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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 G5 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

Each ignition coil/module has the following circuits:

    • An ignition voltage circuit
    • A ground
    • An ignition control (IC) circuit
    • A low reference circuit

The powertrain control module (PCM) controls the individual coils by transmitting timing pulses on the IC circuit of each ignition coil/module to enable a spark event.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plug electrode is tipped with platinum for long wear and higher efficiency.

Diagnostic Aids

Perform the spark plug inspection procedure before continuing with this diagnostic. Refer to Spark Plug Inspection .

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 - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Inspect the fuse that supplies ignition voltage to the ignition coil/modules.

Is the fuse open?

--

Go to Step 9

Go to Step 3

3
  1. Disconnect the harness connector of the affected ignition coil/module.
  2. Test for an intermittent and for a poor connection at the ignition coil/module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 4

4
  1. Turn ON the ignition, with the engine OFF.
  2. Measure the battery voltage with a DMM.
  3. Connect a test lamp from the ignition voltage circuit of the affected ignition coil/module to a good ground.
  4. With the test lamp connected, measure the voltage from the ignition voltage circuit to a good ground with a DMM.

Does the voltage measure within 0.5 volt of the specified value?

B+

Go to Step 5

Go to Step 10

5
  1. Turn OFF the ignition, and all electrical accessories and components.
  2. Allow sufficient time for the control modules to power down before taking a resistance measurement.
  3. Measure the resistance of the ground circuit of the affected ignition coil/module from the harness connector of the ignition coil/module to a good ground with a DMM.

Is the resistance less than the specified value?

3 ohms

Go to Step 6

Go to Step 11

6
  1. Exchange the affected ignition coil/module with one from a cylinder that is not misfiring.
  2. Start the engine.
  3. Observe the Misfire Data List with a scan tool.

Does the misfire follow the transferred ignition coil/module?

--

Go to Step 12

Go to Step 7

7

Test the ignition control (IC) circuit of the affected ignition coil/module for the following conditions:

    • A high resistance or an open
    • A short to ground
    • A short to voltage

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 8

8

Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

9

Repair the short to ground in the spliced circuits or the ignition coil/module, as needed. Refer to Testing for Short to Ground and Wiring Repairs .

Did you complete the repair?

--

Go to Step 14

--

10

Repair the high resistance or an open in the ignition voltage circuit of the affected ignition coil/module. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 14

--

11

Repair the high resistance or an open in the ground circuit of the affected ignition coil/module. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 14

--

12

Replace the ignition coil/module. Refer to Ignition Coil Replacement .

Did you complete the replacement?

--

Go to Step 14

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13

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 14

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14
  1. Turn the ignition OFF for 60 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 2