I've been chasing down a problem where my 95 will not scan.
I have posted about it before, but because it is that wacky 95 OBD-I.5
everyone has always assumed it was the scanner or scanner connection.
Well I have had a shop try and talked with Autoxray and it appears there
is really a wiring problem in the car, and not my scanner setup.

So I've been diligently reading the FSM and trying to trace the circuit between
the DLC and the PCM. It is circuit 800 with tan wires to the white PCM harness connector.
The circuit goes to the DLC, HVAC, TCM, and PCM,(and some others).
Anyway in one section of the FSM it says that a fault in this circuit will result in "No Scan Data" and "Traction Control Off".

Guess what? My traction control module is dead, has been for a while, and the
indicator is showing on the dash.

Would the Traction Control Module cause issues in this circuit that would not allow
a scanner to connect to the PCM?

If I'm reading this correctly the FSM says the wire goes through several modules
from the DLC to the PCM. It seems each module must be checked or bypassed to check
the continuity of the circuit. Is that right?

I will try to disconnect and jump some wires this weekend (IF IT'S WARMER OUT).
I'm not that good at electrical issues, Ohms, volts, resistance, etc. but I do own
an nice multimeter.

Can somebody shed some more light on the possibilities here?

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Black 95 SSEi (original owner) 238K miles
Black 05 GXP (some idiot put the first 12K on it)186K miles
Black 04 Tahoe (original owner)310K miles
Black 16 Traverse (original owner)90K miles
Black 15 Lacrosse (some nice lady put first 15K on it)43K miles


"You can have one in any color as long as it's black" - H. Ford

That is called a daisy chain. It is frequently used on the modules that the pcm and DLC both see.

One method to get around it temporarily would be to run wiring directly from the pcm pins to the DLC and then put a seperate switch coming off those wires to the remainder of the daisy chain. This should allow you access to scan the pcm, however your main issue of where the connection error may be located would still exist.

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97 Ei
97 GS
98 GS