Flickering dash lights and car won't start after new transmission installed

Hi all,

I had a broken transmission and I just finished installing a new (used) one.

Obviously it would have been too easy if the car will have start right away...

Before starting I plugged a small OBD2 to reset any code. As soon as I removed the scanner the lights on the dashboard started flashing, the fan turning on, and the car wouldn't start...

I unplugged the battery and plugged it back. same issue.

I checked the battery and it was at 12.25V so I will charge it overnight

Any idea?

Thanks a lot

Mazda 5 - 2006 - Automatic - 180K
 

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  • WhatsApp Video 2022-03-04 at 9.51.39 PM.mp4
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Last edited:
A few updates,

- The battery as fully recharged this morning but the problem is still the same.
- I only plugged the positive cable to the battery and connect a voltmeter from the negative cable to the negative of the battery. I got 12.8V which is think is not normal.
- I removed one by one the fuses to see if the voltage drop but nothing changed (the only one I didn't removed is the 80A EHPAS)

Not sure if what I'm doing make sense :ROFLMAO:

Any help with be really appreciate 🙏

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If you have 12.8v on the NEGATIVE cable terminal while disconnected, you have a short. But checking grounds is not a bad thing to do either.

I think you are working in the right direction, remove all fuses, inside and outside the car.

Disconnect the ECM. Disconnect the TCM. I believe the ECM is lighting up your dash because you have shorted it.

You should see no voltage between the negative wiring harness terminal and the negative battery terminal. Keep disconnecting things until you don't.
 
I'm not sure, the ECM and TCM may be one unit on this car. You really need the factory service manual for your car. I buy them as PDF downloads on ebay for like $10. They have diagrams and schematics, etc. Then there's no guessing.

If it were me, I'd pull ALL the fuses and ALL the relays. Next would be disconnecting plugs, etc. Something is shorting that negative cable to 12v.
 
Looking at a wiring diagram for 2013, there is a passenger fuse box that looks like it is under the kick panel or up under the glove box on the passenger side.

So you may have 2 fuse boxes to pull fuses from.

Since you replaced the transmission, I would really start there and look at all that, probably disconnect everything from the transmission. That new transmission may have an issue.
 
Hi,

So I have a few update:
- I disconnected all the connection on the transmission, stater, alternator etc + all the inside fuses...and it didn't change anything
- But I decided to remove all the fuses under the hood, again, and the ABS-V give me a hint, the power is dropping when I disconnected it (I thought it didn't change anything the first time I did it but I might missed that)

Not sure what the net step is. :unsure:

Thanks

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Weird. Next step would be to hook everything else up except for that ABS-V and see if the dash goes crazy again.
 
So I'm wondering if I don't have a spirit/ghost in this car...

I plugged back everything, also put back the ABS-V and ABS-P (both of them where dropping the voltage) as didn't really make sense...

- I tried to start to car and the car started...:love:...(but I heard a scratching/grinding noise from the engine/transmission so I stopped the car)
- I tried again..and the dashboard start flickering again...impossible to start...
- I removed the a few relays and fuses and by just removing the Glow Ig Key1 40Amp (not sure exactly what is it), the car stop flickering, but I couldn't start.
-I reinstall the Glow Ig Key1 40Amp and decided to plug my small OBD2 reader to look at any code...no code...and I have no idea why but when I have it plugged in, the dashboard is not flickering...and you know what, the car is able to start.........

No clue what's going on but if I leave the OBD2 reader plugged in I can start the car...

I installed a transmission from a Mazda 5 2005, mine is a 2006 model..the guy told me they are the same...not sure if that could play in something.

For the scratching/ grinding sound, it looks like the starter is not backing up completely and it stay in contact with the fly wheel. Not sure why but I will have a look tomorrow..
(I'm putting the video of the grinding sound in case it happens to someone one day..)
 

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  • WhatsApp Video 2022-03-11 at 9.28.34 PM.mp4
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So, I'm back on that issue, I have been quite demotivated to work on that as it feels endless but "never give up" right? :p

I still don't know what's going on but I realized the car is not starting because of the transmission position sensor....The car will start in neutral but not in park, and the P on the dashboard doesn't have the light.

Is there a way this sensor can be adjusted?
 
A lever is bent, a switch is out of position, the console is not seated properly, the transmission is not quite the same as the old one...could be anything between the shifter handle and the transmission.

Maybe there is an adjustment somewhere...but I have no idea.
 
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