Truck won't start; engine light, shifting issues, replaced park neutral switch

Hi All ....new member......although been reading many many post for years !!
Best source I know for knowledge about my Tacom. truck has never given me any trouble till now and I have read most of the post ....but still will not start.

Going to need some guidance:
07 TRD sport 4L 68k miles .....got the check engine light last week ... pulled into parts store to read codes
P0705 & P0778...truck runs fine.....starts .... accelerates through the gears normally ...but when you come to a stop...down shifts hard into second (2)and then (L)low. And 2 & L are not lit up on dash.......Read dozens of post about this code and start diagnosing...checked drivers side kick panel 4 plug junction box… No corrosion or sign of moisture. Get under the truck and check Park neutral switch… Disconnect plug and use contact cleaner plug it back in and now I don’t have P or N illuminated on the dash or 2 & L...of course...will not start !!
So... just replaced park neutral switch per instructions from TW.
Now still don’t have P or 2 or L....but N, D,4,3 all illuminated....and still no start !!
Really frustrated and can’t think straight !!
Any suggestions or advice would be greatly appreciated !!!!

 

Sounds like you have a wiring fault.
Start by clicking the Spoiler:No Crank button in the link below.
Report your findings here.
We will be more than happy to help you along the way.

https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042155

 

Sounds like an issue with the connector at the switch, the switch itself (or it's not adjusted properly), or a wiring issue.
Is there corrosion in the connector?
Will it crank in neutral?

You can check all the signals except the starting circuit from the switch backprobing connector PB on the junction box behind the glovebox.
Each pin should be at battery voltage with the shifter in the respective position, the rest should be at or near 0v.

Pin 5 (Green/Black) Park
Pin 6 (Red/White) Reverse
Pin 8 (Blue/White) Neutral
Pin 3 (Blue/Black) D & 4
Pin 1 (Yellow) 3
Pin 7 (Red/Yellow) 2 & 1




The Neutral Safety Switch portion of the range switch is Pins 4 (Violet) (Power in from the STA Fuse (7.5A) and 5 (Black/Yellow) (Power out to the STA Relay) at the switch connector.

 

Thanks DM ....There is no corrosion on the face of the female plug to the PN switch. Also sprayed contact cleaner before Plugging it into you PN switch.
Replaced PN switch very carefully and believe it is installed correctly...it is an OEM part so not very likely its defective.
Will not crank in any shifter position
Been reading for hours....now I’m thinking it might be loose wires inside female connection???
Not very Electrically inclined .....can check voltage at the plug with basic voltmeter if you can explain how to do it and what voltage to look for .

 

It's certainly possible it's a pin fitment issue, you haven't been poking things into the pins to check/clean them have you?

I can try, remember you don't want to shove anything into the pins. All you need to do is touch the metal part of the pin with your test lead.

At the range switch connector Pin 2 (Yellow) should have power with the key on (since some of your indicator lights work I have to assume this is good), Pin 4 (Violet) should have power with the key in the crank position.

 

Thank you for your guidance ....
Have not done any electrical test yet.... and I did not use any instruments on connectors.
My theories have been simply going by symptoms.
I don’t think it matters which lead you touch to connector ..... and I guess touch the other lead to a ground ?
Am I looking for 12 volts ?
I will be using The attached diagram of the face of the connector
Also....HAve a friend coming over to help tomorrow

 

That's correct.

On the 2 wires I listed above yes, to check the rest you would have to be backprobing the connector with it plugged in.
If you have a helper you can wiggle the connector while they watch the indicator lights and see if they flicker or light up.

 

I will let you know the results of these test.
Couple quick questions.....to back probe....you stick the volt meter lead along side the wire into the back of the connector and other lead to ground ...correct?.......don’t want to do any damage !!
Or should I pull glove box and check per your picture ? Or both .....Looks easier behind glovebox !!
Is there any other test I should try while I have a helper here....

 

I would use a small sewing needle or backprobe, other option is a wire piercing tool but if you do that make sure you seal the hole with nail polish or liquid tape.

You can but based on the symptoms and history we can assume what you will find at the connector behind the glovebox but you certainly can check it there.

You could temporarily jump pins 4 and 5 with a small piece of wire and see if the truck cranks.

 

Thanks for your help
What we found so far ...... when we jiggle wiring harness neutral light on dash flashes on and off ......
Park indicator never illuminates nor does 2 or L..... all others illuminate corresponding to position of gearshift .....pin 2 has 12v.... was unable to check further because voltmeter died !!
Also .... looks like no need for further testing because I think I need a all new wiring harness ..... do you know where I can find a part number ?

 

That’s going to be super expensive.

I’d opt for buying the connector and terminals.

I can probably find the connector and pin # for you if you want.

 

Of course I would rather just replace connector that would be the logical fix...but
Not sure it’s in the connector .....because I reached up on top of trans far as I could following harness with hand...and jiggled harness and neutral light was flickering ??? Wires near connector were not moving ???...,,,Harness has very little to no slack.
Do you remember or have Heard of any other post with similar circumstances ?


P.S. truck does go into neutral because we pushed it out of the garage into the driveway till I can decide what to do next ??????????????????

 

Oh. Ok.
That’s not an easy “fix”.
I’d at least find the bad area before ordering a harness. I mean, you are going to have to get/pull the harness anyways. Let me see if there are any other connections between that wire and the ECM. I’m not home right now. So it maybe awhile before I get a chance to look.

Just hate to see you spend all that money if we can “fix it ourselves”.

 

It doesn't look like there are any other connections between the P/N switch and the PB connector in the cab.
You're going to have to find the bad spot in the harness.

 

Just read post dated March 2023 by Joshua88 Who had similar problem and he went to Toyota and they told him they would have to remove the cab to replace that harness...... not an option !!
Unfortunately he did not post how he eventually repaired his truck or if he ever did ?
Any suggestions on how to proceed…....like how to narrow down which part of the harness is faulty???

 

DM93
“You could temporarily jump pins 4 and 5 with a small piece of wire and see if the truck cranks.”
Do you do this at the connector of the range sensor switch ?
It would be immensely helpful if I could get the truck started to move it around so I could fix it !!
The pins in/for that connector are the size of needles...... do you have any suggestions on what to use ?

 

If you just need to get the truck cranked just pop the STA relay out and put a jumper wire across pins 3 and 5 (the 2 larger pins) and the truck should start from the key.

 

Thanks for that information.....I will try it.....if it works it would be a tremendous help so I can move truck In and out of garage to do repair..... kinda cold outside this time of year in Ohio !!

 

I think if you are confident in approximately where the break is in the harness I'd try to get everything unhooked on that end of the harness and see about getting it fed out to an area where you can work on it.
I'm not sure how it's routed on an auto (mine is a manual) but I've done that quite a few times on other stuff when there's a problem in a harness and it's in a very inconvenient spot to fix

 

Thanks....can never have to many ideas or suggestions !
I think .....but not sure ....the break is on top of the transmission ?
Gotta vent a little... I’m a little pissed off about this ...this 07 truck with 68k miles
All be it 16 years old.
Has spent more than half of its life garage kept , never taken off road to speak of ,in my opinion
The wiring should not be failing !! I can understand sensors,but not wiring harness’s !!
Unfortunately...don’t have time this weekend to devote ...due to holidays !
Need to do a bit more investigation ....before I will decide on my plan of attack !! With not excluding possibly dropping the transmission to gain access ??
I will probably have more questions in the near future !! Lol
Hope you have a happy and safe holiday !!