unknown codes

Hi anyone like to shed some light on what these codes are?
U1026 Loss of Class 2 Communication with ATC
U1041 Loss Of EBCM Communication.
Truck is a '99 Silverado 4x4, 5.3l
Codes were read with a Tech 2. My mechanic friend pulled the codes for me but didn't know what they were, said he'd look them up but didn't have time ATM. Just thought someone else might know something.. I'm going to do some checking on google later.
THANKS!
Adair
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http://www.regalgs.org/obd2.htm
http://pcm.dxsoftware.com/dtcs.htm
This is what a google search digs up.
-- ---------------------------------------------------------------- Ed Murray Certified Locksmith My Enthusiast's Website: http://www.crooked-ridez.com

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Inline...........

Automatic transmission controller <?>

Electronic Body Control Module
Sounds like you have some computer issues dude.
Doc
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For some reason Automatic Transfer Case was the first thing that came to my mind.. but it could be either or.

http://www.gmtcny.com/serial%20data.html calls it an Electronic Brake Control Module. so whos right? I've seen the Body Control Module thing more. anyway, if anything on that site is true it's pretty interesting.

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In-inline............

Could be, hence the <?> after my guess.

Dunno. Sorry. These are oddball codes that I've never seen before.
Doc
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DTC U1026 Loss of ATC Class 2 Communication Circuit Description The class 2 circuit connects to various modules. These modules monitor the link for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules on the data link. When a module receives a critical operating parameter from another module, the receiving module records the identification number from the module that sent the message. This is called State of Health Monitoring (SOH). A critical operating command will have the sending module's identification number attached with it. Once an identification number is learned by a module, it will continue to monitor for that number. When no message is detected from a learned identification number for a set time, a code is set in the module that was monitoring the identification number.
Conditions for Running the DTC a.. The ignition voltage is greater than 9.5 volts, but less than 18.0 volts. b.. DTCs U1300 and U1301 are not set. Conditions for Setting the DTC a.. A message from a learned identification number is not detected. b.. All conditions met for 5.0 seconds. Action Taken When the DTC Sets a.. The PCM stores the DTC information into memory when the diagnostic runs and fails. b.. The Malfunction Indicator Lamp (MIL) will not illuminate. c.. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. Conditions for Clearing the MIL/DTC a.. A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. b.. A last test failed (Current DTC) will clear when the diagnostic runs and does not fail. c.. Use a scan tool in order to clear the MIL/DTC. Diagnostic Aids
Important The communication DTCs are for information only. Refer to Scan Tool Does Not Communicate w/Class 2 Data Line in Wiring Systems for further diagnosis.
This DTC will not set unless the modules have already established communications.
DTC U1041 Loss of EBCM Communication Circuit Description The class 2 circuit connects to various modules. These modules monitor the link for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules on the data link. When a module receives a critical operating parameter from another module, the receiving module records the identification number from the module that sent the message. This is called State of Health Monitoring (SOH). A critical operating command will have the sending module's identification number attached with it. Once an identification number is learned by a module, it will continue to monitor for that number. When no message is detected from a learned identification number for a set time, a code is set in the module that was monitoring the identification number.
Conditions for Running the DTC a.. The ignition voltage is greater than 9.5 volts, but less than 18.0 volts. b.. DTCs U1300 and U1301 are not set. Conditions for Setting the DTC a.. A message from a learned identification number is not detected. b.. All conditions met for 5.0 seconds. Action Taken When the DTC Sets a.. The PCM stores the DTC information into memory when the diagnostic runs and fails. b.. The Malfunction Indicator Lamp (MIL) will not illuminate. c.. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records. Conditions for Clearing the MIL/DTC a.. A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. b.. A last test failed (Current DTC) will clear when the diagnostic runs and does not fail. c.. Use a scan tool in order to clear the MIL/DTC. Diagnostic Aids
Important The communication DTCs are for information only. Refer to Scan Tool Does Not Communicate w/Class 2 Data Line in Wiring Systems for further diagnosis.
This DTC will not set unless the modules have already established communications.
Scan Tool Does Not Communicate w/Class 2 Data Line Step Action Value(s) Yes No For a full view of the schematic refer to Data Link Connector (DLC) Schematics . 1 Can the scan tool be powered up? -- Go to Step 9 Go to Step 2 2 1.. Disconnect the scan tool from the data link connector, (DLC). 2.. Inspect for a proper connection of the scan tool to the data link at terminals 4 and 16. Is the connection good? -- Go to Step 3 Go to Step 5 3 Measure the voltage from terminal 16 of the DLC to ground. Is voltage within the specified range? 12.0 -14.8 V Go to Step 4 Go to Step 7 4 Measure the resistance from terminal 4 of the DLC to ground. Is resistance within the specified range? 0-5ohms Go to Step 6 Go to Step 8 5 Repair the connection as needed. Is the repair complete? -- System OK -- 6 The scan tool may be malfunctioning. Refer to the scan tool instruction manual. Has a properly operating scan tool been obtained? -- Go to Step 1 -- 7 Repair the open in CKT 640 (ORN). Is the repair complete? -- System OK -- 8 Repair the open in CKT 1850 (BLK). Is the repair complete? -- System OK -- 9 1.. Turn the ignition switch to RUN. 2.. Using the scan tool, attempt to establish communication with each module on the class 2 data link: a.. ATC b.. IPC c.. VCM/PCM d.. EBCM e.. BCM 3.. If using a Tech 2, the Class 2 Message Monitor feature can be used in order to obtain this information Are there any modules on the class 2 data link which are communicating? -- Go to Step 10 Go to Step 13 10 Are DTCs U1000 and/or U1xxx (Lost Communications With XXX) set in the modules which will communicate? -- Go to Step 11 Go to Step 12 11 Diagnose the malfunction using the class 2 communication malfunction (U1000) or the class 2 lost communication with XXX (U1xxx) procedures as appropriate. Is the procedure complete? -- System OK -- 12 Diagnose the malfunction using the class 2 lost communication with XXX (U1xxx) procedures for the module which is not communicating. Is the procedure complete? -- System OK -- 13 1.. Turn the ignition switch to OFF. 2.. Inspect for proper connection of the scan tool to the data link at terminal 5. Is the connection good? -- Go to Step 14 Go to Step 5 14 Measure the resistance from terminal 5 of the DLC to ground. Is resistance within the specified range? 0-5ohms Go to Step 15 Go to Step 30 15 Inspect for a proper connection of the scan tool to the data link connector at terminal 2. Is the connection good? -- Go to Step 16 Go to Step 5 16 1.. Disconnect splice pack 205 (SP205). Refer to Data Link Connector (DLC) Schematics . 2.. Inspect for a proper connection of the class 2 serial data circuit to terminal A of the splice pack. Is the connection good? -- Go to Step 17 Go to Step 5 17 Measure the resistance from terminal 2 of the DLC to terminal A of the splice pack. Is the resistance within the specified range? 0-5ohms Go to Step 18 Go to Step 29 18 Measure the resistance on the DLC from terminal 2 to terminal 4. Is the resistance as specified? OL (Infinite) Go to Step 19 Go to Step 28 19 1.. Turn the ignition switch to RUN. 2.. Measure the voltage on the DLC from terminal 2 to terminal 4. Is the voltage within the specified range? 0-1 volt Go to Step 20 Go to Step 27 20 1.. Turn the ignition switch to OFF. 2.. Using the correct terminal adapter from J 35616-A, connect a jumper wire to terminal A of the splice pack 205 (SP205) which is connected to a module. 3.. Connect the other end of the jumper wire (with the correct terminal adapter) to a terminal in the SP205 which is connected to a module. 4.. Turn the ignition switch to RUN. 5.. Using the scan tool, attempt to establish communication with the module which is jumpered to the DLC. Can communication be established? -- Go to Step 21 Go to Step 22 21 Repeat step 20 for each module on the Class 2 serial data link. Can communication be established for each module on the Class 2 serial data link? -- Go to Step 31 Go to Step 22 22 1.. Turn the ignition switch to OFF. 2.. Disconnect the module which does not communicate. 3.. Measure the resistance from the SP205 terminal of the Class 2 serial data circuit for the disconnected module to ground. Is the resistance as specified? OL (Infinite) Go to Step 23 Go to Step 28 23 1.. Turn the ignition switch to RUN. 2.. Measure the voltage from the Class 2 serial data circuit of the disconnected module to ground. Is the voltage within the specified range? 0-1 volt Go to Step 24 Go to Step 27 24 1.. Turn the ignition switch to OFF. 2.. Inspect the connector of the disconnected module in the area of the class 2 serial data circuit for backed out terminals which would cause a short to ground or voltage. Are all terminals properly locked into the connector body? -- Go to Step 25 Go to Step 5 25 1.. Replace the module which does not communicate. Refer to the appropriate On-Vehicle Service procedures from the following list for the module being replaced in order to ensure a complete repair. a.. Body Control Module Replacement in Body Control Systems b.. Instrument Panel (IP) Cluster Replacement in Instrument Panel, Gauges and Console c.. Electronic Brake Control Module (EBCM) Replacement in Antilock Brake Systems d.. VCM Replacement/Programming in Engine Controls - 4.3L e.. PCM Replacement/Programming in Engine Controls - 4.8L, 5.3L, 6.0L f.. Transfer Case Shift Control Module Replacement in Transfer Case - NVG 246 - NP8 (Two Speed Automatic) 2.. Reconnect the SP205. Refer to Data Link Connector (DLC) Schematics . 3.. Reconnect all the modules on the class 2 serial data link. 4.. Turn the ignition switch to RUN. 5.. Using the scan tool, attempt to establish communication with the module which was replaced. Can communication be established? -- Go to Step 31 Go to Step 26 26 Replace the class 2 serial data circuit wire between the splice pack 201 (SP201) and the module which does not communicate. Refer to Data Link Connector (DLC) Schematics . Is the repair complete? -- Go to Step 1 -- 27 1.. Turn the ignition switch to OFF. 2.. Repair the short to voltage in the class 2 serial data circuit. Refer to Data Link Connector (DLC) Schematics . Is the repair complete? -- Go to Step 31 -- 28 Repair the short to ground in the class 2 serial data circuit. Refer to Data Link Connector (DLC) Schematics . Is the repair complete? -- Go to Step 31 -- 29 Repair the open in the class 2 serial data circuit. Refer to Data Link Connector (DLC) Schematics . Is the repair complete? -- System OK -- 30 Repair the open in CKT 451. Refer to Data Link Connector (DLC) Schematics . Is the repair complete? -- System OK -- 31 1.. Reconnect the SP205. 2.. Reconnect all the modules on the Class 2 serial data link. 3.. Turn the ignition switch to RUN. 4.. Wait for 10 seconds. 5.. Inspect for DTCs in each module on the class 2 serial data link. Are there any DTCs which begin with a U set with a current status? -- Go to Step 33 Go to Step 32 32 Are there any DTCs which do not begin with a U set? -- Go to Step 33 Go to Step 34 33 Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction. Is the procedure complete? -- Go to Step 34 -- 34 Have all the DTCs been diagnosed? -- Go to Step 35 Go to Step 33 35 Clear all the DTCs. Is the procedure complete? -- System OK --

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Thanks Ed.
Adair
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