GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 Engine 🢒 Engine Controls - 2.5L (LBK) 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

The engine control module (ECM) controls the ignition coils by pulsing the ignition control (IC) circuits, which triggers an ignition coil and ignites the spark plug. The ECM controls the sequencing and the timing of each ignition coil. The ignition system consist of the following components:

    • The 6 ignition coils
    • The crankshaft position (CKP) sensor
    • The camshaft position (CMP) sensor
    • The ECM

The ignition coils use the following circuits:

    • An IC circuit
    • An ignition 1 voltage circuit
    • A ground circuit

Test Description

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

  1. This step tests for a short to ground in the ignition 1 voltage circuit.

    2.

  2. This step tests for a fault in the ignition 1 voltage circuit. It is necessary to command the fuel pump relay ON, because the fuel pump relay supplies the voltage to the ignition coils. When the fuel pump is commanded ON, the test lamp will pulse On and OFF.

    3.

  3. This step test for a fault in the ground circuit of the ignition coil.

    4.

  4. This step test for a fault in the IC circuit of the ignition coil.

    5.

  5. This step tests for high resistance. Five ohms or more can cause can cause a driveability condition.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connect 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

Important: Do not perform this diagnostic procedure if you were not sent here from a misfire DTC or the Engine Cranks but Does Not Run diagnostic.

Attempt to start the engine?

Does the engine start and idle?

--

Go to Step 3

Go to Step 11

3

Is DTC  P0301-P0306 set?

--

Go to Step 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Remove the fuel pump fuse from the underhood fuse block.
  3. Remove the engine cover.
  4. Disconnect the appropriate ignition coil.
  5. Turn ON the ignition, with the engine OFF
  6. Probe the ignition 1 voltage circuit of the ignition coil with a test lamp connected to a good ground. Refer to Probing Electrical Connectors in Wiring Systems.
  7. Command the fuel pump ON, with a scan tool.

Does the test lamp turn ON and OFF?

--

Go to Step 5

Go to Step 12

5
  1. Turn OFF the ignition.
  2. Connect the test lamp between the ignition 1 voltage circuit and the ground circuit of the ignition coil.
  3. Turn ON the ignition, with the engine OFF
  4. Command the fuel pump ON, with a scan tool.

Does the test lamp turn ON and OFF?

--

Go to Step 6

Go to Step 14

6
  1. Connect the DMM between the ignition control (IC) circuit and a good ground.
  2. Set the DMM to the DC 4 Hertz scale. Refer to Measuring Frequency in Wiring Repairs.
  3. Observe the DMM while cranking the engine.

Is the frequency more than the specified value?

10 Hz

Go to Step 8

Go to Step 7

7

Test the ignition control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find a condition with the circuit?

--

Go to Step 15

Go to Step 10

8

Test for high resistance in the following circuits of the ignition coil.

    • The ignition 1 voltage circuit
    • The IC circuit
    • The ground circuit

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the resistance more than the specified value?

4 ohms

Go to Step 13

Go to Step 9

9

Test for an intermittent and for a poor connection at the ignition coil. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

10

Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

11

Important: The ignition 1 voltage circuit is shared with other components. Disconnecting a component on the shared ignition 1 voltage circuit may isolate a shorted component. Review the electrical schematic and diagnose the shared circuits and components.

  1. Repair the open or the short to ground in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the fuse as necessary.

Did you complete the repair?

--

Go to Step 18

--

12

Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

13

Repair the high resistance in the affected circuit of the ignition coil. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

14

Repair the open or high resistance in the ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

15

Repair the open or high resistance in the IC circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 18

--

16

Replace the ignition coil. Refer to Ignition Coil Replacement .

Did you complete the replacement?

--

Go to Step 18

--

17

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

18
  1. Connect all disconnected components.
  2. Start the engine.
  3. Operate the system in order to verify the repair.

Did you correct the condition?

--

Go to Step 19

Go to Step 2

19

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