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M48 --> LS7 --> Crank Sensor --> Data Cable

 
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alohajeff



Joined: 05 Jun 2012
Posts: 1

PostPosted: Tue Jun 05, 2012 11:58 pm    Post subject: M48 --> LS7 --> Crank Sensor --> Data Cable Reply with quote

I am assisting a buddy with a project. He is running an M48 on an LS7 with the factory GM crank sensor. I have been searching the Internet for answers and think that the M48 might not have the correct Mode settings for the crank sensor used on the LS7. That's the first problem.

The bigger problem is we are unable to access the ECU using the Motec 6.20 software. We are getting the ECU NOT CONNECTED message. I understand that the M48 ECU is outputting TTL at the DB9 plug and not RS232. I purchased a TTL --> RS232 converter. I disassembled the Motec plug on the ECU side and found 5 wires. From what I can gather Pin 1 is +5v, Pin 5 is RX, Pin 6 is GND, and Pin 9 is TX. Searching this very site I found a post stating that we only need 3 of those wires... GND / TX / RX. I have built a cable that gets the Pins from the M48 DB9 to the TTL / RS232 adapter. Unfortunately after testing it tonight we are still unable to connect to the ECU. I am using an older IBM Laptop with a true RS-232 serial port. I also tried my USB/RS-232 adapter with no luck. The frustrating part is if my information is correct this should be working just fine. I have ZERO experience with Motec systems so I am looking for someone that has successfully built their own TTL --> RS-232 cable. If you prefer to PM me that would be great. I'd like to ask a few basic questions to make sure I'm on the right track. We are stuck until we can open communications with the ECU.

Thank you!

Jeff
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TurboNova



Joined: 08 Dec 2004
Posts: 1158
Location: Lake Havasu City, AZ

PostPosted: Thu Jun 07, 2012 12:37 am    Post subject: Reply with quote

I built myself a cable using the Accel gen 6 cable that I had, it worked but not quite right. I gave up and bought a M48 cable after that.

The M48 is limited and I had issues with the 60-2 trigger and 8 coils. We ended up using a 12 magnet crank trigger to make it work. Make sure you get the denso coil modification to your ignition expander or the coils will over dwell and the engine will start very hard like the timing is advanced too much.
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Brian Macy
TheEFIStore.com
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