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Oldsmobile Alero Ignition Coil Troubleshooting

by Tim Petruccio

General Motors introduced the Oldsmobile Alero in 1999. The 2001 Oldsmobile Alero was equipped with the option of a 2.4-liter in-line 4-cylinder engine, or a 3.4-liter V-6 engine. Both engines use a coil module and coil packs in the ignition system. Over time coil packs can wear out, and replacement becomes the only option. Testing the coil to make sure it is properly functioning is a good way to save money, and properly diagnose what is really wrong with the vehicle. Testing the coils on a 2001 Alero should take about one hour.

2001 Oldsmobile Alero: 2.4-liter, 4-cylinder Coil Testing Instructions

Raise the hood of the Alero. Position yourself in front of the vehicle so that you can access the coil pack on the top of the engine. Unplug the electrical harness from the coil. The ignition coil is located on the passenger top side of the engine. Simply pull the electrical connector from the coil module by hand.

Install an ohmmeter onto the electrical connector end of the control module. Connect the black lead wire from the ohmmeter to the plug end marked with a "-". Place the red lead from the ohmmeter onto the plug end marked with a "+".

Read the dial indicator on the ohmmeter. If the coil on the 2001 Alero, 2.4-liter engine does not read greater than 10,000 ohms of resistance, then the coil is bad and needs to be replaced.

2001 Oldsmobile Alero: 3.4-liter, V-6 Coil Testing Instructions

Raise the hood on the Alero. Label each spark plug wire on the coil module, using masking tape or labels. Write the numbers "1-2-3-4-5-and 6" on the spark plug wires from left to right.

Remove two spark plug wires from one of the coil packs. There are three coil packs, with two wires on each pack. Each pack controls two spark plugs. Set the plug wires on top of the engine, away from any moving parts. Step away from the vehicle so that no part of your body is touching the car at all.

Ask an assistant to turn the ignition key to the "Start" position for no longer than three second intervals. The vehicle will not start with the spark plug wires detached from the coil. Visually inspect the coil while the engine is cranking. Look for an electrical arc or spark to connect between the two coil towers while the engine is turning over. Ask your assistant to stop turning the key after no more than three intervals of cranking the engine. If the inspected coil has spark, then reinstall the spark plug wires and proceed to testing the next coil pack.

Remove the coil pack that has no spark, as well as the coil pack directly next to it. Use a 1/4-inch drive ratchet and socket to remove the two mounting screws that hold each pack in place. Switch the two coil packs by pulling both pack straight upward to remove them, and then placing them straight downward to attach them. Tighten the coil pack mounting screws back into the coil packs and module, with the 1/4-inch drive ratchet and socket. Leave the spark plug wires off of the suspected bad coil pack, but reattach all other spark plug wires.

Ask your assistant to again turn the key to the "Start" position for no longer than three second intervals. Do not touch the vehicle in any way while the engine is turning over. Visually inspect the coil pack towers of the suspected bad coil pack. If the coil pack does not have spark in this second position, then the coil is bad and needs replaced. If the coil that had no spark in its primary position has spark in the secondary position, then the coil module is bad and needs to be replaced.

Tip

  • Labeling the spark plug wires while testing the coils on the V-6, will help ensure that you can put all of the spark plug wires back in their original position. Moving spark plug wires to the wrong coil can destroy the coil module, as well as disrupt the firing order of the Alero engine.

Warning

  • Do not touch the vehicle with any portion of your body when your assistant is in the car turning the key. The electrical discharge from the coil can send a shock or arc to your body. The Alero only has 12-volt of electricity in the system, but the alternator puts out about 90 to 110 amps of electricity. Electrical shock can cause severe damage to the body, brain, and heart. Seek immediate emergency medical attention if you feel you receive any electrical shock during this testing procedure.

Items you will need

About the Author

Tim Petruccio is a professional writer and automotive mechanic. His writing combines more than 20 years of mechanical experience in automotive service, service management, automotive education and business ownership. He assisted in the automotive beta, which launched March 2011.

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