PO705 Transmission range sensor PRNDL, isn't the switch.

@gearcruncher or any trans guys

On my 2008 Tacoma 6 cyl. transmission, I'm getting a P0705 code and the trans will not upshift to D and stays in 4. All other shift functions are good. The 2 to L functions and all dash lights for gears illuminate correctly. I tested all connections walking down the schematic.

I believe the improper signal is coming from either the ECU or the transmission as I see in the troubleshooting notes that the problem nay be in the SL1 and SL2 solenoids. I did replace the PRNDL switch, but it checked out regardless.

I see that troubleshooting states that its getting conflicting signals what gear its in.

I did check out all wiring to PRNDL switch and NSS and also ohmed all solenoids and they were in spec.

I heard clicks from all except SL1 and SL2 when applying 12V back probing the connector at the ECU. I see from troubleshooting chart that these solenoids may be the issue.

This is a genuine Toyota rebuilt transmission that just passed its warrantee unfortunately. It was working fine until just now. Mothership is trying to make me replace the harness @4600.00 but I'm Not going there! I ohmed out the harness and all is good. Toyota will not diagnose further unless I pay for a harness replacement, Boo!

Where should I go next?

Drop the pan and see if I can get SL1 & SL2 to operate?

Many thanks!!

 

The TSB linked below is why they want to replace the harness.

If we look at code set criteria, the P0705 sets when the ECM detects that A: 2 or more Transmission Range Switch (P, R, N, D, 4, 3, 2 or L) are on simultaneously for more than 2 seconds or B: No Transmission Range Switch signals are on for 60 seconds.

I'd be looking at the switch inputs in scan data to see which one(s) aren't working properly and focus on those circuits, shouldn't be hard to find which one isn't working properly and then backprobe and check voltages with a meter.

 

Dm93
Thanks for the feedback and tech bulletin!
I'll take a look at the connector in the kick panel, but I would think It would show up on the test.
I did go through the input voltages while looking for any on simultaneously and all checked out.
I suspect sticking SL1 & 2 but wonder how they would set a code.
It does state in troubleshooting somewhere in the trans section...

 

The solenoids will set other codes, the P0705 deals specifically with the range switch.

I would really want to look at scan data, that's the only way to see what the ECM is seeing so you know what circuit to be checking.

 

Ok, got a friend to look at freeze frame and discovered that no 12V signal on black wire to ECU pin #20 when shifted to D, but have when in 4.
Dash lights with both D and 4.
Schematic looks like disconnected at J4

 

Ok, discovered problem on getting P0705 !!

Now upshift to 5th

Pin #21 on ECU connector D(7) for Drive signal color L-B had 12V when in drive or 4, but, when scanner connected did not show!

Bad pin fit! Probably due to some tech messing around on the wrong side if connector with a probe expanding the female side instead of back probing

Moral of the story, the testing for voltage and duplicated signals did not prove and must scan!

The P0705 troubleshooting chart doesn’t say you will produce a code if the ECU doesn’t see 12V on pin 21 when shifter is in 4 as schematic shows.

these tiny pins and ECU connections bit me more than once!

 

That's why I only use flow charts as a guide, they will have you going on an expedition for hours and can still lead to the weong conclusion for something that can be checked in a few minutes with a scan tool, meter, and test light if you know what your looking for.