Buick Century Won't Start in Park, Gear Linkage Issues

As someone with moderate experience working on cars, I had a very similar issue with my 2001 Buick LeSabre last year. The symptoms were nearly identical, problems with the gear shifter not properly engaging neutral position and transmission issues when shifting. The main problem turned out to be a defective transmission control unit, which was affecting the neutral position sensor and causing erratic gear shifting patterns. Initially thought it might just be the shifter mechanism, but diagnostic testing revealed the more complex issue. Had to take it to a transmission repair specialist who confirmed the control unit failure. The total repair cost was around 1000, including parts and labor. The fix resolved both the starting issues and the rough shifting problems completely. Before suggesting specific solutions for your Century: What error codes showed up in your scan? Is the park brake working normally? Does the transmission fluid level and condition look good? Are there any unusual sounds when shifting between gears? This information would help determine if your issue matches what I experienced with the control unit or if it might be something different.

Last service was at 190725 KM. My scan showed P0705 and P0708 codes. The park brake works fine but the transmission fluid looks a bit darker than usual. When shifting gears, there is a noticeable clunking sound, particularly between drive and reverse. The transmission repair quote I got seemed high at €1400, so wanted to get some second opinions before proceeding. The gear linkage feels looser than it should be, which makes me wonder if this could be fixed without a full transmission repair job. The check engine light stays on constantly now, even after clearing the codes.

Based on those trouble codes and symptoms, this does indeed sound very similar to what I experienced with my LeSabre. The P0705 and P0708 codes typically indicate transmission range sensor circuit issues, which align with the shift lock and gear shifter problems you described. The dark transmission fluid and clunking sounds during gear changes are concerning signs of potential transmission wear. In my case, what initially seemed like just a gear linkage problem turned out to be more serious transmission issues that required professional attention. While the €1400 quote is higher than what I paid, transmission repair costs can vary based on the specific components needing replacement. My repair initially started as a sensor replacement but revealed additional transmission problems that needed addressing. Before authorizing the full repair, consider having them: 1. Check the transmission range sensor connections 2. Verify shift lock solenoid operation 3. Perform a transmission fluid analysis 4. Test the park brake interlock system These preliminary checks might identify a less expensive fix, though based on my experience with similar transmission failure symptoms, be prepared for the possibility of more extensive repairs being necessary. When my transmission issues were fully resolved, the gear shifting returned to normal and the check engine light stayed off permanently. Make sure any repair includes a proper diagnostic test afterward to confirm all systems are functioning correctly.

The clunking sound and P0705/P0708 codes combined with dark fluid definitely suggest this could be more serious than I initially hoped. Thanks for the detailed comparison to your LeSabre situation, it helps confirm my suspicions about the transmission issues being beyond just the gear linkage. The shift lock problems and rough shifting between gears match exactly what you described. Given the constant check engine light and transmission symptoms getting worse, I should probably stop putting this off and get it properly fixed, even at the €1400 price point. Better than risking more expensive transmission repair down the road. Will ask the shop to do those preliminary checks you suggested, especially the transmission range sensor connections and fluid analysis. If it needs the full repair like yours did, at least I know what to expect cost-wise and that fixing it properly resolved all the symptoms. Really appreciate the detailed feedback, helps justify the repair cost knowing someone else had similar transmission issues fixed successfully.