Rather fundamental PNP switch question

[jforce]

Hi everyone. First post and let me say I've been both entertained and informed by your posts here since buying my S70 and thinking that I too could someday keep one of these fine cars running hundreds of thousands of miles.

Here's the question, could the switch be bad if I can start the car in P and N but have no forward gears? It's throwing codes P0705 and P1618, check engine light comes on of course as does the flashing up arrow.

And Could the situation occur say at a stoplight after driving for awhile (no touching gear shifter, car running, stop for the light, can't go when light turns green)?

I have twice in the last month also had a no crank/no start issue where I just waited awhile and the car starts right up. Somethings up with the PNP no doubt, but this 'perpetual neutral' situation is new.

If it's the trans, wouldn't i see other trouble codes pointing At transmission and not just the switch ? I have only an Autel EU702 reader so I suppose there could be other TCM codes, and I just don't see 'em.

Thought I would ask before tearing out the PNP switch with fingers crossed. I've read so many posts the last several days about tranny issues, but all I get are these codes and when it does decide to run, it shifts very smoothly and my tranny fluid is a nice red clear color with no bunt odor. Doesn't seem to be any particulates in the fluid either. No one has touched the fluid for 500-600 miles at least. I suppose previous owner may have done a partial drain before I got the car, but that's how long I've been driving it.

Appreciate any and all comments or experience, primarily with the function of the switch. It seems that it knows -sometimes at least- that it's in P or N, since it will most often start, but can a malfunctioning switch also cause loss of all forward gear engagement after start? Seems crazy. I can't imagine it can't see any gear besides P and N in this case. One or two of them maybe. But thought I'd ask. Thanks.

Jeff

[precopster]

The PNP tells the TCM (transmission control) which gear your selector is in.

It also acts as a start inhibitor when lever is in D, R or L by cutting power to the starter.

If it is that badly worn that it can't report the gear position it stands to reason that it will cause some strange symptoms. You can perform the PNP refurb as detailed here in the database (takes about 2 hours)

Personally I don't fully remove the switch from the harness; I just use the slack in the harness and work over the engine bay.

[jforce]

Thanks for the reply, Mike... got the switch out and opened up, cleaned it up according to some other how-to's and will report outcome.