GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LF8) 🢒 DTC P0261, P0264, P0267, P0270, P0273, or P0276

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0261: Injector 1 Circuit Short Low Voltage

DTC P0264: Injector 2 Circuit Short Low Voltage

DTC P0267: Injector 3 Circuit Short Low Voltage

DTC P0270: Injector 4 Circuit Short Low Voltage

DTC P0273: Injector 5 Circuit Short Low Voltage

DTC P0276: Injector 6 Circuit Short Low Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

Fuel Injector Positive Voltage Supply Group 1

P2147

P2146

P2148

Fuel Injector Positive Voltage Supply Group 2

P2150

P2149

P2151

Cylinder #1 Fuel Injector Control

P2147

P0201

P0261, P2148

Cylinder #2 Fuel Injector Control

P2147

P0202

P0264, P2148

Cylinder #3 Fuel Injector Control

P2147

P0203

P0267, P2148

Cylinder #4 Fuel Injector Control

P2150

P0204

P0270, P2151

Cylinder #5 Fuel Injector Control

P2150

P0205

P0273, P2151

Cylinder #6 Fuel Injector Control

P2150

P0206

 P0276, P2151

Circuit/System Description

The engine control module (ECM) calculates the optimum fuel injection on timing using data sent from various engine sensors. The common 1 injector drive circuit is a high-voltage, near 120 volts, which drives injectors for cylinders 1, 2 and 3 in conjunction with the ECM grounding the fuel injector solenoid control circuit. The common 2 injector drive circuit which drives injectors for cylinders 4, 5 and 6 in conjunction with the ECM grounding the fuel injector solenoid control circuit. The ECM also supplies 12 volts at all times to the injector control circuit in order to verify circuit integrity. If the fuel injector solenoid control circuit is shorted to injector drive circuit, DTC P0261, P0264, P0267, P0270, P0273 or P0276 will set, depending upon which cylinder fuel injector circuit failed.

Conditions for Running the DTC
    • The battery voltage is between 10-16 volts.
    • The engine is running.
    • The ignition is ON for longer than 2 seconds.
    • The elapsed time from starter switch OFF is longer than 2 seconds.
    • The CKP sensor is active.
    • The IC watching the CPU in the ECM is normal.
    • The injection drive circuit is normal.
    • The injection pulse width is 0.

Conditions for Setting the DTC

The ECM detects that the fuel injector solenoid coil control circuit is shorted to fuel injector drive circuit during 16 engine rotations.

Action Taken When the DTC Sets

DTCs P0261, P0264, P0267, P0270, P0273 and P0276 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0261, P0264, P0267, P0270, P0273 and P0276 are Type A DTCs.

Diagnostic Aids

An incorrectly installed fuel injector, intermediate connector, will cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Verify the integrity of the fuel injector by inspecting for the following conditions:

    • Damaged components
    • Loose or improper installation

Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

One Fuel Injector DTC Sets

  1. Disconnect the affected fuel injector connector.
  2. Disconnect the ECM connector.
  3. Turn ON the ignition with the engine OFF. Connect a test lamp between the affected fuel injector control circuit and a ground.
    4. ⇒If the test lamp illuminates, test the injector control circuit for a short to voltage.
  4. Test the affected fuel injector circuit for the following:
    5. • An open between the ignition position voltage control circuit splice and the fuel injector connector
    • An open between the ECM and the ignition positive voltage control circuit splice
  5. Test the affected fuel injector for high resistance. Refer to Component Testing in this diagnostic.
    6. ⇒If the circuit does not have a short to voltage or an open, replace the ECM.

Two or More Fuel Injector DTCs Set

  1. Test the affected group injector positive voltage control circuit for an open.
  2. Test the affected fuel injector for high resistance. Refer to Component Testing in this diagnostic.
    3. ⇒If the circuit does not have an open, replace the ECM.

Component Testing

The Injector solenoid coil resistance is about 2 ohms.

⇒If resistance is more than 2 ohms or less than 1.8 ohms at 20°C (68°F), the injector for an open/high resistance. If the tests normal, replace the fuel injector.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Fuel Injector Replacement
    •  Control Module References for ECM replacement, setup, and programming