GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Canyon Pickup - 2WD 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

The ignition system uses individual ignition coil/module assemblies for each cylinder. The powertrain control module (PCM) controls the individual coils by transmitting timing pulses on the ignition control (IC) circuit of each ignition coil/module to enable a spark event. The PCM monitors each IC circuit for improper voltage levels. Each ignition coil/module has the following circuits:

    • An ignition voltage circuit
    • A ground
    • An IC 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 - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Remove the fuel pump relay.
  3. Test for spark at each cylinder with a J 26792 Spark Tester.

Did you have spark on all cylinders?

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Go to Step 3

Go to Step 5

3

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

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Go to Step 4

Go to Step 9

4
  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

5
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the ignition coil/module for the affected cylinder.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp from the ignition voltage circuit to the ground circuit of the ignition coil/module.

Does the test lamp illuminate?

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Go to Step 7

Go to Step 6

6

Connect a test lamp from the ignition voltage circuit of the ignition coil/module to a good ground.

Does the test lamp illuminate?

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Go to Step 11

Go to Step 10

7
  1. Turn OFF the ignition.
  2. Remove the fuse that supplies ignition voltage to the ignition coil/module.
  3. Measure the resistance of ignition voltage circuit of the ignition coil/module from the fuse to the harness connector of the ignition coil/module with a DMM.

Is the resistance less than the specified value?

3 ohms

Go to Step 8

Go to Step 10

8

Measure the resistance of ground circuit of the ignition coil/module from the harness connector of the ignition coil assembly to a good ground with a DMM.

Is the resistance less than the specified value?

3 ohms

Go to Step 9

Go to Step 11

9

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 13

10

Repair the ignition voltage circuit of the ignition coil/module for one of the following conditions:

    • An open
    • A short to ground
    • High resistance

Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 14

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11

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

Did you complete the repair?

--

Go to Step 14

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12

Replace the spark plugs. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 14

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13

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

Did you complete the replacement?

--

Go to Step 14

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14
  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 2