GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Diagnostic System Check - Engine Controls

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more inspection/maintenance (I/M) system statuses that did not set.

Step

Action

Yes

No

1

Perform the following preliminary inspections:

    • Ensure that the battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.
    •  Ensure that the battery cables are clean and tight.
    •  Inspect the easily accessible systems or the visible system components for obvious damage or conditions that could cause the symptom. Refer to Strategy Based Diagnosis in General Information.
    •  Ensure that the engine and control module grounds are clean, tight, and in the correct location.
    •  Inspect for aftermarket devices that could affect the operation of the system. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Ensure the resistance between the engine control module (ECM) housing and the battery negative cable is less than 0.5 ohms.

Did you find and correct the condition?

System OK

Go to Step 2

2
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the ECM.

Does the scan tool communicate with the ECM?

Go to Step 3

Go to Data Link References in Data Link Communications

3

Important: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode.

  1. Access the Class 2 Power Mode in the Diagnostic Circuit Check on the scan tool.
  2. Rotate the ignition switch through all positions while observing the ignition switch power mode parameter. Refer to Body Control System Description and Operation in Body Control System for a list of the power mode states that correspond to each ignition switch position.

Does the ignition switch parameter reading match the ignition switch position for all switch positions?

Go to Step 4

Go to Power Mode Mismatch in Body Control System

4

Attempt to start the engine.

Does the engine crank?

Go to Step 5

Go to Symptoms - Engine Electrical in Engine Electrical

5

Did the engine start and idle?

Go to Step 6

Go to Engine Cranks but Does Not Run

6

Important: Do NOT clear the DTCs unless instructed by a diagnostic procedure.

  1. Select the DTC display function for the engine control module and record the DTCs.
  2. If multiple powertrain DTCs are stored, diagnose the DTCs in the following order:
    3. 2.1. Test for component level DTCs. For example, sensor DTCs, solenoid DTCs, and relay DTCs

    Begin with the lowest number DTC unless the diagnostic table directs you otherwise.

    2.2. Test for system level DTCs. For example, misfire DTCs, EVAP system DTCs and fuel trim DTCs.
  3. If there are any powertrain DTCs, Select Capture Info in order to store the Powertrain DTC information with a scan tool.

Does the scan tool display any DTCs?

Go to Step 7

Go to Step 10

7

Does the scan tool display DTCs which begin with a "U"?

Go to Data Link References in Data Link Communications

Go to Step 8

8

Does the scan tool display DTCs P0601, P0602, P0604, or P0606?

Go to DTC P0601, P0602, P0603, P0604, P0605, P0606, P0607, P1600, P1621, P1627, P1680, P1681, P1683, or P2610

Go to Step 9

9

Does the scan tool display DTCs P0560, P0562, P0563, P0625, P0626, or P1668?

Go to Diagnostic Trouble Code (DTC) List in Engine Electrical

Go to Diagnostic Trouble Code (DTC) List

10

Are there any transmission control module (TCM) DTCs or any automatic transmission symptoms?

Go to Diagnostic System Check - Automatic Transmission in Automatic Transmission - Allison

Go to Step 11

11

Is the customer's concern with inspection and maintenance (I/M) testing?

Go to Inspection/Maintenance (I/M) System Check

Go to Step 12

12

Are there any engine controls or driveability symptoms observed?

Go to Symptoms - Engine Controls

System OK