GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Controls - 6.6L (LLY) 🢒 DTC P1550

Circuit Description

The fuel injector control module (FICM) activates the fuel injector. The engine control module (ECM) signals the FICM to turn ON the injectors through the fuel injector control circuits. The FICM self monitors the supply voltage whenever the ignition is ON.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1550 Fuel Injector Control Module System Voltage

Conditions for Running the DTC
    • The ignition is ON.
    • DTC U0073 or U0105 are not set.

Conditions for Setting the DTC

The FICM detects low supply voltage.

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 DTC
    • 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 non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Do any other DTCs set?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Important: Use connection pin adapters from J 35616 Adapter Kit.

  1. Turn OFF the ignition.
  2. Disconnect the fuel injection control module (FICM) connectors.
  3. Turn ON the ignition.
  4. Probe the FICM power circuits with a DMM connected to one of the FICM ground circuits.

Does the voltage measure more than 10 volts?

Go to Step 5

Go to Step 4

4

Repair high resistance in the FICM power or ground circuits.

Did you complete the repair?

Go to Step 6

--

5

Replace the FICM. Refer to Fuel Injector Control Module Replacement .

Did you complete the replacement?

Go to Step 6

--

6
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 7

7

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK