Engine shut off while driving and will not start, code PO420

Hi:

If there is no spark and you replaced the crank and cam sensors, my next suspect is the ignition control module. The module is under the three coils. The ICM is responsible for the following:

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Ignition control module (ICM) and ignition coils
Three dual tower ignition coils are mounted to the ICM, and are serviced individually. The ICM performs the following functions:
- The ICM receives and processes the signals from the CKP sensor B.
- The ICM determines the correct direction of the crankshaft rotation, and cuts spark and fuel delivery to prevent damage from backfiring if reverse rotation is detected.
- The ICM determines the correct coil triggering sequence, based on the 7X CKP signal. This coil sequencing occurs at start-up, and is remembered by the ICM. After the engine is running, the ICM will continue to trigger the coils in the correct sequence.
- The ICM produces and inputs 3X reference signals to the PCM.
- The ICM contains the coil driver circuits that command the coils to operate.

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Now, what I suggest is to remove the module and have it tested. Most nationally recognized parts stores are able to do this and will for free.

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Here are the directions for removal and replacement. However, in addition to this, I strongly recommend having the converter issue resolved. If it is plugging, it will cause power loss and can cause internal engine damage.

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2003 Pontiac Grand AM V6-3.4L VIN E
Procedures
Vehicle Powertrain Management Relays and Modules - Powertrain Management Relays and Modules - Ignition System Ignition Control Module Service and Repair Procedures
PROCEDURES
REMOVAL PROCEDURE

pic 1

1. Disconnect all the electrical connectors at the ignition control module.
2. Note position of spark plug wires for installation and disconnect the spark plug wires from ignition coils.
3. Remove the screws securing coil assemblies to ignition control module.
4. Disconnect the coils from ignition control module.
5. Remove the ignition control module from the bracket.

INSTALLATION PROCEDURE
1. Install the ignition control module on the bracket.

Pic 2

2. Install the coils to ignition control module.
3. Install the screws.

NOTE: Refer to Fastener Notice in Service Precautions.

Tighten
Tighten the screws to 4.5 N.M (40 lb in).

4. Connect the spark plug wires as noted during removal.
5. Connect the electrical connectors to the ignition control module.

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Let me know what you find or if you have other questions.

Take care,
Joe

Hi,

It was starting to burn because the fuse you installed was too strong for the wiring to handle. Fuse amperage is based on the gauge (thickness) of the wire it supplies power to. The smaller the wire, the less power it can handle. By putting a much larger fuse in place of a small one, you allowed more power to flow through the wire before the fuse would blow. The smaller wire has too much resistance for larger amounts of power. Hence, the 10 amp fuse. Resistance causes heat which caused the problem. I'm just glad you weren't hurt and it didn't catch fire. Never exceed the manufacturer's recommend amperage for fuse replacement. Fuse amperage is determined based on the gauge of wire they power.

The most likely cause of the fuse blowing is because there is a short somewhere in the system. That is a point where the power from the fuse is grounding, causing too much of a power draw for the fuse and it to blows.

Now here is what I need you to do. First, disconnect the negative terminal from the battery. Next, unplug the ICM. Once battery power is gone and the ICM is disconnected, I need you to check the pink wire at the ICM for continuity to ground. The wire is pink in color.

There should not be continuity to ground, so if there is, that means the wire is shorted to ground at some point. At that point, either replace the wire or trace it for damage to the insulation on it which is allowing the copper wire to touch something metal.

Here are a few links to help:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

Also, if you could upload a pic of where the smoke was coming from and any damage to wiring, it may help. I hate to say this, but it also sounds like you damaged both the coil and new ICM. However, since the fuse was blown, the original ICM may still be good.

I attached two pics. The first is the fuse box. I am just confirming I have the correct fuse you are referring to. The second shows the wiring. I have an arrow pointing to where the power from fuse 41 goes to the ICM. The pink wire is the one needing checked.

Let me know what you find or if you have questions. Please be careful. Although a car battery in and of itself can not shock you, it most certainly can cause fires.

I will watch for your reply.

Take care,
Joe