* Transmission Fluid Level and Condition: Low transmission fluid is a very common culprit. Check the fluid level (with the engine running and warmed up) and its condition. Brown, burnt-smelling fluid suggests it needs to be changed or there's a more serious internal problem.
* Transmission Temperature: Overheating can cause the light to blink. This could be due to low fluid, a faulty transmission cooler, or a more severe internal transmission issue.
* Internal Transmission Problems: This is the most serious possibility. Blinking can signify a variety of internal issues, including:
* Solenoid Problems: These electrical components control various functions within the transmission. A faulty solenoid can prevent proper shifting and trigger the light.
* Torque Converter Issues: A malfunctioning torque converter can cause slippage and lead to the blinking light.
* Worn Clutch Packs or Bands: These components wear out over time, affecting shifting and leading to the light.
* Low Transmission Pressure: This could indicate a pump problem or other internal leak.
* Transmission Shift Solenoid Circuit Issues: Problems in the electrical circuit controlling the transmission solenoids can cause the light to blink. This often involves faulty wiring, connectors, or the transmission control module (TCM).
* Vehicle Speed Sensor (VSS): A faulty VSS won't accurately relay the vehicle's speed to the transmission control module, leading to incorrect shifting and a blinking light.
* Transmission Control Module (TCM): The TCM is the "brain" of the transmission. A faulty TCM can cause numerous issues, including a blinking overdrive light.
What to do:
1. Check the transmission fluid: This is the easiest and most important first step.
2. Get a professional diagnosis: A blinking overdrive light almost always means a problem needs professional attention. A mechanic can use a scan tool to read the transmission codes stored in the car's computer. This will pinpoint the exact problem more accurately than any guesswork. Ignoring the problem could lead to significant and expensive transmission damage.
Don't attempt to diagnose or repair this yourself unless you have significant experience with automatic transmissions. Improper repair can worsen the damage.
