Engine Cranks But Does Not Run. Buick Century 1999

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Engine Cranks But Does Not Run

Engine Controls Components
Cell 20: Ignition System and Knock Sensor
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

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 3X 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 to fire, leaving the remaining high voltage to fire the spark plug for the cylinder on the compression stroke.

During cranking, the ignition control module monitors the crankshaft position sensor input for recognition of the sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal has been processed by the ignition control module, it sends a 3X reference signal to the PCM. When the PCM receives this signal it will command all six injectors to open for one priming shot of fuel in all cylinders. After the priming, the injectors are left OFF for the next six 3X reference signals from the ignition control module (two crankshaft revolutions). This allows each cylinder to use the fuel from the priming shot. During this waiting period, a cam signal will have been received by the PCM. After the true camshaft position is detected, the PCM operates the injectors sequentially. However, if the cam signal is not present at start-up, DTC P0341 Camshaft Position (CMP) Sensor Performance will set and the PCM will start sequential fuel delivery in random pattern with a 1 in 6 chance that fuel delivery is correct.

The sync signal is used only by the ignition control module. It is used for spark synchronization at start-up only (not passed to the PCM).

Diagnostic Aids

Inspect for the following items:

•	Mass Air Flow is compared to a calculated Mass Air Flow based upon the MAP, TP, and engine RPM readings (speed density). A Skewed/unresponsive MAP sensor at KEY ON will cause the predicted air flow value to be inaccurate. Compare MAP and TP sensor to that of a normal operating system.

•

Faulty Engine Coolant Temperature Sensor. Using a scan tool, compare Engine Coolant Temperature with Intake Air Temperature on a completely cool engine. Engine Coolant Temperature should be within 10°C of Intake Air Temperature. If not, replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

•	Poor terminal connection.

Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Intermittents and Poor Connections Diagnosis , and Connector Repairs Wiring Systems.

•	Damaged harness.

Inspect the wiring harness for damage. If the harness appears to be OK, observe the sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the sensor display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems.

•	Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Fail Records can be useful in determining when the DTC was last set.

Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table:

A skewed MAP sensor can cause the BARO reading to be incorrectly calculated. To test the MAP sensor, compare the MAP/BARO reading on the vehicle to the MAP/BARO reading on a normally operating vehicle. If there is a skewed or stuck map sensor vehicle may not start, compare the MAP reading with that of another vehicle.

This step checks the MAP sensor. By disconnecting the MAF sensor, the vehicle is forced into speed density; Speed density is based on the MAP, TP, and engine RPM readings. With a skewed/unresponsive MAP sensor, the speed density calculation is incorrect and vehicle may not start.

A blinking J 34730-2C Injector Test Light verifies that the PCM is capable of activating the injectors.

A non-blinking J 34730-2C Injector Test Light indicates a possible fault condition in the fuel injector circuits.

Checking for spark at an ignition wire will determine if the problem is with the 7X crankshaft position sensor input to the IC Module. A blinking injector J 34730-2C Injector Test Light with no spark suggests a fault condition in the ignition system. By using J 26792 Spark Tester to test for spark at the ignition coil towers, each ignition coils ability to produce at least 25,000 volts is verified.

By testing the problem coils control circuit with a J 34730-2C Injector Test Light, a determination can be made as to the problem coil being faulty or the ignition control modules internal driver circuit for the affected coil being the cause of the complaint.

Before replacing the MAP sensor review Diagnostic Aids. Apply vacuum with hand held vacuum pump while monitoring scan tool, MAP reading should increment smoothly with each stroke of vacuum pump. Refer to MAP Sensor Circuit Test for MAP Sensor diagnosis.

Step

Action

Value(s)

Yes

Was the Powertrain OBD System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Select Failed Since Code Clear with the scan tool.

Is DTC P0101, P0123, P0201-P0206, P0601-P0602, P1374, P1626, P1631 stored?

Go to Applicable DTCs

Go to Step 3

Turn the ignition on, and leave the engine off.
With scan tool monitor MAP sensor.

Is the MAP less than specified value?

65 kPa

Go to Step 27

Go to Step 4

Turn the ignition off.
Disconnect the MAP sensor.
Attempt to start the engine.

Does engine start and continue to run?

Go to Step 27

Go to Step 5

Ignition off, reconnect MAP sensor connector.
Install a fuel pressure gage at the fitting on the fuel rail.
Turn the ignition on.
Observe the fuel pressure.

Is the fuel pressure within the specified values and holding?

260-370 kPa (37-53 psi)

Go to Step 7

Go to Step 6

Is any fuel pressure indicated?

Go to Fuel System Pressure Test

Go to Fuel Pump Electrical Circuit Diagnosis

Turn the ignition off.
Disconnect the injector 10-way connector.
Install J 34730-380 injector test light using J 34730-385 adaptor harness in the connector.
Observe injector J 34730-380 test light while cranking the engine.

Does all of the LEDs for cylinders 1-6 flash?

Go to Step 8

Go to Step 9

Remove the fuel injection fuse from the underhood electrical center.
Install a J 26792 spark tester on an ignition wire.
Connect one end of the ignition wire to one coil tower of 2, 4, and 6 (one at a time).
Clip the ST 125 to the coil tower of each companion cylinder. The companion cylinder is the cylinder that shares the same ignition coil (i.e., 1/4, 2/5, 3/6).
Crank the engine while observing the J 26792 spark tester. A spark should be observed.

Is spark provided by the secondary coils?

Go to Step 19

Go to Step 11

Test the fuse for the fuel injector feed circuit.
If the fuse blown, test for the following circuit faults:

•	An open or a short to ground in the fuel injector feed circuit.

•	A shorted injector.

If a problem is found, repair it as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 10

Locate and repair open in the fuel injector feed and driver circuit. Refer to Wiring Repairs .

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 31

Test the fuse for the electronic ignition control module ignition feed circuit.
If the fuse is blown, locate and repair short to ground in ignition control module ignition feed circuit or short to battery positive voltage in the IC circuit. Refer to Wiring Repairs .

Was the fuse blown?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 12

Test for an open in the electronic ignition control module feed and ground circuits.
If a problem is found, repair it as necessary. Refer to Wiring Repairs .

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 13

Turn OFF the ignition.
Disconnect the 2 wire, 7X CKP sensor (PPL and YEL wires) connector from the ICM.
Connect a DMM between the 7X CKP sensor harness connector terminals.
Set the DMM to read ohms.

Is the resistance between the specified value?

800-1,200 ohms

Go to Step 15

Go to Step 14

Turn the ignition off.
Test the 7X CKP circuit for the following conditions:

•	An open circuit.

•	A short to ground.

•	A short to battery positive voltage.

•	7X wiring harness shorted together.

•	Poor connections at 7X crankshaft position sensor

•	If a problem is found, repair it as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , Connector Repairs , and Wiring Repairs .

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 28

Test for poor connections at the IC Module.
If a problem is found, repair it as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs .

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 16

Remove and visually/physically inspect the ignition coil(s) associated with the cylinders that did not have spark. Ensure that the coils and coil towers are free of cracks and carbon tracking.
If a problem is found, replace damaged ignition coil(s) as necessary.

Did the inspection reveal a problem?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 17

Measure the ignition coil secondary resistance.
If any resistance is outside the specified values, replace faulty ignition coil(s) as necessary.

Is the resistance outside the specified values?

5K-7K ohms (5,000-7,000 ohms)

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 18

Connect a J 35616-200 test light across the ignition module primary circuit (between the electronic ignition control module terminals) for coil(s) associated with the cylinders which did not have spark.
Observe the J 35616-200 test light while cranking the engine.

Does the J 35616-200 test light blink while the engine is being cranked?

Go to Step 29

Go to Step 30

Visually/physically inspect the 2, 4, and 6 cylinder ignition wires. Ensure that the wires and boots are free of carbon tracking and the insulation is not damaged.
If a problem is found, replace faulty ignition wire(s) as necessary.

Did the inspection reveal any faulty ignition wires?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 20

Measure the resistance of the 2, 4, and 6 cylinder ignition wires.
If any resistance is outside the specified value, replace the faulty ignition wire.

Was a problem found?

600ohms per foot (1 968ohms per meter)

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 21

Remove the spark plugs from cylinders 2, 4, and 6.
Visually inspect the spark plug electrodes.

Does your inspection reveal any spark plugs exhibiting excessive fouling?

Go to Step 26

Go to Step 22

Visually/physically inspect the 1, 3, and 5 cylinder ignition wires. Ensure that the wires and boots are free of carbon tracking and the insulation is not damaged.
If a problem is found, replace faulty ignition wire(s) as necessary.

Did inspection reveal any faulty ignition wires?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 23

Measure the resistance of the 1, 3, and 5 cylinder ignition wires.
If any resistance is outside the specified value, replace the faulty ignition wire.

Was a problem found?

600ohms per foot (1 968ohms per meter)

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 24

Remove the spark plugs from cylinders 1, 3, and 5.
Visually inspect the spark plug electrodes. Refer to Spark Plug Visual Diagnosis .

Does your inspection reveal any spark plugs exhibiting excessive fouling?

Go to Step 26

Go to Step 25

Test the fuel for contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
If a problem is found, clean the fuel system and correct the contaminated fuel condition as necessary.

Was a problem found?

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Diagnostic Aids

Refer to Engine Mechanical Diagnosis to diagnose the following conditions:

•	Bent push rods

•	Faulty or incorrect camshaft

•	Leaking or sticky valves or rings

•	Excessive valve deposits

•	Loose or worn rocker arms

•	Weak valve springs

•	Incorrect valve timing

•	Leaking head gasket

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check

Replace MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check

Replace the 7X crankshaft position sensor. Refer to Crankshaft Position Sensor Replacement .

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check

Replace the ignition coil(s) associated with the cylinders that did not have spark. Refer to Ignition Coil Replacement Ignition Control Module.

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check

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

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check

Important: : Replacement PCM must be programmed.

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

Is the action complete?

Go to Powertrain On Board Diagnostic (OBD) System Check