P0305 Fault in 2005 Chrysler Pacifica AWD with Low Cylinder Compression - Diagnosis & Repair Advice
My 2005 Chrysler Pacifica AWD vehicle was involved in an accident and recently had a vacuum hose replacement for the cruise control system, along with a new harness installed. Since then, the check engine light has activated, and I've noticed intermittent stalling and a 'putt-putt' sound during operation. I took the car to a Chrysler dealership, where they confirmed that the spark plugs are functioning properly but reported that cylinder 5 is registering only 100 psi compression, while all other cylinders show approximately 175 psi. Injector testing also came back normal. I'm concerned about what could be causing this discrepancy. The dealer requested $800 just to perform further diagnostics and confirm the root cause. I’m hesitant—especially as a woman—and feel I might be being overcharged, though I understand that accurate diagnosis requires proper tools and procedures. I’ve been able to retrieve the DTC code P0305 using my ignition key without paying for diagnostic services, which has raised some concerns. What additional checks should I consider? Is it possible that the low compression is due to a blown head gasket or faulty valves? Could the accident have caused internal engine damage leading to this issue? Any expert advice on next steps would be greatly appreciated.
A compression difference of approximately 75 psi between cylinder 5 and the others strongly suggests a head gasket failure or a defective valve, both of which are common in this engine model. The $800 fee is likely not for diagnostics but rather for removing the cylinder head to perform repairs—this is standard practice when low compression is confirmed. You're not being taken advantage of; you're being quoted a fair and necessary repair cost. If they were selling replacement parts like spark plugs, injectors, or PCM modules without first identifying the actual issue, that would be problematic. The cruise control repair is unrelated to this engine problem—however, if the accident caused overheating, it could have contributed to internal engine damage triggering the P0305 code.