Line can include the following:
Dash Integration Module (DIM)

Driver Door Module (DDM)

Electronic Brake Control Module (EBCM)

Head Up Display (HUD) w/UV6

HVAC Control Module w/C67

Inflatable Restraint Sensing and Diagnostic Module (SDM)

Instrument Panel Cluster (IPC)

Instrument Panel Integration Module (IPM) w/CJ2

Memory Seat Module (MSM) w/A45

Powertrain Control Module (PCM)


Rear Integration Module (RIM)

Remote Control Door Lock Receiver (RCDLR)

Remote Playback Device - CD Changer w/U1S

Theft Deterrent Control Module

Vehicle Interface Unit (VIU) w/UE1

Power door serial data does not communicate with the scan tool via the DLC. Power door serial data information is interpreted by the driver door module (DDM) and transmitted on the Class 2 data link by the DDM.
Power door serial data is used for serial data communication between the four door modules as well as the driver door switch assembly (DDSA
Scan Tool Does Not Communicate with Class 2 Device
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes.
The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

  1. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.

  2. The DTC U1300, U1301, and U1305 may be retrieved with a history status. These DTCs are not the cause of the present condition.

  3. A State of Health DTC with a history status may be present along with a U1000 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.

Apr 22, 2015 | 2001 Buick LeSabre

1 Answer

How do I fix a serial 2 data link malfunction on a 4 cylinder 99 sunfire

Hey John ! how's it going ? How do you know you have a class 2 data bus problem ? Need some more info ! Do you have a scan tool ? Can't communicate with the PCM ? Have a check engine light on ?
You may access 2 data lines with the scan tool. The serial data line UART (circuit 800) allows the following components to communicate via serial data:
The scan tool

The powertrain control module (PCM)

The instrument panel cluster

The sensing diagnostic module (SDM)

The electronic brake control module (EBCM)

The serial data line class 2 (circuit 1807) allows the scan tool to access directly the PCM in order to read emissions-related information. The scan tool gains access to both data lines through the data link connector (DLC). You may then monitor or control system operations for diagnostic purposes.

Mar 08, 2015 | 1999 Pontiac Sunfire

1 Answer

Engine light is on and code is u1255 class 2 communication malfunction

Class 2 communication is 2 wire system that run to all the modules in the car ranging from mirrors to seats radio HVAC and more the malfunction occurs when one of the modules has lowered the operating voltage in the circuit . very expensive equipment needed to repair or pinpoint its location. suggest dealer repair.

Apr 16, 2014 | 2003 Chevrolet Silverado 2500HD

1 Answer

U1000 class 2

Does the scanner give you any other read outs ?

Feb 10, 2014 | Buick Cars & Trucks

1 Answer

Et1505an code reader comes up with link error every time i try to scan my 04 f-150 is it the scanner or my truck if it is my truck what is the cause. How would I fix it ?

The only way to find out if it is the code reader or the truck is to plug in another code reader or scan tool and see if it gives you the same results (try this first).

NOTE: Generic OBD code readers will operate ONLY on the Class 2 data link. A true scan tool will operate on BOTH the Class 2 and the UART lines. Accessing the onboard computer system with a scan tool may give you a fault code that indicates that the Class 2 circuits may be malfunctioning.

To diagnose onboard computer network communications malfunctions, the proper equipment that can communicate with the ENTIRE network must be used. Please note that generic OBD code readers cannot perform this function.

Apr 28, 2012 | 2004 Ford F150

1 Answer

1998 Cadillac STS with IPM U1255 code history. what does this code mean?

U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)

here is a link to all of the codes for your caddy

Aug 20, 2009 | 1998 Cadillac Seville

Not finding what you are looking for?
2006 Chevrolet Trailblazer Logo

79 people viewed this question

Ask a Question

Usually answered in minutes!

Top Chevrolet Experts


Level 3 Expert

79865 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22326 Answers

Ronny Bennett Sr.
Ronny Bennett Sr.

Level 3 Expert

6927 Answers

Are you a Chevrolet Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides