Unable to Read Engine Codes

[cgraves]

I have a 1994 XLT 170,000 miles, very rough idle and miss at all speeds. I have been unable to pull any engine codes. My scanner says unable to connect. Any thoughts would be appreciated.

 

[Tbars4]

..Try this and put your location under your name...
http://www.explorerforum.com/forums/showthread.php?t=255962

 

[Joe Dirt]

You probably don't have an OBDI scanner...

Use that paperclip method...

 

[cgraves]

I have tried the paper clip method and with no response from the check engine light. Is there a fues problem or do I have a computer problem.

 

[MrShorty]

Those are possibilities. Though, if it was a fuse problem, it would be the main EEC fuse, and the truck wouldn't run at all. A faulty circuit inside the PCM is also a possibility. Other possibilities:

There's a break in the wiring between the self-test connector and the PCM.

Or maybe between the PCM and the CEL (does the light ever come on KOEO, like just before starting?) or the CEL bulb is burned out. If you look in BrooklynBay's code list thread (EEC-IV forum), he has a diagram that shows how to hook up a test light or voltmeter at the self-test connector that can be used to flash out the codes.

Are you certain you are getting good contact with your jumper wire at the test connectors? Does the PCM show any signs of entering self-test mode (do the relays click when you hook up the jumper wire?)?

 

[cgraves]

I have checked my connections and alos tried using a light in the diagnostic socket. When I turn the key on the light comes on and stays on, I get no flashes.

 

[Joe Dirt]

When you turn the key on, does the CEL light come on at all? I've seen people remove them before a sale, or it could be blown out...

 

[MrShorty]

I have checked my connections and alos tried using a light in the diagnostic socket. When I turn the key on the light comes on and stays on, I get no flashes.

Assuming the light is hooked up correctly, that suggests to me that the PCM isn't entering self-test mode. Make sure to check the STI (self-test input) to SIG RETurn jumper connection and the accompanying wiring between the connector and the PCM for bad connections.