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OBD diagnostics

Waydin_Stewart
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Waydin_Stewart

Waydin_Stewart

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Does anyone have any info about the pins on a 1998.5 OBD port and where the wires go. I.E. Where the chassis and signal ground go. Im trying to diagnose a faulty smarty cable or faulty obd/truck wiring. I have a 2002 ecu and a rebuilt 1998.5 ECU. I purchased a flash file from smarty to flash the 2002 to my 1998.5. IThe smarty would connect to the ECU while it was connected to the 2002 donor truck. IT wont on my truck. It wont connect to the 1998.5 or 2002 ecu while on my truck. I can hook my scan tool up to my truck and it will connect to both and read codes on both? SOOOOO I think something might be wrong with my obd port.

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Chris O.

Chris O.

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SCI - Serial Communication Interface
SCI consists of:
– Dedicated point-to-point, dual-wire, nonmultiplexed
serial communication interface
– Supports both diagnostics and flash reprogramming
capability
– Supports multiple baud rates to accommodate
both the low-speed diagnostic command mode
(at 7812.5 bps) and the high-speed parameter
interrogation command mode (at 62,500K bps)

• With the key ON:
• No scan tool connected to the DLC; there should be 5 volts
at the Rx circuit.
• No scan tool connected to the DLC; there should be no
voltage at the Tx circuit.
• The scan tool connected to the DLC; there should be 12
volts* at the Tx circuit.
• The scan tool connected to the DLC and Engine selected
from the Select System menu; there should be 5 volts at the
Tx circuit.


* This is the default voltage for ISO-K. When the Engine is
selected from the Select System menu the tool will turn off the 12 volts
and apply 5 volts to attempt SCI communication

 

Flash Programming:
•Scan tool pulls voltage down when sending Data on Rx
•Scan tool raises voltage on Rx circuit to 20 volts (indicates flash)
•Module sends message back for error detection

Edited by Chris O.
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Waydin_Stewart

Waydin_Stewart

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what are the rx and tx circuits? So I was correct on the smarty does use the sci transmit and sci receive wires to flash the computer. So I can hook a normal scan tool to the truck and it will read data and clear codes. I cannot hook the smarty to it and read codes or flash the computer. So My sci wires will support low rate but not high rate programming. how do i go about diagnosing this?

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