DTC P1223, P1226, P1229, P1232, P1235, P1238, P1241, or P1244. GMC Truck TopKick C-Series (Conventional) C4/C5 2004

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 6.6L (LLY) 🢒 DTC P1223, P1226, P1229, P1232, P1235, P1238, P1241, or P1244

Circuit Description

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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

•	DTC P1223 Injector 1 Output Circuit

•	DTC P1226 Injector 2 Output Circuit

•	DTC P1229 Injector 3 Output Circuit

•	DTC P1232 Injector 4 Output Circuit

•	DTC P1235 Injector 5 Output Circuit

•	DTC P1238 Injector 6 Output Circuit

•	DTC P1241 Injector 7 Output Circuit

•	DTC P1244 Injector 8 Output Circuit

Conditions for Running the DTC

•	The engine is running.

•	The ignition voltage is between 6-18 volts.

Conditions for Setting the DTC

•	The ECM detects that the command state and the actual state of the control circuit does not match.

•	The condition exists for less than 1 second.

Action Taken When the DTC Sets

•	The control module stores the DTC information into memory when the diagnostic runs and fails.

•	The malfunction indicator lamp (MIL) will not illuminate.

•	The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.

•	The driver information center, if equipped, may display a message.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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 than 4 fuel injector control circuit DTCs set, a short to voltage on a fuel injector control circuit is likely the cause of the concern. A short to voltage will set more than 4 fuel injector control circuit DTCs.

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 2, 3, 5, 8. If there is only 1 fuel injector DTC set, an open circuit, poor connector, or short to ground is likely the cause of the concern. Refer to DTC Descriptors in order to determine which cylinder is causing the condition.

This step verifies the ECM is supplying the appropriate frequency (Hz) through the fuel injector control circuits to the FICM. If the DMM displays 2-4 Hz while cranking, inspect for a poor connection at the FICM.

This step is testing for a short to ground on a fuel injector control circuit. If the test lamp illuminates on any fuel injector control circuit, a short to ground is the cause of the condition.

This step is testing for a short to a voltage. If the DMM displays a voltage greater than the specified value, a short to voltage is the cause of the condition.

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Engine Controls?	--	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Start and idle the engine. Monitor the DTC Failed This Ignition parameter with a scan tool. Do any of the DTCs P1223-1244 fail this ignition?	--	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records data for this DTC with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition?	--	Go to Step 4	Go to Intermittent Conditions
4	Are DTC P1223, P1232, P1238, and P1241 ALL set?	--	Go to Step 9	Go to Step 5
5	Are DTC P1226, P1229, P1235, and P1244 ALL set?	--	Go to Step 9	Go to Step 6
6	Turn OFF the ignition. Disconnect the harness connector C1 of the fuel injection control module (FICM). Important: Use the J 35616-94 Connector Adapter of the J 35616 to probe the FICM connector. While cranking the engine, measure the frequency of the appropriate fuel injector control circuit with a DMM. Refer to Measuring Frequency in Wiring Systems. Is the voltage frequency more than the specified value?	2.9 Hz	Go to Step 12	Go to Step 7
7	Turn OFF the ignition. Disconnect harness connector C2 of the engine control module (ECM). Test the appropriate fuel injector control circuit for an open or short to another affected fuel injector control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 16	Go to Step 8
8	Turn OFF the ignition. Verify the harness connector C2 of the ECM is still disconnected. Probe the affected fuel injector control circuits with a test lamp connected to battery voltage. Refer to DTC Descriptors and Probing Electrical Connectors in Wiring Systems. Does the test lamp illuminate on any of the fuel injector control circuits?	--	Go to Step 10	Go to Step 15
9	Turn OFF the ignition. Disconnect the harness connector C2 of the ECM. Turn ON the ignition, with the engine OFF. Measure the voltage from each of the fuel injector control circuits with a DMM. Refer to Probing Electrical Connectors in Wiring Systems. Is the voltage more than the specified value on any of the fuel injector control circuits?	1 V	Go to Step 11	Go to Step 15
10	Test the appropriate fuel injector control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 16	Go to Step 13
11	Test the appropriate fuel injector control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	--	Go to Step 16	Go to Step 14
12	Inspect for poor connections at the harness connector of the FICM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	Go to Step 16	Go to Step 14
13	Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	Go to Step 16	Go to Step 15
14	Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement?	--	Go to Step 16	--
15	Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement?	--	Go to Step 16	--
16	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC run and pass?	--	Go to Step 17	Go to Step 2
17	Observe the stored information with a scan tool. Does the scan tool display any DTCs that you have not diagnosed?	--	Go to Diagnostic Trouble Code (DTC) List	System OK