Another problem. P0705 code, reverse gauge light when braking

So the girlfriend went shopping today, called me to say the check engine light is on and the gear display on the dash is going wonky. Nothing strange leading up to it, and the truck is running fine.

I plugged in my OBDII scanner with Torque when she got home. Sure enough, P0705 code came up, the check engine light is still on, and the really fucked up part...whenever I touch the brake, the 'R' (reverse) light on the gear selection on the dash lights up and flickers a bit, no matter if I'm in Park, Drive or anything else. The reverse lights at the back of the truck light up as well as the brake lights too, and it looked like they were flickering.

It's pretty cold up here, there's no standing water anywhere and it was a clear day. The truck hasn't seen any water crossings or anything, so I can't imagine its a recent corrosion issue. I disconnected the battery for a few minutes, reconnected and fired it back up - same deal. No more check engine light after I cleared the code via Torque, but the same issue is still there - the reverse light and lamps are going on any time I touch the brake, and I imagine it'll throw a code shortly.

Any idea WTF is going on, any remedies (short of going to the dealer...which is over 400 miles away)?

 

• Short in the taillight housing, allowing parking light or brake light voltage to backfeed into the reverse light housing.
• Short in transmission position switch on side of transmission
• cluster problem (internal)

Just a few ideas.

 

What year and engine ? is it 4x4 ?
P0705 code popped on yesterday rondog 2nd Gen. Tacomas 75 12-20-2014 02:45 PM Code P0705 = BAD NEWS!!!! MadeInMaine Technical Chat 13 05-26-2014 05:44 PM Backup Camera Mod & P0705 error code jeffhorton 2nd Gen. Tacomas 1 10-05-2013 11:06 PM Trouble code P0705- will dealer help? Zizo 2nd Gen. Tacomas 26 07-01-2013 12:43 PM HELP!! just threw a code P0705 MadeInMaine Technical Chat 2 01-18-2011 03:11 PM

 

Awesome, thanks, I guess I'll start with the tail light housing.

Sorry. 2007 4x4 V6. Seems to otherwise be shifting and driving fine, no delayed or hard shifts.

 

Did you find a solution to this waffles? I'm having the exact same issue and am about to pull my hair out trying to find the issue. I took out both tail light assembly and everything looked good there. I even pulled the Park Nuetral switch and sprayed the contacts with electric cleaner and put everything back and that wasn't it either.

I did trace the wires back and found a ground (see picture). It's located behind the driver's side tire and strut on the frame. I accidently broke the bolt head off trying to loosen it, but I cleaned the contact and frame good enough for a good contact....well that didn't work either. Are there other grounds further toward the front of the Tacoma? I looked at the passenger side at the same Iocation but there wasn't a ground there. I ran out of time and patience to keep looking at it tonight so I decided to turn to trusty Tacomaworld.

I'm starting to get pretty frustrated with this as you can see from my handle I'm an accountant and not a mechanic or electrician by any stretch of the means. So any help would be greatly appreciated.

By the way, it took me forever but I found that the ground wire for the tail lights are the white wire with black stripes. In case anyone else in the future has this issue.

My Tacoma is a 2008 dbl cab, 4.0 V6, 4*4.

 

Bump

 

Bump 2.0

 

Bump 3.0

 

I'll bite.

IF the gear shift display is indicating incorrectly you have an issue with the Park Neutral Safety Switch on the side of the transmission.

This switch controls the indicator and also signals the ECU what gear you have selected.

It is definitely in need of replacement.

See here: http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0260013.pdf


It says Trouble Areas:

• Open or short in park/neutral position switch circuit
• Park/neutral position switch
•ECM

 

Thanks Jimmy. I just replaced the PN safety switch this past fall with an aftermarket one...really frustrating to have to be replacing it again already.

 

I'll bite.

IF the gear shift display is indicating incorrectly you have an issue with the Park Neutral Safety Switch on the side of the transmission.

This switch controls the indicator and also signals the ECU what gear you have selected.

It is definitely in need of replacement.

See here: http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0260013.pdf


It says Trouble Areas:

• Open or short in park/neutral position switch circuit
• Park/neutral position switch
•ECM

 

Just to give an update on this....

I pulled the Park Neutral Safety Switch (PNSS) off and cleaned the electrical contacts with electrical cleaner and put it back on. I started the truck up and had the same issue; the Reverse Light would come on when I hit the brakes. I left it be for a day or two, came back out to start it up and the problem was gone!! Drove it around that day but had another issue pop up. Sometimes the truck wouldn't start. It was evident the battery wasn't dead and when I would turn the key absolutely nothing happened. I think this is a built in safety feature when the PNSS isn't fully connected, but I didn't know that at the time. Eventually I got the truck started after turning the key a dozen times and was back on my way.

Got home and really tried to squeeze the electrical connector onto the PNSS as tightly as I could and that solved the starting issue. However, the very next day I went to take the truck to church and now my original problem that happened in the fall of 2018 that caused me to replace the PNSS to begin with popped back up. My reverse lights were always on no matter what gear I was in, but only when my headlights were on. So weird...

Thankfully I kept the emails/receipts from my October 2018 order of a replacement PNSS from CarParts.com (JC Whitney) because the part came with a 1-year warranty. Called CarParts.com and I reached an actual human being right out the gate with no wait time. They were really friendly and got my replacement part ordered and ready to be sent out within the next 48 hours. Even gave me a prepaid label to send the defective part back with. I was very satisfied with CarParts.com which was a pleasant surprise. I figured I was going to have to fight tooth and nail to get a replacement part since that has been my experience with all other car part websites. Highly recommend them and I will be ordering parts through them in the future.

I'll keep this thread updated once I get the replacement part put on and tested.

 

I FINALLY FIGURED IT OUT!!!!!!!

As I was researching I was finding a little info here and a little info there so I'm going to put everything I tried and used in this post that hasn't already been covered.

Just to review, the issue I have been having is that the reverse or back up lights would come on and stay on when the parking and/or headlights were on.

I received my replacement NSS (or PNSS) switch from CarParts.com, placed the new one on and still had the same issue. I even zip-tied the wiring connector to the NSS switch to make sure it was fully connected and still no luck.

I then turned to the wiring harness connector located in the junction box under the dash and to the left on the driver's side (see picture). Here is a write up of how to remove the plastics to get to the junction box. I sprayed not just the connector that was referenced in the picture but all of them with electrical contact cleaner. Still no luck.



At this point I was getting pretty fed up with it and finally just took the reverse light bulbs out so I could still drive it after dark without getting pulled over.

A few weeks pass and I decided to do some more research so I broadened my search to not just Tacoma's but any Truck with the same issue. I came across a Chevy message board where an older truck was having the same issues even after the guy re-wired everything. Turns out he got some wires flipped in the....get this.....7 pin trailer harness!

I got home that night and looked at my wiring harness (I had an aftermarket one because the OEM broke) and to my surprise the back cover had broke open and mud, snow, dirt, rain had been thrown in there for some time. I live on 2 miles of gravel so I can only imagine the abuse it took. Anyways, I looked at the wiring and it was ate up with a few of them not even connected anymore, just dangling there.... The screws in the wiring harness were rusted and one was missing a screw (see below). Also, as you can see the bolts that held the connector to the frame were so rusted they just snapped off.



Ordered a new harness (

$33 Hopkins Towing Solutions 48470 Endurance Multi-Tow 7 Blade, 5 and 4 Flat Vehicle Side Connector

Hopkins 48470) and put it on last night and everything is working as it should now with the Check Engine Light gone!! I put a ton of dielectric grease on all the connections and taped the snot out of the back cover along with zip ties so hopefully this never happens again.

So if you are facing the same issue as I was check your 7 pin connector.

Below is the 7 pin wiring diagram I followed for my 2008, which I tested and works;

Black - Auxiliary (12v)
Brown - Right Turn
Blue - Electric Brake
Yellow - Reverse/Backup
White - Ground
Red - Left Turn
Green - Taillight

If you do end up going with the Hopkins 48470 below is the wiring for it;




Hopefully this helps someone else out there that may be having the same issues and frustrations as I was!

 

Dang!

 

Good job.