Electronic Ignition (EI) System Diagnosis. Buick Century 2001

For 1990-2009 cars only

Makes 🢒 Buick 🢒 2001 🢒 Century 🢒 Engine 🢒 Engine Electrical 🢒 Electronic Ignition (EI) System Diagnosis

Circuit Description

The ignition control (IC) module has independent power and ground circuits. The circuits between the IC module and the powertrain control module (PCM) consist of the following circuits:

•	The IC timing signal

•	The IC timing control

•	The low-resolution engine speed signal

•	A low reference signal

The ignition control (IC) module sends 3x signals to the powertrain control module (PCM). The IC module controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions:

•	The PCM receives the second 3x signal.

•	The PCM applies 5 volts to the IC timing signal circuit.

•	The timing advance switches to PCM control.

Test Description

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

It is necessary to disconnect the 24X crank sensor to ensure that the 7X signal is being read in the 3X reference parameter on the scan tool.

The spark tester presents a more difficult load on the secondary ignition than a normal spark plug. If a miss, stumble, or hesitation is being caused by a spark plug not firing, the spark tester should also not fire.

Use a 5 percent saltwater solution in a spray bottle to induce voltage arching to ground through faulty insulation of spark plug wires.

If the no spark condition follows the suspected coil, that coil is faulty. Otherwise, the ignition module is the cause of no spark. This test could also be performed by substituting a known good coil for the one causing the no spark condition.

Step

Action

Values

Yes

Schematic Reference:

Igniton Controls

Master Electrical Component List
Electronic Ignition (EI) System Description
Fuel Injectors
IAC Control
OBD II Symbol Description Notice
Engine Controls Schematic Icons
ATX,ICM,O2
G100,G111 and G113

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Observe the Freeze Frame and Failure records data for the DTC.
Turn OFF ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for running the DTC as specified in the supporting text, or as close to the Freeze Frame and/or Failure records data that you observed.

Does the DTC fail this ignition?

Go to Step 3

Go to Intermittent Conditions

Disconnect the 24X crank sensor.
With a scan tool, observe the 3X crank sensor parameter while cranking the engine.

Does the scan tool indicate 3X crank sensor signal present?

Go to Step 4

Go to Step 11

Reconnect the 24X crank sensor.
With a spark tester, test for spark at each cylinder.

Did you observe any non-sparking cylinders?

Go to Step 5

Go to Step 8

Inspect and test the affected cylinder spark plug wires, ignition coils, and spark plugs for a short to ground or arching to ground. If carbon tracking or corrosion is present, replace both components affected. Refer to Spark Plug Wire Replacement , Ignition Coil Replacement , Spark Plug Replacement .

Did you find and correct the condition?

Go to Step 23

Go to Step 6

Test affected spark plug wires for proper resistance.
Replace spark plug wires not near specification. Refer to Spark Plug Wire Replacement .

Did you find and correct the condition?

3000 ohms per ft

Go to Step 23

Go to Step 7

Switch the affected cylinder coil with a known good one.
If the fault follows the affected coil replace it. Refer to Ignition Coil Replacement .

Did you find and correct the condition?

Go to Step 23

Go to Step 15

Inspect the spark plug wires for proper routing and for the correct firing order.
If any spark plug wires are found to be misrouted, reroute as necessary. Refer to Spark Plug Wire Replacement .

Did you find and correct the condition?

Go to Step 23

Go to Step 9

With a DMM, test spark plugs for internal short to ground. Replace any grounded spark plugs found. Refer to Spark Plug Replacement .

Did you find and correct the condition?

Go to Step 23

Go to Step 10

Remove the spark plugs. Refer to Spark Plug Replacement .
Inspect spark plugs for damage. Refer to Spark Plug Inspection .
If any spark plugs are found to be bad, replace the affected spark plugs. Refer to Spark Plug Replacement .

Did you complete the replacement?

Go to Step 23

Reconnect the 24X crank sensor.
Disconnect the IC Module connector C2.
Turn ON the ignition.
With a test lamp connected to a good ground, probe the IC module ignition 1 voltage circuit. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

Go to Step 12

Go to Step 17

Connect a test lamp between the IC module ignition 1 voltage circuit and IC module ground circuit.

Does the test lamp illuminate?

Go to Step 13

Go to Step 20

Disconnect the 7X crankshaft sensor connector from the IC module.
With a test lamp connected to battery positive voltage probe both the 7X high reference and low reference 7X circuits.

Does the test lamp illuminate when probing either circuits?

Go to Step 18

Go to Step 14

Connect a test lamp to ground.
Probe both the 7X reference high and 7X reference low circuits.

Does the test lamp illuminate when probing either circuits?

Go to Step 19

Go to Step 15

Ensure the battery voltage is within specifications.
Turn OFF the ignition.
Connect a DMM between the 7X high reference circuit and the 7X low reference circuit at the IC module harness connector.
Crank the engine while observing AC Duty Cycle percent .

Does the DMM indicate AC duty cycle present?

Go to Step 21

Go to Step 16

Test the 7X crank sensor circuits for the following conditions:

•

Opens

•	7X high Reference and 7X low reference circuits shorted together.

Repair any damaged wiring. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 23

Go to Step 22

Repair the open or short to ground in the IC module Ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Replace the fuse if necessary.

Did you complete the repair?

Go to Step 23

Repair the short to ground in the 7X Reference circuit which illuminated the test lamp. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

Repair the short to voltage in the 7X Reference circuit which illuminated the test lamp. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 23

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

Did you complete the repair?

Go to Step 23

Replace the IC module. Refer to Ignition Control Module Replacement .