GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Engine Cranks But Does Not Run

Refer to Engine Controls Schematics for a wiring view.

Circuit Description

The electronic ignition system uses a waste spark method of spark distribution. In this type of ignition system, the ignition control module triggers the correct coil based on the sync signal received from the crankshaft position sensor, resulting in both spark plugs connected to the coil firing at the same time. The spark plug for the cylinder on the exhaust stroke requires a lower energy requirement in order to fire, leaving the remaining high voltage to fire the spark plug for the cylinder on the compression stroke.

During crank, the ignition control module monitors the crankshaft position (CKP) sync signal. The CKP sync signal is used to determine the correct cylinder pair to fire first. The CKP sync signal is used only by the ignition control module in order to initiate the ignition coil firing sequence. It is not passed to the PCM. After the ignition control module processes the CKP sync signal, the ignition control module monitors the 18X CKP signal and sends 18X and 3X reference pulses to the PCM. When the PCM receives these pulses, the PCM will command all six injectors in order to allow a priming shot of fuel for all the cylinders. After the priming, the injectors are left OFF during the next six 3X reference pulses from the ignition control module. This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, the PCM receives a camshaft position signal pulse. The camshaft position signal allows the PCM to operate the injectors sequentially, based on camshaft position. 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.

Diagnostic Aids

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:

    • A shorted camshaft position sensor
        An internally-shorted camshaft position sensor can cause an Engine Cranks but Will not Run condition. If the diagnostic table indicates a short to ground in the sensor ignition positive voltage circuit, disconnect the camshaft position sensor and attempt to start the vehicle. If the vehicle starts with the camshaft position sensor disconnected, a shorted camshaft position sensor is indicated.
    • A poor connection or a damaged harness
        Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connections, and a damaged harness.
    • A malfunctioning engine coolant temperature sensor
        Using a scan tool, compare the engine coolant temperature with the intake air temperature on a completely cool engine. The engine coolant temperature should be within 10°C (50°F) of the intake air temperature. If it is not, replace the ECT sensor.
    • The throttle position (TP) sensor
        If the TP angle is more than 80 percent, the PCM may operate in clear flood mode. The PCM will not allow fuel delivery while operating in clear flood mode.

Test Description

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

  1. This step determines if the ignition control module (ICM) is receiving the 18X crankshaft position (CKP) Reference signal. If the 18X CKP signal to the ICM is not present, there will be no RPM, no spark, and no fuel injector pulses.

    2.

  2. This step ensures that the ICM has the proper voltage supply and ground.

    3.

  3. This step verifies that the ignition control module (ICM) is supplying the proper sensor feed voltage.

    4.

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

    5.

  5. If the 18X and CKP Sync signals to the ICM or the 18X and 3X reference signals to the ICM short together, the vehicle will not start and run. However, there will be spark and fuel injector pulses.

    6.

  6. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Engine Cranks But Will Not Run

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Important: If the engine cranks and does not run, test the ignition relay feed circuits to and from the ignition relay. Refer to Power Distribution Schematics and Circuit Testing in Wiring Systems.

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

Important: If any DTCs are stored as Failed since code clear (except for P1374, P0336, or P0341), diagnose the DTCs before continuing with this table.

  1. Check the fuses which supply the ignition positive voltage to the following components:
    2. • The electronic ignition control module.
    • The fuel injectors.
  2. If either fuse is blown, locate and repair the short to ground in the affected ignition positive voltage circuit.

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 3

3

With a scan tool, command the fuel pump ON.

Does the fuel pump turn ON?

--

Go to Step 4

Go to

Fuel Pump Electrical Circuit Diagnosis

4
  1. Turn OFF the ignition.

    2. Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

  2. Install a fuel pressure gauge J 34730-1A at the fitting on the fuel rail.
  3. Turn the ignition switch to the ON position.
  4. Observe the fuel pressure gauge.

Is the fuel pressure within the specified values and holding?

333-376 kPa (48-55 psi)

Go to Step 5

Go to

Fuel System Pressure Test (VIN K)

5

  1. Turn OFF the ignition.

    2. Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete.

  2. Remove the fuel pressure gauge from the fuel rail.
  3. Install the scan tool.
  4. Turn the ignition switch to the ON position.
  5. Select the Engine Data 1 display on the scan tool.
  6. Observe the engine RPM while cranking the engine.

Does the scan tool indicate an engine RPM?

--

Go to Step 17

Go to Step 6

6

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the ignition control module (ICM) connector.
  3. Turn the ignition switch to the ON position.
  4. Connect J 35616-200 test lamp between the ignition positive feed and ground terminals in the ICM connector.

Is the test lamp ON?

--

Go to Step 8

Go to Step 7

7
  1. Leave the ICM connector disconnected.
  2. Connect the J 35616-200 test lamp between the ignition positive feed and engine ground.

Is the test lamp ON?

--

Go to Step 39

Go to Step 40

8

  1. Turn the ignition switch to the OFF position.
  2. Reconnect the ICM connector.
  3. Disconnect the 18X crankshaft position (CKP) sensor connector.
  4. Turn the ignition switch to the ON position.
  5. Connect Digital Multimeter (DMM) between the 18X CKP sensor feed and the sensor ground terminals in the connector.

Does the DMM display a voltage near the specified value?

B+

Go to Step 9

Go to Step 11

9

Connect the DMM between the 18X CKP sensor signal and the sensor ground terminals in the connector.

Does the DMM display a voltage near the specified values?

6-8V

Go to Step 10

Go to Step 14

10
  1. Check for poor terminal connections at the 18X CKP sensor.
  2. If you find a problem, repair the condition as necessary. Refer to Testing for Continuity , Testing for Intermittent Conditions and Poor Connections , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 41

11

Connect the DMM between the 18X CKP sensor feed and the engine ground.

Does the DMM display a voltage near the specified value?

B+

Go to Step 12

Go to Step 13

12
  1. Turn the ignition switch to the OFF position.
  2. Leave the 18X CKP sensor connector disconnected.
  3. Disconnect the ICM connector.
  4. Check the 18X CKP sensor ground for an open.
  5. If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

13
  1. Turn the ignition switch to the OFF position.
  2. Leave the 18X CKP sensor connector disconnected.
  3. Disconnect the ignition ICM connector.
  4. Check the 18X CKP sensor feed for an open or a short to ground.
  5. If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

14
  1. Leave the DMM connected.
  2. Verify that the ignition is ON.

Does the DMM display a voltage near the specified value?

B+

Go to Step 15

Go to Step 16

15
  1. Locate and repair the short between the 18X CKP sensor signal circuit and the following circuits:
    2. • The 18X CKP sensor feed circuit
    • The battery positive voltage
  2. If a problem is found, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

16
  1. Turn the ignition switch to the OFF position.
  2. Check the 18X CKP signal circuit for the following conditions:
    3. • An open
    • A short to ground
  3. If a problem is found, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

17
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the fuel injector connectors.
  3. Turn the ignition switch to the ON position.
  4. Observe the J 34730-405 fuel injector test lamp when it is installed in each injector connector.

Was the injector test lamp ON for any of the injectors?

--

Go to Step 18

Go to Step 19

18
  1. Leave the fuel injector connectors disconnected.
  2. Turn the ignition switch to the OFF position.
  3. Disconnect the PCM connector.
  4. Turn the ignition switch to the ON position.
  5. Observe J 34730-405 the injector test lamp in the injector connectors.

Was the test lamp ON for any of the injectors?

--

Go to Step 43

Go to Step 46

19
  1. Leave the fuel injector connectors disconnected.
  2. Leave the J 34730-405 injector test lamp installed in the injector connector.
  3. Observe the J 34730-405 injector test lamp while cranking the engine. Repeat this step for each injector.

Did the injector test lamp blink for each injector?

--

Go to Step 24

Go to Step 20

20

Did the J 34730-405 injector test lamp blink for any of the injectors?

--

Go to Step 21

Go to Step 22

21
  1. Turn the ignition switch to the OFF position.
  2. Leave the injector connectors disconnected.
  3. Disconnect the PCM connector.
  4. Check for an open in the fuel injector control circuits associated with the J 34730-405 injector test lamp that did not blink.
  5. If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 44

22
  1. Leave the fuel injector connectors disconnected.
  2. Turn ON the ignition.
  3. Connect a J 35616-200 test lamp to a ground.
  4. Probe the ignition positive voltage feed circuit to each injector connector.

Is the test lamp ON?

--

Go to Step 44

Go to Step 23

23

Locate and repair the open ignition positive feed circuit to the fuel injectors. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

24

  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. Jumper the companion cylinder ignition wire to the engine ground. The companion cylinder is the cylinder that shares the same ignition coil , for example, 1/4, 2/5, or 3/6.
  5. Crank the engine while observing the J 26792 spark tester. You should see spark.
  6. Repeat the above test for each ignition wire, noting any cylinders that do not have spark.

Is spark available at all the cylinders?

--

Go to Step 34

Go to Step 25

25

Is spark available at any cylinder?

--

Go to Step 30

Go to Step 26

26
  1. Turn OFF the ignition.
  2. Disconnect the 18X CKP sensor connector.
  3. Turn ON the ignition.
  4. Connect the DMM between the CKP Sync signal circuit and a ground.

Does the DMM display a voltage near the specified value?

6-8V

Go to Step 27

Go to Step 28

27
  1. Check for poor terminal connections at the 18X CKP sensor.
  2. If you find a problem, repair the condition as necessary. Refer to:
    3. •  and
    • in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 41

28
  1. Turn OFF the ignition.
  2. Disconnect the ICM connector.
  3. Turn ON the ignition.
  4. Check the CKP Sync signal circuit for a short to voltage or to the 18X CKP sensor ignition feed circuit.
  5. If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 29

29
  1. Turn OFF the ignition.
  2. Check for the following circuit conditions:
    3. • The CKP Sync signal circuit for a short to ground or to any sensor ground wire.
    • An open CKP Sync signal circuit.
  3. If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 38

30

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

  1. Visually and physically inspect the ignition coils and the ignition wires associated with the cylinders that did not have spark. Ensure that the ignition wires, boots, coils, and coil towers are free of cracks and carbon tracking.
  2. If you find a problem, replace the damaged ignition components. Refer to:
    3. • and

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 31

31
  1. Measure the ignition coil secondary resistance.
  2. If any resistance is outside the specified values, replace the malfunctioning ignition coils as necessary. Refer to Ignition Coil Replacement .

Did you find a problem?

5K-8K ohms (5000 - 8000 ohms)

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 32

32
  1. Measure the resistance of the ignition wires associated with the cylinders that did not have spark.
  2. Replace the ignition wires that measure greater than the specified value. Refer to Spark Plug Wire Harness Replacement .

Did you find a problem?

3280 - 4921 ohms per meter (1000 - 1500 ohms per ft.)

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 33

33
  1. Remove the coils associated with the cylinders that did not have spark.
  2. Connect a J 35616-200 test lamp across the ignition module primary circuit, between the electronic ignition control module terminals, for the coils associated with the cylinders which did not have spark. Refer to Ignition Coil Replacement .
  3. Observe the test lamp while cranking the engine.

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

--

Go to Step 45

Go to Step 42

34
  1. Remove the spark plugs from all the cylinders.
  2. Visually and physically inspect the spark plug electrodes.

Did the spark plug inspection reveal excessive fouling?

--

Go to Base Engine Misfire Diagnosis

Go to Step 35

35

Refer to Diagnostic Aids to check for the following conditions:

    • A short between the 18X CKP and CKP Sync signal inputs to the ICM.
    • A short between the 18X and 3X reference signal inputs to the PCM.
    • A stuck TP sensor.
    • A skewed ECT sensor.
    • A skewed or unresponsive MAP sensor.
    • A faulty MAF Sensor
    • A faulty IAC Valve

If you found a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 36

36
  1. Test the fuel for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
  2. If you find a problem, clean the fuel system and correct the contaminated fuel conditions as necessary.

Did you find a problem found

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 37

37

Inspect for the following conditions. Refer to Engine Compression Test .

    • Bent push rods
    • A leaking head gasket
    • A malfunctioning or incorrect camshaft
    • Leaking or sticky valves or rings
    • Excessive valve deposits
    • Loose or worn rocker arms
    • Weak valve springs
    • Incorrect valve timing

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

38
  1. Check for poor terminal connections at the ICM.
  2. If a problem is found, repair the condition as necessary. Refer to:
    3. • and

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 42

39

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

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

40

Locate and repair the open in the ignition positive feed circuit to the ICM. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

41

Replace the 18X CKP sensor. Refer to Crankshaft Position Sensor Replacement .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

42

Replace the ICM.

Refer to Ignition Control Module Replacement .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

43

Locate and repair the short to ground in the fuel injector control circuits associated with the injector J 34730-405 test lamps that stayed ON. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

44
  1. Check for poor terminal connections at the PCM. Refer to:
  2. If you find a problem, repair the condition as necessary.
    3. • and

Did you find a problem?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 46

45

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

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--

46

Important: The replacement PCM must be reprogrammed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

--