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Old 12-07-2015, 05:17 AM   #1
eepp
 
Drives: Yaris 2008 RS
Join Date: Apr 2013
Location: Montreal, Canada
Posts: 17
P0705: Yaris 2008 stuck in first gear in D position

Hello people!

So yesterday I drove my A/T Yaris 2008 HB and everything was working fine.

This morning, I start it, no problem, then go to D and start driving. The transmission won't up shift from 1st to 2nd! Other manual gears except 2 and 3 work properly (P, R, N, L). Also, the current gear is not visible on the dashboard, except 2 and L which both display L.

I was afraid I had a serious transmission issue.

I have a CEL on since a few months because of some evap. problem I didn't fix yet (probably topped off fuel tank or defective fuel cap; out of scope any way), so I didn't look at DTCs at first.

Then my dad suggested that it's probably an electrical issue more than a transmission issue since the transmission won't even try to up shift and considering the weird invisible gear character thing on the dashboard.

I grabbed by USB OBD-II device and checked the codes again. Now I see it: P0705, which is exactly this: issue with the park/neutral position switch (PNP).



So I'm not too much into car mechanics (I'm a computer engineer), but from what I understand, this switch converts the mechanical position of the gear lever (i.e. current selected manual gear) to asserting a specific electrical contact. Here are the contacts to check depending on the gear lever position:



And P0705 indicates one of the following conditions:
  1. Any 2 or more of P/R/N/D/2/L signals are ON simultaneously for 2 seconds
  2. All switches are OFF simultaneously for P/R/N/D/2/L positions for 60 seconds
  3. L or 3 input signal is ON for P, R or N position for 2 seconds

I suspect that L is shorted because it's the only one that is displayed on the dashboard, and it is also displayed when I keep the gear lever between two positions, like the ECU does not receive anything else than L, so it displays L on the dashboard.

I cannot confirm right now, but will do tomorrow, because it's 4 AM right now (dark and cold outside).

My guess is that I would need to remove the whole PNP and open it to clean it and make sure L is not shorted, unless the problem is in the cable itself. No way I will replace the PNP because it's either:
  • Expensive as fuck when new (CAD$200+)
  • Slow as fuck to get when used (e.g., 2-3 weeks from China on eBay)

I'm thinking about a "short-term" solution right now to avoid removing and cleaning the PNP: cut/isolate the LL pin on the connector, so that (if L is really the one shorted) the ECU stops seeing this pin enabled. I could still use the L gear, because if I understand correctly, it's a single gear and does not need any ECU intervention. Using L would bring back P0705 and the CEL however (unless I use this gear for less than 60 seconds), because the ECU would not be getting any signal from the PNP, therefore raising this DTC. But whatever... as long as the car brings me to work and can carry a Christmas tree...

What do you think?

I would appreciate if any of you could share some experience and tips regarding the PNP!

I'll update this thread as I progress towards a solution, whatever it is.
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Old 01-20-2018, 05:19 AM   #2
eepp
 
Drives: Yaris 2008 RS
Join Date: Apr 2013
Location: Montreal, Canada
Posts: 17
Ok so it's been a long time, but for the record, I ended up buying and installing a new PNP switch.

I wanted to open the dirty one and clean it, but the case is fastened with rivets, and the place I went that had a lift (you really need a lift) did not have what's required to drill the rivets and replace them. And I could not drive elsewhere with the PNP switch removed because I need it to drive (I mean to drive in D position to the other place which is too far to drive in 1st gear).

Therefore I bought a new, OEM one from the Arab Emirates (cheapest I could find online) for about CAD$200.

The Yaris service manual is straightforward enough to know how to reach this part. It implies lifting the car, removing some bottom plastic splash shields, removing nuts and a cable.

TIP: Don't be afraid to use a lot of loosenut as some nuts can be REALLY stuck. Just follow the service manual and when it asks to remove a nut, spray loosenut and remove it.

I still have this old PNP switch. I still need to open it and clean it, and then decide whether to sell it or keep it as a spare for the next episode.

Last edited by eepp; 01-22-2018 at 12:24 PM.
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Old 01-21-2018, 01:49 AM   #3
yaris4062007
 
Drives: 07 BB yaris / 06 Mustang Gt
Join Date: Apr 2007
Location: northern california
Posts: 131
Did you have to disconnect cable to pnp?
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Old 01-22-2018, 12:24 PM   #4
eepp
 
Drives: Yaris 2008 RS
Join Date: Apr 2013
Location: Montreal, Canada
Posts: 17
Quote:
Originally Posted by yaris4062007 View Post
Did you have to disconnect cable to pnp?
Of course: I changed the whole unit.
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