2004 Pontiac Bonneville

The 2004 Pontiac Bonneville is a full-size sedan known for its comfortable ride and spacious interior. Engine options included the 3.8L Series III V6 (205 hp, 230 lb-ft of torque) and the supercharged 3.8L Series III V6 (240 hp, 280 lb-ft of torque) in the GXP trim. Both engines were paired with the 4T65E 4-speed automatic transmission. Owners often praised the Bonneville for its smooth ride, powerful engine options, and comfortable seating. Common complaints included electrical issues, particularly with the window motors and various sensors, as well as some suspension problems.

Engine

3.8L Series III V6 (L36)

• Intake Manifold Leak
  • Description/Symptoms: Coolant leaking externally, overheating, low coolant level. The plastic portion of the intake manifold cracks and leaks coolant.
  • Solution: Replace the intake manifold with an updated version that uses an aluminum coolant elbow.
  • Estimated Cost to Fix: $400 - $700+
  • Recalls: None Found
• Fuel Injector Failure
  • Description/Symptoms: Rough idle, misfires, poor fuel economy.
  • Solution: Replace faulty fuel injector(s).
  • Estimated Cost to Fix: $150 - $300+ per injector
  • Recalls: None Found

3.8L Supercharged Series III V6 (L67)

• Supercharger Failure
  • Description/Symptoms: Whining noise from the supercharger, reduced power, check engine light. The supercharger coupler, bearings, or rotors may fail.
  • Solution: Rebuild or replace the supercharger.
  • Estimated Cost to Fix: $800 - $2000+
  • Recalls: None Found
• Intercooler Issues
  • Description/Symptoms: Overheating, reduced performance. The intercooler can become clogged or leak.
  • Solution: Clean or replace the intercooler.
  • Estimated Cost to Fix: $300 - $800+
  • Recalls: None Found

Transmission

4T65E 4-Speed Automatic

• Torque Converter Failure
  • Description/Symptoms: Shuddering during acceleration, poor fuel economy, transmission slipping.
  • Solution: Replace the torque converter.
  • Estimated Cost to Fix: $800 - $1500+
  • Recalls: None Found
• Pressure Control Solenoid Failure
  • Description/Symptoms: Harsh shifting, erratic shifting, transmission slipping.
  • Solution: Replace the pressure control solenoid.
  • Estimated Cost to Fix: $300 - $600+
  • Recalls: None Found

Suspension

• Rear Air Suspension Failure (GXP)
  • Description/Symptoms: Rear of the car sagging, compressor not working, rough ride. Air bladders leak or the compressor fails.
  • Solution: Replace the air bladders or the air compressor, or convert to a traditional coil spring suspension.
  • Estimated Cost to Fix: $500 - $1500+
  • Recalls: None Found
• Front Strut Mount Failure
  • Description/Symptoms: Clunking noise from the front suspension, especially when turning.
  • Solution: Replace the strut mounts.
  • Estimated Cost to Fix: $300 - $600+
  • Recalls: None Found

Electrical

• Window Motor Failure
  • Description/Symptoms: Window not working, slow window operation. The window motor fails.
  • Solution: Replace the window motor.
  • Estimated Cost to Fix: $150 - $300+ per window
  • Recalls: None Found
• Body Control Module (BCM) Issues
  • Description/Symptoms: Intermittent electrical problems, such as malfunctioning lights, door locks, or radio.
  • Solution: Repair or replace the BCM.
  • Estimated Cost to Fix: $300 - $800+
  • Recalls: None Found
• Ignition Switch Failure
  • Description/Symptoms: Car stalls, unable to start, intermittent electrical issues.
  • Solution: Replace the ignition switch.
  • Estimated Cost to Fix: $200-$500+
  • Recalls: None Found

Exterior

• Door Handle Breakage
  • Description/Symptoms: Door handle breaks off or becomes difficult to use. The plastic mechanism inside the handle fails.
  • Solution: Replace the door handle.
  • Estimated Cost to Fix: $100 - $250+ per handle
  • Recalls: None Found

Interior

• Sunroof Issues
  • Description/Symptoms: Sunroof motor failure, sunroof track malfunctions, leaking sunroof.
  • Solution: Repair or replace the sunroof motor or track.
  • Estimated Cost to Fix: $200 - $800+
  • Recalls: None Found
• Driver Information Center (DIC) Failure
  • Description/Symptoms: Pixels missing on the DIC display, making it difficult to read.
  • Solution: Replace or repair the DIC.
  • Estimated Cost to Fix: $100-$300+
  • Recalls: None Found

Summary

The 2004 Pontiac Bonneville, while praised for its comfort and power, has several common issues. Engine-related problems, such as intake manifold leaks and supercharger failures (on the GXP), can be moderately expensive to repair. Transmission issues, particularly with the torque converter, are also common and can be costly. Electrical problems, especially window motor and BCM failures, are also frequent complaints. Suspension issues, mostly related to the rear air suspension on the GXP trim, can add to the overall maintenance costs. The severity of these issues ranges from minor inconveniences to major mechanical failures, with repair costs ranging from a few hundred to several thousand dollars depending on the specific problem.