GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2004 🢒 Century 🢒 Engine 🢒 Engine Electrical 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

The ignition control module (ICM) has independent power and ground circuits. The circuits between the ICM and the powertrain control module (PCM) consist of the following circuits:

    • The IC timing signal
    • The IC timing control
    • The low-resolution engine speed signal
    • A low reference signal

The ICM sends 3X signals to the PCM. The ICM controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions:

    • The PCM receives the second 3X signal.
    • The PCM applies 5 volts to the IC timing signal circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Disconnect the crankshaft position (CKP) sensor A.
  2. Observe the 3X crank sensor parameter with a scan tool.
  3. Crank the engine.

Does the scan tool indicate a 3X crank sensor signal present?

--

Go to Step 3

Go to Crankshaft Position Sensor System Diagnosis

3
  1. Remove the fuel pump relay with the J 43244 Relay Puller Pliers.
  2. Connect the CKP sensor A.
  3. Test for spark at each cylinder with a J 26792 HEI Spark Tester.

Did you have spark on all cylinders?

--

Go to Step 4

Go to Step 6

4

Does the spark tester indicate a bright blue spark on all cylinders?

--

Go to Step 5

Go to Step 6

5
  1. Remove the spark plugs.
  2. Examine the spark plugs for any abnormal conditions or damage. Refer to Spark Plug Inspection .

Are the spark plugs in good condition?

--

System OK

Go to Step 12

6
  1. Turn OFF the ignition.
  2. Connect the J 26792 to the spark plug wire of the inoperative cylinder.
  3. Switch the inoperative spark plug wire connection with a known good cylinder at the ignition coils.
  4. Crank the engine.

Do you have spark on the inoperative cylinder?

--

Go to Step 7

Go to Step 9

7
  1. Disconnect the spark plug wires from the inoperative ignition coil.
  2. Measure the secondary resistance of the ignition coil.

Is the resistance within the specified range?

5,000-8,000 ohms

Go to Step 8

Go to Step 10

8
  1. Remove the inoperative ignition coil.
  2. Connect a test lamp between the control circuits of the ignition coil on the ignition control module (ICM).
  3. Crank the engine.

Does the test lamp flash while the engine is being cranked?

--

Go to Step 10

Go to Step 11

9

Test the spark plug wires for the following conditions:

    • Proper routing and correct firing order--Refer to Ignition System Specifications .
    • Arching to ground

       Important: If carbon tracking or corrosion is detected, replace both components that are affected.

    • Carbon tracking or corrosion

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

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 16

Go to Step 14

11

Test for an intermittent and for a poor connection at the ICM. 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 16

Go to Step 15

12

Replace the spark plugs. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 16

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13

Replace the spark plug wires. Refer to Spark Plug Wire Replacement .

Did you complete the replacement?

--

Go to Step 16

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14

Replace the ignition coil. Refer to Ignition Coil Replacement .

Did you complete the replacement?

--

Go to Step 16

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15

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 16

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16
  1. Turn the ignition OFF for 30 seconds.
  2. Start the engine and operate the vehicle.
  3. Observe the vehicle performance and driveability.

Does the vehicle operate normally?

--

System OK

Go to Step 3