GreyEnvy
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My truck is a 2001 M-1078 early A1 (no cut-off switch).
I have a knock-off version of the Cat ET3 code reader. It is unable to communicate with the vehicle ECM. The adapter cable appears to be bad. It consists of a J1939 Deutsch 9-pin connector on one end and an ODB-II style 16-pin connector on the other.
According to the late A1 electrical schematic I have, the J1939 pinout for connector X21 on page 20 is:
A: Ground -
B: 24V +
C: J1939 +
D: J1939 -
This is the standard J1939 pinout confirmed online, but there is also a Caterpillar non-standard J1939 connector that has the power and ground reversed with data on pins F & G. I measure 23V (engine off) on pin B, so it does not appear we are using the Cat version.
Pin C on my J1939 adapter cable does not have a path through to the OBD-II end. I have another J1939 plug I can splice in, but I need to know where pin C comes out on the OBD-II end.
This photo shows the truck X21 connector (top) with the bad ET3 adapter cable (bottom). I've labeled the pins (they're mirrored on the bottom because one plugs into the other):
This diagram shows where my pins exit the OBD-II connector:
Would someone compare their cable and, if you have the same OBD-II layout, let me know where pin C goes? I suspect this is not the same as a genuine Cat ET-3, but I could be wrong.
Thanks for any help you can provide!
I have a knock-off version of the Cat ET3 code reader. It is unable to communicate with the vehicle ECM. The adapter cable appears to be bad. It consists of a J1939 Deutsch 9-pin connector on one end and an ODB-II style 16-pin connector on the other.
According to the late A1 electrical schematic I have, the J1939 pinout for connector X21 on page 20 is:
A: Ground -
B: 24V +
C: J1939 +
D: J1939 -
This is the standard J1939 pinout confirmed online, but there is also a Caterpillar non-standard J1939 connector that has the power and ground reversed with data on pins F & G. I measure 23V (engine off) on pin B, so it does not appear we are using the Cat version.
Pin C on my J1939 adapter cable does not have a path through to the OBD-II end. I have another J1939 plug I can splice in, but I need to know where pin C comes out on the OBD-II end.
This photo shows the truck X21 connector (top) with the bad ET3 adapter cable (bottom). I've labeled the pins (they're mirrored on the bottom because one plugs into the other):
This diagram shows where my pins exit the OBD-II connector:
Would someone compare their cable and, if you have the same OBD-II layout, let me know where pin C goes? I suspect this is not the same as a genuine Cat ET-3, but I could be wrong.
Thanks for any help you can provide!
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