I would try clearing the codes and disconnecting the modification in yor electric system. If they donot come back then it's being caused by your modification.
<H1>DTC P1223, P1226, P1229, P1232, P1235, P1238, P1241, or P1244</H1><A name=ss1-1386729><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss1-1386729" target="_blank">
<H5>Circuit Description</A></H5>
The engine control module (ECM) enables the appropriate fuel injector on the compression stroke for each cylinder. The ECM controls the fuel injection control module (FICM) by grounding the control circuit via a solid state device called a driver. The ECM monitors the state of the driver. If the ECM detects an incorrect voltage for the commanded state of an injector driver, DTCs P1223, P1226, P1229, P1232, P1235, P1238, P1241, or P1244 will set.<A name=ss2-1386729><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss2-1386729" target="_blank">
<H5>DTC Descriptors</A></H5>
This diagnostic procedure supports the following DTCs:
<UL =BULLET>
<LI>DTC P1223 Injector 1 Output Circuit
<LI>DTC P1226 Injector 2 Output Circuit
<LI>DTC P1229 Injector 3 Output Circuit
<LI>DTC P1232 Injector 4 Output Circuit
<LI>DTC P1235 Injector 5 Output Circuit
<LI>DTC P1238 Injector 6 Output Circuit
<LI>DTC P1241 Injector 7 Output Circuit
<LI>DTC P1244 Injector 8 Output Circuit </LI>[/list]<A name=ss3-1386729><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss3-1386729" target="_blank">
<H5>Conditions for Running the DTC</A></H5>
<UL =BULLET>
<LI>The engine is running.
<LI>The ignition voltage is between 6-18 volts. </LI>[/list]<A name=ss4-1386729><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss4-1386729" target="_blank">
<H5>Conditions for Setting the DTC</A></H5>
<UL =BULLET>
<LI>The ECM detects that the command state and the actual state of the control circuit does not match.
<LI>The condition exists for less than 1 second. </LI>[/list]<A name=ss1-727822><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss1-727822" target="_blank">
<H5>Action Taken When the DTC Sets</A></H5>
<UL =BULLET>
<LI>The control module stores the DTC information into memory when the diagnostic runs and fails.
<LI>The malfunction indicator lamp (MIL) will not illuminate.
<LI>The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
<LI>The driver information center, if equipped, may display a message. </LI>[/list]<A name=ss1-727824><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss1-727824" target="_blank">
<H5>Conditions for Clearing the MIL/DTC</A></H5>
<UL =BULLET>
<LI>The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
<LI>A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
<LI>A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
<LI>Clear the MIL and the DTC with a scan tool. </LI>[/list]<A name=ss5-1386729><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1386729&psdid=437&evc=sm#ss5-1386729" target="_blank">
<H5>Test Description</A></H5>
The numbers below refer to the step numbers on the diagnostic table.
[list=1]<A name=TD04>
<LI value=4>
This step determines if there are 4 fuel injector control circuit DTCs set in a group. A short to voltage will set 4 fuel injector control circuit DTCs for cylinders 1, 4, 6, 7, or cylinders 2, 3, 5, 8. Refer to DTC Descriptors in order to determine which cylinders are affected. If there are more t