Not starting, lurches into gear
 

I have a 2015 GTS automatic 86 , the car only turns on after disconeccting and reconnecting the battery, I need to do this everytime I start, when I put the car into drive it jerks forward. I've had the car looked at by a Toyota dealership, 3 mechanics and 1 transmission specialist and none have been successful in identifying the issue. I was told it could be the inhibitor switch on the transmission. I replaced that, I was told it could be the transmission, I replaced that (yes the entire transmission) nothing has solved the problem. Im 99% sure it is an electrical issue. I came across an 86 repair manual with wiring diagram on starting system in the car. There is a rectangular module behind the glovebox where if I unplug the top connector for 10sec and reconnect the car starts, I need to do this for every start. Also while I am driving the abs, cel and traction light all come on.
So my question is, could this module be the cause of my problem, I ask this because it is 700$ and 6 weeks away in Japan so I don't want to get it and not have the issue solved.
Has anyone ever had such an issue?
I'm honestly so lost with this car and I really want to be able to fix this I don't want to have to sell it.

So many qs.....
Has the car been in any past wrecks ?
Have you tried more than one dealer ? Under warranty or just expired ?
Are your mechanics familiar with Frs Brz ?
What state are you in ?



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Why not pull that module that’s in the glove box from another 86 or Brz and see if it fixes rather buying , I’m sure if your close to anyone in this community they may be down to let your try for a beer or smoke out ʕ•̫͡•ʕ̫͡ʕ•͓͡•ʔ-̫͡-ʕ•̫͡•ʔ̫͡ʔ-̫͡-ʔ


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First off I live in Sydney Australia, I purchased the car wrecked in February 2019 at 30kms damage was to the passenger door, fender and airbags, I have since put on an additional 8000km on the car. Only one of the mechanics that saw the car were familiar with them, he works as a mechanic for a wrecker that specialises only in the twins. He said he's never heard of this issue before. I tried sourcing a used module from the wrecker but it seems I need a module with identical number. I am going to try a second Toyota dealer tomorrow

What trouble codes (if any) is the car giving you?

These are not in an particular order, the codes I get are different almost everytime I go to check them.
P0851 p0700 p0707 u0100 u0122

UGH! Those codes are above my pay grade - :(

I'll ring up ol @steve99 for you, to see if he has some ideas.

Id say the transmission park/nuetral switch is still faulty or incorrectly adjisted P0707 so the car doesnt see in in park or neutral then it wont start. You can ise toyota techstream to see the park neutral swich is operating correctly and being seen by the engine/ transmission ecu, also the wiring to park neutral switch mat be damaged causing it to appear faulty.


the other communication codes are likely due to you unpligging and plugging in stuff and interrupting communocations between cars control modules.


The transmission goes into a limp mode when it detects probpems with its sensors this likely causes the hard shifting.

I'm not sure if I mentioned this before but the gear indicator (P,R,N,D) does not show on my dash, and when I put the shifter into manual mode it just stays in drive. Do you think there could be something else causing this or could it also be due to the switch

Its possible that switch has multiple pisitions to indicate transmission selection

Right off the bat, when a transmission shifts into gear really hard, it's usually an indicator that the transmission is in fail safe mode. Is the module you are disconnecting the PCM? I dunno, maybe google the part number that's on it? You replaced the PNP switch... is it adjusted correctly? If it doesn't start in Park, does it start in Neutral? Whatever you're unplugging to let the car start, it's obviously seeing the issue again and returning to fail safe mode every time.

P0700, P0707 and P0851 are for the same issue, 700 is a generic code that trips in the PCM when the transmission requests the check engine light, 707 is the TCM seeing the PNP switch issue, 851 is the PCM seeing the TCM sending it the wrong PNP switch value. Ignore U0100 and U0122, they can be caused by the scan tool, I've created those codes myself and I've seen a toyota tech make them with his techstream and start on a wild goose chase looking for the wrong things. The PCM is also the one requesting all your traction/ESP lights, since it can't ascertain the state of the transmission for certain, all that stuff gets inhibited.

P0707 - Transmission Range Sensor "A" Circuit Low:

These DTCs indicate a problem with the park/neutral position switch assembly and the wire harness in the park/neutral position switch assembly circuit. The park/neutral position switch assembly detects the shift lever position and sends a signal to the TCM. For security, the park/neutral position switch assembly detects the shift lever position so that engine can be started only when the shift lever is in P or N. The park/neutral position switch assembly sends a signal to the TCM according to the shift position (P, R, N, D, or M). The TCM determines that there is a problem with the switch or related parts if it receives more than 1 position signal simultaneously. The TCM will turn on the MIL and store the DTC.

When an open or short circuit occurs, the contact points for all shift positions are set to OFF.


Malfunction status:
-All contacts for shift position P, R, N, and D are off
-Continues for 30 sec.

Yes I'm pretty sure the part I am disconnecting is the pcm, it's the rectangular shaped module behind my glovebox. Also I was told the switch was adjusted correctly (something about having a bolt and some points align). It does not start in neutral.
Also today I had the wiring that connects directly on the transmission and neutral switch swapped out to no avail.
You said it could be a problem at some point in the wiring of the pnp. Maybe I can try replacing the wires further down the line after the main transmission wiring.
I plugged the scanner again after swapping out the wiring and I got some new codes c1288, c1294 , p0974, and the p0700 code again but this time it says "automatic clutch system"
:sigh:

974 and 700 are a shift solenoid, those C codes are a module mismatch and subsequent function inhibition. Stop throwing parts at it. Just. Stop. Please. If at all possible return the car to the state it was in when it had just the PNP switch problem!

You "had" the wiring "swapped out"... I wish you could see how I'm clutching my forehead right now.

DO NOT replace wires wholesale on a whim.

DO find the exact thing to repair before taking any further action.

You could have easily tested the entire PNP circuit with a DVOM from the comfort of the passenger seat at the PCM without introducing unknown elements and without incurring further financial penalties... There likely was a single issue, now... now it's not as simple.

On a side note: Being told something is adjusted is not confirmation that something is adjusted. Even in a professional setting, if you bring me a car with a PNP DTC and tell me "it's been adjusted", you can be sure that I'll check the adjustment even faster and harder than if you tell me it's never been touched. I've seen what people do trying to fix cars and let me tell you, it's nasty.

:( It's just that I'm at such a point of desperation with the car I can't help but see that "brute forcing" my way to a solution is the only way I can fix this hence the swapping out of parts. You said I can test the pnp circuit with a dvom from the pcm, is there a handbook or some documentation that coukd show how I can go about doing this since I have a multimeter.
Also after seeing the swapping of the wiring didn't work I swapped back to my original wires and thats when the other codes came up.