Here's a breakdown of the likely culprits and why manual shifting works while automatic doesn't:
* Solenoids: These electrically controlled valves direct fluid flow within the transmission to engage the correct gears. If one or more solenoids are faulty or sticking, the automatic system won't be able to select the correct gears, but manual shifting bypasses the faulty solenoid(s) allowing you to select the gears mechanically.
* Shift Linkage/Cables (if applicable): While less likely given the widespread issue across gears, a problem with the mechanical linkage connecting the shifter to the transmission could prevent the automatic selection of gears but not affect manual shifting (though less common in electronically controlled transmissions like the Intrigue likely uses).
* Valve Body: The valve body houses the solenoids and other hydraulic components that control gear selection. Internal damage or wear within the valve body could be causing the malfunction.
* Transmission Computer/PCM: While less probable (since all gears are affected), a faulty transmission control module (TCM) or the Powertrain Control Module (PCM) could be sending incorrect signals to the solenoids, but manual override would still allow shifting. However, this is less likely than a mechanical issue within the transmission.
* Low Transmission Fluid: While less likely to cause a complete loss of gears 1-3, critically low fluid can lead to transmission problems. Check the fluid level *immediately*. Low fluid often indicates a leak, which needs addressing regardless.
What to do:
1. Check the Transmission Fluid: This is the first and easiest step. Check the level and condition of the transmission fluid. Is it low? Is it dark, burnt, or smells burnt?
2. Have it Diagnosed Professionally: Given the complexity of automatic transmissions, you'll almost certainly need a professional mechanic to diagnose the specific issue. They have the tools and expertise to test the solenoids, valve body, and transmission computer. A simple diagnostic scan can often pinpoint the problem quickly.
3. Prepare for Repair Costs: Transmission repairs can be expensive, especially if internal components need replacing. Get multiple quotes before committing to any repairs. Consider the age and condition of the vehicle to determine if the repair cost is justified. A rebuild or replacement transmission might cost more than the vehicle is worth.
Driving the car in this condition could cause further damage to the transmission. Limit driving to only what is absolutely necessary until a proper diagnosis and repair can be made.
