My 2002 Odyssey with 175K miles recently started having starting problems - would crank but not fire, but only occasionally. First I thought fuel line or fuel pump, then spark plugs etc. But have finally isolated problem to the ignition lock cylinder and immobilizer, but can't figure out which one of the two is the problem. Here is what I have observed.
1. When I try to turn the key in the ignition, sometimes the key won't turn at all and I have to jiggle it several times to get it to turn. At other times, the key will just turn smoothly.
2. After I do get the key to turn, I watch the immobilizer light on the dashboard. Most of the time, the green key lights up and goes off after couple of seconds. When this happens and I turn the key further, the van starts just fine.
3. Sometimes however, after I get the key to turn to position II, the immobilizer light comes on and keeps flashing. When this happens, if I turn the key further, the van cranks but does not fire. Then I turn the key back and start the process all over again. I may need to repeat this a few times but thus far, the immobilizer has always finally gone off and I have been able to fire up the car.

What I can't figure out is, because I am not able to turn the key at all sometimes (1 above), is the lock cylinder going bad? Is this related to the immobilizer sometimes remaining in flashing mode and not going off? I am trying to figure out if I need to replace the immobilizer or lock cylinder or both.
thanks in advance.

 

Would try spraying wd-40 into lock cylinder or use graphite.
Sometimes the pins in the lock will stick.
As for the immobilizer, the immobilizer-keyless entry control module is not reading the key properly
So, green key light comes on and immobilizer prevents the engine from starting
Some say cleaning the connector with electrical contact cleaner helps
I do not know. I would try dis-connecting and reconnecting a few times to see if it improves the connection??
Have seen where one person wrapped a coil of wire around the unit that goes around the lock cylinder.
I do not know. Would try to see if that helps??