The SES light on a 1988 Firebird is controlled by the engine's computer (ECM or PCM). The light comes on due to a fault code stored in the ECM's memory. You absolutely need to retrieve that diagnostic trouble code (DTC). Without that code, any troubleshooting is just guesswork.
Here's how to proceed:
1. Obtain a code reader: You'll need a code reader compatible with OBD I systems (that's what your car uses). These are less common than OBD II readers but still available online or at auto parts stores. Some older scan tools might only give you a single-digit code (a less specific code).
2. Retrieve the diagnostic trouble code(s): Connect the code reader and follow its instructions to read the codes from your ECM. Write down the code(s) *exactly*.
3. Look up the code(s): Once you have the code(s), you can search online (e.g., using a search engine like Google or Bing) for "1988 Firebird OBD1 DTC [Your Code Number(s)]." This will give you a much better idea of what the problem is.
4. Possible sensor locations (but only after getting the code): Once you know the code, you'll have a specific sensor to check. However, common culprits in older cars that can trigger the SES light include:
* Mass Air Flow (MAF) sensor: Measures air entering the engine. Located somewhere near the air filter housing.
* Throttle Position Sensor (TPS): Senses the throttle plate position. Usually on the throttle body.
* Crankshaft Position Sensor (CKP): Important for engine timing. Location varies depending on the engine (check your repair manual).
* Oxygen Sensor(s): Measures oxygen in the exhaust. Located in the exhaust manifold or header.
* Coolant Temperature Sensor: Located in the engine block or cylinder head.
Important Considerations:
* Repair Manual: A repair manual specific to your 1988 Firebird (with the exact engine type) is invaluable. It will show you the location of all sensors and components, as well as diagnostic procedures.
* Safety: Work on your car in a well-ventilated area. Be careful around hot engine parts and electrical systems.
* Professional Mechanic: If you are not comfortable working on your car yourself, take it to a qualified mechanic. Ignoring the SES light can lead to further damage.
Simply checking sensor wires without knowing *which* sensor is faulty is a waste of time and effort. Get the code first. That will point you in the right direction.
