1. Verify the Basics (Before blaming modules):
* New Switch Correctly Installed: Double-check the ignition switch installation. A wiring error is the most common cause after such a replacement. Make absolutely sure all wires are correctly connected, and that the switch itself is seated properly. A wiring diagram for your specific year and model Aspire will be invaluable here.
* Fuses and Relays: Inspect all fuses and relays related to the ignition system. A blown fuse or a faulty relay can prevent the system from functioning. Check the owner's manual to locate the appropriate fuses and relays.
* Battery Voltage: Ensure the battery has sufficient voltage. A weak battery can cause intermittent or complete failure of the ignition system. Test the voltage with a multimeter.
* Ignition Coil: Test the ignition coil's primary and secondary windings for continuity and resistance using a multimeter. A faulty coil won't produce the spark needed for combustion.
* Cranking: Does the engine crank (turn over) when you turn the key? If not, the problem might be before the ignition system; the starter, battery cables, or even the ignition switch itself (despite the recent replacement) could be at fault.
2. Addressing Modules:
* Ignition Control Module (ICM): The ICM is a crucial component that controls the ignition timing and spark delivery. A faulty ICM is a common cause of no-start issues. Testing it requires a multimeter and some specialized knowledge of its operation and wiring. A simple visual inspection may reveal obvious damage, but a proper test is crucial.
* Engine Control Module (ECM): The ECM controls various engine functions, including the ignition system. While less likely than the ICM to be the primary cause after an ignition switch replacement, a faulty ECM is still possible. ECM testing usually requires specialized equipment and diagnostic software.
3. Testing and Diagnosis:
* Professional Mechanic: Given the complexity of automotive electrical systems, seeking help from a qualified mechanic is highly recommended. They have the tools (scanners, multimeters) and experience to diagnose the issue quickly and accurately.
* Wiring Diagrams: Obtain a wiring diagram for your 1997 Ford Aspire. This will be essential for tracing the electrical circuits and identifying potential problems. Online resources or a repair manual can provide these.
In short: Before assuming it's a faulty ICM or ECM, meticulously check all the simpler possibilities. If those check out, then focus on testing the ICM, but consider professional help because diagnosing ECM problems is often best left to the experts. The cost of a misdiagnosis could easily outweigh the cost of professional help.
