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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 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) consists of the following circuits:

    • The ignition control (IC) timing signal
    • The IC timing control
    • The low resolution engine speed signal
    • The medium resolution engine signal
    • The camshaft position signal
    • The low reference

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

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

The ICM monitors the CKP sync signal when the engine is cranking. The CKP sync signal is passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The CKP sync signal is used to determine the correct cylinder pair and initiate the ignition coil firing sequence. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 circuit. The 18X reference pulses are used for fuel injection and ignition control. After the ICM receives both signals, the ICM passes the 18X and 3X reference signals to the PCM. The CMP and the CKP sensors share a 12 volt reference and low reference circuit. The CKP sensor consists of the following circuits:

    • A 12 volt reference
    • A low reference
    • A CKP sensor 1 signal
    • A CKP sensor 2 signal

Diagnostic Aids

If the camshaft position signal is not present at start-up, the PCM will begin sequential fuel delivery with a 1 in 6 chance that fuel delivery is correct.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following items:

    • Poor connection or damaged harness. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
    • Faulty engine coolant temperature (ECT) sensor. Using a scan tool, compare ECT with intake air temperature (IAT) on a completely cool engine. ECT should be within 10°C (50°F) of IAT. If not, replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Test Description

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

  1. Determines if the (IC) module is receiving the CKP sensor 1 signal. If the CKP sensor 1 signal to the ICM is not present, there will be no RPM, spark, or fuel injector pulses.

    2.

  2. Ensures that the IC module has the proper voltage supply and ground.

    3.

  3. Verifies that the IC module is supplying the 10 volt reference to the sensor.

    4.

  4. Check for the proper operation of the CKP sensor 2 signal, IC module and related spark system components. Without the CKP sensor 2 signal the IC module is unable to properly sequence the ignition coils.

    5.

  5. If the CKP sensor 1 signal and CKP sensor 2 signals to the PCM or the medium resolution and low resolution engine speed signals to the IC module short together the vehicle will not start and run. However, there will be spark and fuel injector pulses.

Electronic Ignition (EI) Diagnosis

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls ?

--

Go to Step  2

Go to Diagnostic System Check - Engine Controls

2

Important: Before proceeding with this diagnostic table, verify that the vehicle's battery is fully charged.

Important: If any ignition DTCs are stored as Failed Since Code Clear, diagnose those DTCs before continuing with this diagnosis.

  1. Check the fuses which supply ignition 1 voltage to the following components:
    2. • The ignition control module (ICM)
    • The powertrain control module (PCM)
  2. If either fuse is open, locate and repair the short to ground in the affected circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step  3

3

  1. Connect a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the Engine Data 1 display on the scan tool.
  4. Observe the engine RPM while cranking the engine.

Does the scan tool indicate an engine RPM?

--

Go to Step 15

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the ICM connector.
  3. Turn ON the ignition.
  4. Connect a test lamp between the ignition positive feed terminal and the ground terminal in the ICM connector.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 5

5
  1. Leave the ICM connector disconnected.
  2. Connect the test lamp between the ICM ignition 1 voltage and the engine ground.

Does the test lamp illuminate?

--

Go to Step 28

Go to Step 29

6

  1. Turn OFF the ignition.
  2. Reconnect the ICM connector.
  3. Disconnect the crankshaft position (CKP) sensor.
  4. Turn ON the ignition .
  5. Connect a DMM between the 10 volt reference terminal and the ground terminal in the CKP sensor connector.

Does the voltage measure near the specified value?

B+

Go to Step 7

Go to Step 9

7

Connect the DMM between the CKP sensor 1 signal terminal and the ground terminal in the connector.

Does the voltage measure within the specified range?

6-8 V

Go to Step 8

Go to Step 12

8
  1. Check for faulty terminal connections at the CKP sensor.
  2. Repair any connections if necessary. Refer to the following procedures in Wiring Systems:

Did you find and correct the condition?

--

Go to Step 33

Go to Step 31

9

Connect the DMM between the CKP 10 volt reference circuit and engine ground.

Does the voltage measure near the specified value?

B+

Go to Step 10

Go to Step 11

10
  1. Turn OFF the ignition.
  2. Leave the CKP sensor disconnected.
  3. Disconnect the ICM connector.
  4. Test the CKP sensor ground for an open.
  5. Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 27

11
  1. Turn OFF the ignition.
  2. Leave the CKP sensor disconnected.
  3. Disconnect the ICM connector.
  4. Test the CKP 10-volt reference circuit for an open and for a short to ground.
  5. Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 27

12
  1. Leave the DMM connected.
  2. Turn OFF the ignition.
  3. Disconnect the ICM connector.
  4. Turn ON the ignition.

Does the voltage measure near the specified value?

B+

Go to Step 13

Go to Step 14

13

Locate and repair the short to voltage in the CKP sensor 1 signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 33

--

14
  1. Test the CKP sensor 1 signal circuit for the following conditions:
    2. • An open
    • A short to ground or a short to sensor ground
  2. Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 27

15

  1. Turn OFF the ignition.
  2. Disconnect a spark plug wire from a spark plug.
  3. Install J 26792 spark tester in the end of the spark plug wire.
  4. Jump the companion cylinder's ignition wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil .
  5. Crank the engine while observing the J 26792 . A spark should be observed.
  6. Repeat the above test for each ignition wire, noting any cylinders that do not have spark.

Do all of the cylinders have spark?

--

Go to Step 25

Go to Step 16

16

Do any of the cylinders have spark?

--

Go to Step 21

Go to Step 17

17
  1. Turn OFF the ignition.
  2. Disconnect the CKP sensor connector.
  3. Turn ON the ignition.
  4. Connect the DMM between the CKP sensor 2 signal circuit and ground.

Does the voltage measure within the specified range?

6-8 V

Go to Step 18

Go to Step 19

18
  1. Test for faulty terminal connections at the CKP sensor.
  2. Repair any terminals as necessary. Refer to the following procedures in Wiring Systems:

Did you find and correct the condition?

--

Go to Step 33

Go to Step 30

19
  1. Turn OFF the ignition.
  2. Disconnect the ICM connector.
  3. Turn ON the ignition.
  4. Test the CKP sensor 2 signal circuit for a short to voltage or a short to the sensor 10 volt reference circuit.
  5. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 20

20
  1. Test for the following conditions:
    2. • The CKP sensor 2 signal circuit for a short to ground and for a short to sensor ground.
    • An open CKP sensor 2 signal circuit.
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 27

21

Important:: If carbon tracking is detected on any component, replace that component and the mate.

  1. Inspect the ignition coils and the ignition wires associated with the cylinders that did not have spark. Verify that the ignition components are free of cracks and carbon tracking.
  2. Replace any damaged ignition components. Refer to Ignition Coil Replacement .

    3. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Step 22

22
  1. Measure the secondary resistance of the ignition coils .
  2. If any ignition coil's resistance is outside the specified range, replace the coil. Refer to Ignition Coil Replacement .

Did you find and correct the condition?

5000-8000 ohms

Go to Step 33

Go to Step 23

23
  1. Measure the resistance of the ignition wires associated with the cylinders that did not have spark. Refer to Spark Plug Wire Inspection .
  2. Replace the ignition wires that have a resistance of more than the specified value. Refer to Spark Plug Wire Replacement .

Did you find and correct the condition?

3000 ohms/ft

Go to Step 33

Go to Step 24

24
  1. Remove the coils associated with the cylinder that did not have spark.
  2. Connect a test lamp across the ignition module primary circuit, between the ICM terminals, for the coils. Refer to Troubleshooting with a Test Lamp in Wiring Systems.
  3. Observe the test lamp while cranking the engine.

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

--

Go to Step 32

Go to Step 31

25
  1. Remove the spark plugs from all of the cylinders.
  2. Inspect the spark plug electrodes.

Are any of the spark plugs fouled?

--

Go to Engine Compression Test in Engine Mechanical

Go to Step 26

26

Refer to Diagnostic Aids to check for the following conditions:

    • A short between the CKP sensor 1 and CKP sensor 2 signal inputs to the ICM.
    • A short between the medium resolution and low resolution engine speed signal inputs to the PCM.
    • If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 33

Go to Engine Compression Test in Engine Mechanical

27
  1. Check for faulty terminal connections at the ICM.
  2. Repair any terminals as necessary . Refer to the following procedures in Wiring Systems:

Did you find and correct the condition?

--

Go to Step 33

Go to Step 31

28

Locate and repair an open in the ICM ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 33

--

29

Locate and repair an open in the ignition 1 voltage circuit to the ICM. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 33

--

30

Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 33

--

31

Replace the ignition control module. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 33

--

32

Replace the ignition coils associated with the cylinders that did not have spark. Refer to Ignition Coil Replacement .

Did you complete the replacement?

--

Go to Step 33

--

33
  1. Remove all of the test equipment.
  2. Connect any disconnected components.
  3. Turn the ignition OFF for 30 seconds.
  4. Start the engine and operate vehicle.
  5. Observe the MIL, and note the vehicle performance and driveability.

Does the vehicle operate normally, with no MIL and no stored DTCs?

--

System OK

Go to Step 1