Computer information port

ERROL H

MEMBER
1992 GMC C3500
7.4L
V8
4WD
AUTOMATIC
157,000 MILES

The assembly line data link won't give me any information when I plug in the obd1 it only informs me that no information is available from the ecm (computer). The service engine light is on and I can't scan the engine to detect where the fault lies. Also my transmission is electronically controlled and stays in second gear without shifting into drive. I just installed a new computer with no change in the system. How can I scan the engine or get power to the scanner plug under the dash. If a bad ground is the problem can I run a new ground wire to the computer and if so which of the terminals are the ground terminals. Are there schematics available that outline the wiring diagram of the plugs?

8 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

Have you tried jumping the obd1 connector to see if you can flash the codes out of the check engine light? That would be a good way to see if there is a issue with the data lines.

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Thursday, November 21st, 2013 AT 8:43 PM

ERROL H

MEMBER
7 POSTS

I've tried jumping the data link connector and no change, that would mean that there is a problem with the data lines. What would be the next step to take to try and correct the problem? Once I can receive the codes I can begin to change the defective part or parts to get the engine running right. Your help in trying to correct the problem is greatly appreciated. Thanks again.

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Friday, November 22nd, 2013 AT 7:54 AM

SATURNTECH9

MECHANIC
30,869 POSTS

I posted the trouble tree for the check engine light not flashing when jumped.I posted the connector on the wire diagram to show you which color wire goes to what letter pin on the obd1 connector.

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Friday, November 22nd, 2013 AT 11:51 AM

MAXIMILIAM

ADMIN
436 POSTS

I finally found out why the data link isn't responding. After checking the entire electrical system including load testing I was running out of options and it was down to the eprom so I phoned the dealer and found out that the epron was out of a 1995 not 1992.

The dealer informed me that the part is obsolete and that the replacement part requires the original part # for comparison. Of course I don't have the original part # and am again at a loss of what to do. I am going to try and retrieve the original info. From the dealer. I have a 1992 F3500 454 4x4 dually with a 4 speed automatic tranny.

Errol H

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Saturday, November 23rd, 2013 AT 1:18 AM

ERROL H

MEMBER
7 POSTS

I found a eprom from a 91 454, plugged it in and the service engine light went off, Took the truck for a ride and the transmission shifted properly. The wrong eprom chip was the culprit. I am curious as to whether the proper chio may be different in some small way than the one I found?