Z32 Auto Transmission Troubles

Discussion in 'Technical' started by Doug, Dec 9, 2020.

  1. Doug

    Doug New Member

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    Hi, I'm new to this so here goes. My ride, a 1990 300zx Japanese import, auto, non turbo. A nice machine almost completely stock since I broke both the front mags They couldn't handle the aggressive steering angles the Z puts out cornering and I ended up with stress fractures in both of them. OK, my problem, the auto went into hold mode without permission and for no apparent reason. I have a power hold switch, I don't have an AT light on the dash ( really it isn't there), Check engine light says code 55, all ok. Tracing the wiring from this power hold switch is all but impossible, I can't find it on any of the wiring diagrams, so other than lights on the dash where else does it go, what else does it do ???
    In the end I hope its just a connector needs cleaning or wiggling but knowledge is power !!!
    All help gratefully accepted. :)

    Doug
     
  2. ivan129

    ivan129 Member

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    Have you tried disconnecting the switch incase its gone faulty?
     
  3. Doug

    Doug New Member

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    Yes, pulled it apart, cleaned it, It's working as it should, the power dash light came on when I was road testing it and switched it on then , it never come back on . hold dash light works as it should, this is why I think its a faulty connector somewhere. I will pull the bulb and check it but I don't that would put the tranny into hold mode. I've got the auto CPU unplugged so that I can check pin continuity, but its a learning curve for sure
     
  4. ADAMZX

    ADAMZX 2000spec Conversion

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    Hold on what are your transmission symptons if any or is it just showing the hold light in the dash? and so you assume its in hold.

    I ask this because the hold switch doesnt function the way you might think it means for our cars like holds that gear. No the hold functions changes the way the transmission shifts at what speed your going. Much like the power. The hold switch however makes the transmission shift from 1st gear up to 4th gear very quickly and also takes away hard acceleration and as i can only describe as going from a v6 engine down to a 4cyl engine in this mode. I think its a fuel ecomony setting basically.
     
  5. Doug

    Doug New Member

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    The transmission went into a holding mode when I was just driving around the suburb. As I understand it, that mode is for slippery roads ( ice snow) and stops power being delivered to the back wheels reducing wheel spin. When your gearbox starts doing strange things, the last thin I do is stomp on the gas to see what I can break. This is why I think its an electrical fault, the gearbox normally works like a dream. Finding wiring diagrams that show how everything is connected together especially this switch isn't easy. Another thought is that the box has gone into a limp home mode, does it have one?? I've bought the Nissan consult plug and free software but It only shows engine diagnostics, the full version including transmission is another 100 euro. I can take it to a Nissan specialist but their ability to find the problem will cost thousands to fix isn't where I'm going just yet.. Anyone know if ECU Talk is any good ?? will it do the tranny??
    Doug
     
  6. ADAMZX

    ADAMZX 2000spec Conversion

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    Yup your 100% correct about the hold mode abd what its designed for. I have been through a bit of trans problems with my z and it took me 2 trans to figure out that the real problem was the auto trans ecus / modules and them going bad after 20 - 30 years. I replaced it with a second hand module and the problem was solved over night. I suspected the same switch as you do but the same problem still continued even when the connector was disconnected. The trans codes on conzult can somewhat help you but in my case completely useless as it was the ecu that was faulty not the box itself. Just thought id suggest maybe your ecu is the fault.
     
  7. Doug

    Doug New Member

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    OK, thanks , a new anything at this stage is at the other end of my thoughts, I'll hit and wiggle a few more things first. Anyone know anything about a dropping resistor ????? :)
     

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