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Home >> Cadillac >> 2004 >> CTS Base, 3.6 7 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Controls - 2.6L & 3.2L - Troubleshooting & Diagnosis) >> Troubleshooting >> Electronic Ignition (EI) System Diagnosis >> Circuit Description

Circuit Description

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The Ignition System uses a ignition coil assembly for each bank. Each ignition coil assembly consist of 3 ignition coils. The ignition coil assemblies consist of the following circuits:

The ignition coil assemblies are mounted in the center of each camshaft cover with short boots connecting the coils to the spark plugs. The engine control module (ECM) primarily uses engine speed and position information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor to control the sequence, dwell, and timing of the spark. The ECM can command each ignition coil ON/OFF by grounding the IC circuit of the ignition coil. The IC circuits are pulse width modulated (PWM) in order to precisely control the spark events.

Electronic Ignition (EI) System Diagnosis

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) 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 Attempt to start the engine.
Does the engine start and idle?		 - Go to Step 3  Go to Step 6 
3
  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?		 - Go to Step 4  Go to Step 10 
4 Does the spark tester indicate a bright blue spark on all cylinders? - Go to Step 5  Go to Step 15 
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 21 
6
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the inoperative ignition coil assembly.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp from the ignition voltage circuit of the ignition coil assembly to a good ground.
Does the test lamp illuminate?		 - Go to Step 7  Go to Step 17 
7 Connect a test lamp from the ignition voltage circuit to the ground circuit of the ignition coil assembly.
Does the test lamp illuminate?		 - Go to Step 8  Go to Step 18 
8
  1. Turn OFF the ignition.
  2. Remove the IGN MOD fuse in the underhood fuse block.
  3. Measure the resistance of ignition voltage circuit of the ignition coil assembly from the IGN MOD fuse in the underhood fuse block to the harness connector of the ignition coil assembly with a DMM.
Is the resistance less than the specified value?		 3 Ω Go to Step 9  Go to Step 19 
9 Measure the resistance of ground circuit of the ignition coil assembly 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 Ω Go to Step 15  Go to Step 20 
10
  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the ignition coil assembly.
    3. IMPORTANT: If using a different test lamp, the bulb resistance needs to be 4 ohms or less.
  3. Using jumper wires, connect the J 34730-405  TBI Harness Test Lamp from the ignition voltage circuit of the ignition coil assembly to the IC circuit of the inoperative ignition coil in the harness connector of the ignition coil assembly
  4. Turn ON the ignition, with the engine OFF.
  5. Command the inoperative ignition coil ON with a scan tool.
Does the test lamp flash?		 - Go to Step 12  Go to Step 11 
11 Does the test lamp remain ON? - Go to Step 13  Go to Step 14 
12
  1. Using jumper wires, connect the J 34730-405  from the ignition voltage circuit of the ignition coil assembly to the IC circuit of a known good ignition coil in the harness connector of the ignition coil assembly.
  2. Command the ignition coil ON with a scan tool.
  3. Compare the illumination of the good coil to that of the inoperative coil.
Does the test lamp illuminate with same brightness for both circuits?		 - Go to Step 15  Go to Step 14 
13 Test the IC circuit of the inoperative ignition coil for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 24  Go to Step 16 
14 Test the IC circuit of the inoperative ignition coil for one of the following conditions:
  • An open
  • A short to voltage
  • High resistance of more than 3 ohms

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 24  Go to Step 16 
15 Test for shorted terminals or a poor connection at the ignition coil assembly. 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 24  Go to Step 22 
16 Test for shorted terminals or 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 24  Go to Step 23 
17 Repair an open or a short to ground in the ignition voltage circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 24  -
18 Repair an open in the ground circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 24  -
19 Repair the high resistance in the ignition voltage circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 24  -
20 Repair the high resistance in the ground circuit of the ignition coil assembly. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 24  -
21 Replace the spark plugs. Refer to Spark Plug Replacement .
Did you complete the replacement?		 - Go to Step 24  -
22 Replace the ignition coil assembly. Refer to Ignition Coil(s) Replacement - Bank 1 or Ignition Coil(s) Replacement - Bank 2 .
Did you complete the replacement?		 - Go to Step 24  -
23 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 24  -
24
  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 
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