Connecting to computer on the bench but not in the car - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 12-22-2013, 01:57 AM   #1
Junior Member
Thread Starter
 
Join Date: Oct 2013
Location: Yokohama
Posts: 49
Total Cats: 2
Default Connecting to computer on the bench but not in the car

I have built an MS3 + MS3X ECU for my JDM 1.6 1992 MX5 (Eunos Roadster) following Frank's guide: http://westfieldmx5.devocht.com/megasquirt/ms3/90-97-ms3/

On the bench using a car battery I have connected to the laptop and flashed the ECU with the newest firmware.
Tuner Studio also communicates with the ECU on the bench.

The problem is when I hook it up in the car the computer doesn't communicate with it. It detects something on the USB but doesn't connect to Tuner Studio.

The car runs fine on the stock ECU and I read 11.5v between the 12v and Ground. I don't see why the MS3 doesn't seem to be powering up on this.

I'd really appreciate your advice.
Rothko is offline   Reply With Quote
Old 12-22-2013, 10:18 AM   #2
Senior Member
 
Join Date: Aug 2010
Location: Arl. Texas
Posts: 937
Total Cats: 23
Default

Are you using the same cable to hook it up both times? It seems that a lot of connection problems come from the usb cable and or the drivers for the cable. It should be cheap and simple to swap another cable just to rule it out.
Miater is offline   Reply With Quote
Old 12-22-2013, 10:53 AM   #3
Elite Member
iTrader: (21)
 
Join Date: Jun 2007
Location: Rochester, NY
Posts: 5,684
Total Cats: 555
Default

How are you grounding it when on the bench vs. when it's in the car? A vast majority of electrical problems in cars has to do with grounding.

If it's through the cable, then swapping as Miater suggested is an excellent place to start.
rleete is offline   Reply With Quote
Old 12-22-2013, 11:55 AM   #4
Junior Member
Thread Starter
 
Join Date: Oct 2013
Location: Yokohama
Posts: 49
Total Cats: 2
Default

I'm using the same USB cable all the time.

I can set it up in the passenger foot-well using the stock harness and get no signal to TS. Then take laptop, cable and ECU to the boot of the car and hook it up directly to the battery and get a signal in TS.
Rothko is offline   Reply With Quote
Old 12-23-2013, 05:02 AM   #5
Junior Member
Thread Starter
 
Join Date: Oct 2013
Location: Yokohama
Posts: 49
Total Cats: 2
Default

Thanks for the input - I checked the grounds but didn't find a problem so tried a few other things.

After a lot of messing about I found that when plugged into the car, the MS3 only communicates with Tuner Studio when the TPS is not connected.

Now, Frank's method says that the stock TPS would cause a floating input but I didn't expect it to prevent the MS3 from communicating with TS...

Anyway, hoping it was a problem with the TPS and not something inside the MS3, I tried the BMW TPS and I got some sensible readings in TS. On the back of this I installed the BMW TPS and calibrated it just fine in TS.

If you have any idea why the stock TPS would prevent the MS3 from communicating with TS I would be interested to know.

I hope this will help some other newbie in the future!!
Rothko is offline   Reply With Quote
Old 12-27-2013, 03:54 PM   #6
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

When you hook up the stock TPS, you're shorting VREF to ground and shutting down the processor. There is no reason to wire the MegaSquirt to the stock 1.6 TPS; it's not really a position sensor, just an on/off switch.
Ben is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
NEW-Wiseco Piston, K1 Rods, Supertech Valves & Spring/Retainer, TB&C pedals Rudes333 Miata parts for sale/trade 17 11-05-2015 02:16 PM
Software/IT types/Joe P, step inside please z31maniac Insert BS here 13 09-22-2015 03:59 PM
Help multi issues here! ReallyRottenTurbo MEGAsquirt 4 09-22-2015 01:49 PM
1997 Miata Misty_Miata pineda92 Meet and Greet 4 09-20-2015 10:22 PM
Help installing DDM HID kit thumpetto007 General Miata Chat 8 09-04-2015 06:25 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 11:48 PM.