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Discussion Starter #1
Hi All,

I'm an mr2 owner from Miami, FL and I own a 2004 mr2. Unfortunately, it's been parked for over a year because of an smt issue. Initially when the car broke down I took it to the dealer and they told me that the Alternator was the problem. Since I have a hard time trusting dealers my brother and I took out the part and took it in to Advance auto parts and ran a diagnotic on the part and they told me there was no problem with it. Eventually our own reader gave us the P1646 code.

Let me backtrack and say that when the car started having problems it was when shifting gears. One day the car downshifted on its own and never came back After fiddling with it some more and reading tons of posts I eventually ponied up the $$ to buy the new TCU. i installed it yesterday and the car cranked up but it's still not reading any gears. I read somewhere about the PUMP PRIMER and I've noticed that mine keeps running. When working on my car yesterday, it stayed on for almost a minute after turning off my car. Anyone have any ideas? I'm losing my mind over here
mireyamedina Posts: 1Joined: Sun Nov 13, 2011 8:09 amLocation: Miami, FL USA

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Welcome to Spyder Chat..

Sorry About your Woes..

Some good Some Bad.. Glad you got a New TCU.. as the Software Has Changed.. ( Check the Labels.. and Note the Differences.. ) Newer Version TCU are not as QWERKY as the Old Ones..

Sounds like you have a HPU ( Hydraulic Power Unit ) that is Low or Out of Fluid..

Remove the Air Box, and Check the Fluid Level on the HPU to see where it's at..

See this Post for Someone dealing with the Same thing right now..
http://spyderchat.com/forums/showthread.php?49262-SMT-problem-(warning-flash-light-out-after-few-minutes-driving)-HELP!


And YES I would trust the Recommendation of DOT 4 Brake Fluid..

Cap
 

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I'll try to get started...pump running for more than 30seconds meansthe hydraulic pressure is not building properly. Maybe low fluid or a worn hpu pump. Tribal knowledge says the tcu computer is never the problem. Did you keep your old one?

Edit: listen to Cap above...
 

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Been thinking about your Situation Further..

The 'Problem' you have Now, is you have a New TCU in a Car that it has never seen.. For that TCU to Stay in the Car, you will need to Perform a 'Sensor Re-learn'..

There is a Toyota Software Program available that will Perform that Function for you.. And Copies are Floating around that can be had.. Or you can Get the Car to Trigger one for you.. But it is still a Pain in the Ass to do..

My Advice is to put the Original TCU back in.. I know it's a Giant Step backwards.. BUT.. that TCU already knows your car.. and from that Starting Point, we can Troubleshoot the First Problem that Started all of this..

Then after the Car is Running Fine.. and if the Software is Different Between the TCU's, then you can Swap the TCU's and Perform the Relearn Procedure..

Cap
 

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Discussion Starter #5
Here's where I am so far

Hey Cap Weir and Cyclehead, thanks for getting back to me so quickly, sorry it took a bit to get back but I couldn't even get back to work on the car until this weekend. Anyhow, I re-installed the old computer after unhooking all the wires from the ECU as well and cleaning them off. Car cranked up and I took it around the block. Car went into 1,2,3, even 4 then when I tried to downshift manually and the car wouldn't respond. I braked slowly and it went down to first then I couldn't get it back up to second. I got down the street and tried to put the car in reverse and nothing. I decided to check on the SMT fluid and I took a photo of the SMT fluid container for you guys to view. Cyclehead, I think you're right on about the fluid being too low. I'm not sure what the mark should be but I checked out the posts that Cap Weir referred me to and I think I'm well below the fill line. I'm posting two pics and If you notice the shadow of the fluid is way low. Or at least it looks that way to me
My next step is to try filling it but I'm a bit hesitant about the Brake Fluid in place of the Toyota SMT fluid...I'm tired of spending any more money but I also don't want to do something that may ruin my car...have either of you used the DOT Brake Fluid?

Thanks again MR2 friends!!!


 

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I've been using it for around 4k miles now with no problems. Actually sounds like you have a sticking/shorted switch. If the last time you shifted up it got stuck in the pressed position or shorted to the pressed state it won't take further commands until it gets out of the "pressed". You can tell the difference between the switch/button screwing up and the hpu by if you hear a repetitive clicking about twice a second while it refuses to move along with the hpu motor continually running. The fact that it downshifted on its own makes me think button error. Whichever way you you used to upshift to fourth before it would not take any further commands is probably the culprit (console shifter or steering wheel buttons.) More than likely the console since it likes to attract spilled soft drinks.
 

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Discussion Starter #7
hmmm

No clicking really happening and no spilled soft drinks, lol. I pretty much always use the shifter not the steering wheel buttons. It just goes blank while engine is running perfect.
 

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No clicking really happening and no spilled soft drinks, lol. I pretty much always use the shifter not the steering wheel buttons. It just goes blank while engine is running perfect.
Ah, I thought the TCU swap fixed the blank lcd, I'm sorry.

Are you getting the p1646 on both TCU's then?

P1646 without U0001 on both could at best be a grounding failure, at worst ECU replacement. The p1646 circuit is looped through the casing of the TCU and into the chassis (pretty sure they meant chassis ground,they used earth ground? on the schematic) as the U0001 is looped through wire back to the ECU. Check your grounding on both the units and make sure the loop isn't being interrupted by corrosion on the fasteners. A weak power supply (battery/alternator) will cause this too as it won't have enough amperage to make it through the chassis.

A note to Cap, actually seeing the circuit for the first time, it kind of appalled me. Shooting such an important signal at a casing ground is just horrible engineering. It was like they put it in as a backup of the U0001 circuit in case it failed, then coded it as a parallel reliant circuit. There's absolutely no overvoltage protection, and only a single transistor in place for reverse flow. Looks like I'm going to be insulating my tcu and adding a fuse or small circuit breaker on the ground side, it makes no sense to have no protection on a device this expensive. What's really funny is they specify shielded cable on a chassis ground, that's like shaving a cat before you throw it in a microwave so its hair doesn't catch fire and it burn to death.
 
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