I am working with my daughters boyfriend trying to make a 2005 Civic Hybrid happy again.

A dying 12v battery had it doing all sorts of weird things for a while, but we got that...

One thing left...it won't let go of the Key when turned to park without removing the 12v battery power.....

When the 12v battery was giving him grief, he used the shift-lock bypass, so I am thinking that the Shift level isn't moving far "enough" to convince the system it is truly in Park. The car won't start in PARK but starts fine in NEUTRAL , so I am pretty sure it is a Park "detection" problem.

Questions:

- Where is the Sensor/switch that tells the Key Interlock Solenoid to release?
Is it the Park Pin Switch or the Transmission Range Selector?
Are there any fuses in that circuit I should check
Can I use a OBD reader to check the sensors?

- I read everything I could find but the Key Interlock Solenoid is barely mentioned, even less about what controls it, other than if various things get stuck it wants to keep the key, But we have brake lights, horn, and it starts fine in Neutral....

- Since he is using one of my "spare" 12v batteries, what is the "Best" 12v battery for this car? I know it is a 51R, but they go from cheep to outrageous. ($105 at wallmart, to $300 for a indestructible deep cycle one)