Possible Causes:
* Engine Misfire: The most important thing to address FIRST is the engine misfire. A misfire can cause erratic signals to the transmission control module (TCM), leading to the flashing overdrive light. Diagnose and fix the misfire *before* tackling the transmission. Common causes of misfires include:
* Spark plugs and wires: Inspect for wear, damage, or loose connections.
* Ignition coil(s): Test the coils for proper operation. A faulty coil can cause a misfire in one or more cylinders.
* Mass Airflow Sensor (MAF): A faulty MAF sensor can provide incorrect air/fuel mixture readings leading to a misfire.
* Throttle Position Sensor (TPS): A faulty TPS can also affect the air/fuel mixture.
* Fuel injectors: A clogged or faulty injector can cause a cylinder to misfire.
* PCV Valve: A clogged PCV valve can cause excessive crankcase pressure impacting engine performance and potentially triggering a misfire.
* Transmission Control Module (TCM) Issues: The misfire might have damaged or stressed the TCM. While less likely than a simple misfire, it's possible the TCM is malfunctioning or needs reprogramming.
* Transmission Fluid Level and Condition: Check the transmission fluid level. Low fluid or severely contaminated fluid can cause problems and trigger the light. While less directly related to a *flashing* light after a misfire, it's worth checking.
* Transmission Speed Sensor (VSS): A faulty VSS can provide inaccurate speed signals to the TCM, potentially causing issues.
* Vehicle Speed Sensor (VSS) Connector: Sometimes, a simple problem like a loose or corroded connector on the VSS can cause problems.
Troubleshooting Steps:
1. Address the Engine Misfire: Use an OBD-II scanner to get diagnostic trouble codes (DTCs). This will pinpoint the source of the misfire. Repair the misfire. Once the misfire is fixed, clear the codes and test drive the vehicle. The overdrive light *may* go out.
2. Check Transmission Fluid: Check the fluid level and condition. If low, add fluid. If the fluid is dark, burnt, or smells bad, it needs to be changed.
3. Check the VSS and Connector: Inspect the VSS and its connector for any damage or corrosion.
4. OBD-II Scan for Transmission Codes: After addressing the misfire, scan again for any transmission-related DTCs. This will help narrow down the problem if the overdrive light persists.
5. TCM Issues (Advanced): If all else fails, the TCM may need to be inspected or replaced. This is best left to a qualified mechanic, as it involves more advanced diagnostics.
Important Note: A flashing overdrive light is a serious indication. Continued driving with this light flashing could cause further damage to the transmission. It's best to address the issue promptly. If you're not comfortable performing these checks yourself, take your Crown Victoria to a qualified mechanic for diagnosis and repair.
