Unfortunately, directly checking an ECM is difficult without specialized equipment. You can't just visually inspect it for obvious damage. Here's a breakdown of how to approach this:
1. Rule Out Other Possibilities (Again):
* Fuel Pressure: Even if you've checked the fuel pump, ensure you're getting the *correct* fuel pressure at the fuel rail. A weak pump might still provide enough to create some spark but not enough for a proper start. You'll need a fuel pressure gauge for this.
* Crankshaft Position Sensor (CKP): A bad CKP sensor won't prevent the engine from cranking, but it will prevent a proper spark *timing*. The engine might crank, but fail to fire. These are relatively inexpensive to replace and easy to access.
* Cam Position Sensor (CMP): Similar to the CKP sensor, a faulty CMP will disrupt spark timing.
* Ignition Module: This component distributes the spark to the correct cylinder. Failure is possible.
* Wiring and Connections: Carefully inspect all wiring harnesses and connectors related to the ignition system, fuel system, and ECM itself. Look for corrosion, broken wires, or loose connections. Pay close attention to grounds.
2. Testing the ECM (Indirect Methods):
Since direct testing requires an oscilloscope and a deep understanding of the ECM's signals, you'll be relying on indirect methods:
* Diagnostic Codes: Does your Cavalier have a check engine light (CEL)? If so, a scan tool (OBD I scanner for your year) can retrieve diagnostic trouble codes (DTCs) that might point to the ECM or a related problem. Auto parts stores often offer free code reading services.
* Visual Inspection (ECM itself): Remove the ECM (locate it – often under the dash or in the engine bay) and visually inspect it for any obvious signs of damage (burns, cracks, corrosion). This is a low-probability find, but worth a quick look.
* Professional Diagnosis: The most reliable method is taking your Cavalier to a qualified mechanic or auto electrician. They have the tools (scanners, oscilloscopes) and expertise to diagnose ECM problems accurately.
3. ECM Replacement:
If all other components check out, replacing the ECM is a possibility. However, this is an expensive component and the wrong ECM could lead to further problems. Make absolutely sure you get the correct ECM for your specific 1992 Chevy Cavalier engine and options. The part number should be clearly marked on your current ECM.
In summary: Before jumping to an ECM replacement, exhaust all other possibilities. The indirect testing methods above are your best bet to get closer to the problem. Professional diagnosis is often the most efficient and cost-effective approach in these situations.
