GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 CTS - RHD 🢒 Engine 🢒 Engine Electrical 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

This distributorless ignition system consists of two coil packs, a crankshaft position (CKP) sensor, and the engine control module (ECM). The ECM performs all of the ignition control (IC) module functions. The ignition coil assembly has voltage supplied by an ignition feed circuit and also contains a dedicated ground circuit. The remaining three circuits go to the ECM and are the IC circuits. The ECM causes a spark to occur by pulsing an IC circuit, which triggers an ignition coil and fires the appropriate spark plug. The ECM controls the sequencing and the timing internally.

Test Description

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

  1. The spark tester should show steady, consistent spark across the tip of the spark tester when using the scan tool to operate the coil.

    2.

  2. This step tests the diode in the secondary side of the coil and the continuity of the ground circuit inside the coil. You should be able to read continuity in one direction only.

    3.

  3. This step is to verify the operation of the ignition coil control circuit and the driver in the ECM.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector 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

Attempt to start the engine.

Does the engine start and idle?

--

Go to Step 3

Go to Step 14

3
  1. Idle the engine.
  2. Monitor the misfire counters with a scan tool.

Does the misfire counters increment for one complete bank?

--

Go to Step 4

Go to Step 6

4
  1. Turn OFF the ignition.
  2. Disconnect the electrical connector for the affected coil pack .
  3. Probe the ground circuit of the coil pack with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 13

5
  1. Turn ON the ignition.
  2. Probe the ignition voltage circuit of the coil pack with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 14

6

  1. Turn OFF the ignition.
  2. Remove the affected coil pack from the engine. Refer to Ignition Coil Replacement - Bank 1 or Ignition Coil Replacement - Bank 2 .
  3. Leave the electrical connector connected.
  4. Disconnect the fuel injector harness multi-connector.
  5. Install a J 26792 Spark Tester into one coil or the affected coil of the cylinder, if known.
  6. Connect a scan tool.
  7. Turn ON the ignition, with the engine OFF.
  8. Operate the affected ignition coil with a scan tool.
  9. Repeat the above steps for the remaining cylinders.

Does the spark plug tester show spark on all cylinders?

--

Go to Step 19

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the coil pack.
  3. Set a DMM to the diode test function.
  4. Probe the ground circuit of the coil pack with the black test lead, and the inside of the spark plug boot with the red test lead.
  5. Repeat this test on the remaining coils.
  6. Reverse the test leads and repeat the test.

Does the DMM show continuity on the first test and infinite resistance on the second test?

--

Go to Step 8

Go to Step 15

8
  1. Set the DMM set to measure resistance.
  2. Connect one lead of the DMM to the ignition 1 voltage circuit of the coil pack.
  3. Probe the individual ignition control (IC) Circuits at the coil pack with the other lead.

Is the resistance within the specified range?

0.38-0.86 ohms

Go to Step 9

Go to Step 15

9
  1. Turn OFF the ignition.
  2. Disconnect the coil pack electrical connector on the affected coil.

    3. Important: DO NOT substitute a standard test lamp for the injector test lamp. The impedance of the injector test lamp is close to that of the ignition coil. The use of a standard test lamp may produce inaccurate results.

  3. Connect the J 34730-2C TBI Harness Test Lamp between the supply voltage circuit and the control circuit of the affected cylinder with the test adapter leads.
  4. Turn ON the ignition.

Does the injector test lamp illuminate?

--

Go to Step 11

Go to Step 10

10

Enable the coil for the affected cylinder with the scan tool Output Control function.

Does the injector test lamp flash ON and OFF?

--

Go to Step 15

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) electrical connector C1.
  3. Turn ON the ignition .

Is the injector test lamp OFF?

--

Go to Step 17

Go to Step 16

12

    Important: A short to voltage on the coil control circuit may cause damage to the ECM.

  1. Test the affected control circuit for an open or a short to voltage.
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 17

13

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

Did you complete the repair?

--

Go to Step 21

--

14

Repair the open or short to ground in the ignition 1 circuit. Refer to Wiring Repairs in Wiring Systems.

Replace the fuse if the ignition 1 voltage circuit is shorted to ground.

Did you complete the repair?

--

Go to Step 21

--

15

Replace the coil pack. Refer to Ignition Coil Replacement - Bank 1 or Ignition Coil Replacement - Bank 2 .

Did you complete the replacement?

--

Go to Step 21

--

16

Important: A short to ground on a coil control circuit may damage the ignition coil.

Repair the short to ground in the control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

17
  1. Inspect for a faulty connection or a faulty terminal tension at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

18

Important: Perform the idle learn procedure when replacing the ECM or the throttle body.

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 21

--

19

Inspect the system for multiple conditions that may be related to a misfire. For example:

    • Fouled spark plugs caused by the fuel system compensating for a misfiring cylinder
    • Water intrusion or contamination around the coil pack
    • Secondary ignition leakage around the base, tower and the boot of the coil

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

20
  1. Inspect the spark plugs for the proper gap or for signs of damage. Refer to Spark Plug Inspection .
  2. Replace the spark plugs, as necessary. Refer to Spark Plug Replacement .

Did you complete the replacement?

--

Go to Step 21

--

21
  1. Start and idle the engine.
  2. Monitor the misfire counters with the scan tool.

Do any of the misfire counters increment?

--

Go to Step 2

Go to Step 22

22

With a scan tool observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK