94 explorer xlt

[chunk9226]

my check engine light keeps comming on after the truck has been runign for about 20 min and i have a code reader and it keeps comming back as systems all clear. so could it be a sending unit?

 

[arco777]

Usually the CEL indicates a code and then stores it, and even without a CEL codes can still be stored. I'd lean towards a failure of your scanner or (I know it sounds dumb but it happens) possibly scanning at the ABS test plug instead of the diagnostic connector. Try pulling codes manually by grounding the input connector and reading them through CEL flashes; the link below shows how and lists code meanings. The connector you're looking for is usually on the passenger side near the firewall.

http://www.fordfuelinjection.com/?p=13

 

[chunk9226]

Usually the CEL indicates a code and then stores it, and even without a CEL codes can still be stored. I'd lean towards a failure of your scanner or (I know it sounds dumb but it happens) possibly scanning at the ABS test plug instead of the diagnostic connector. Try pulling codes manually by grounding the input connector and reading them through CEL flashes; the link below shows how and lists code meanings. The connector you're looking for is usually on the passenger side near the firewall.

http://www.fordfuelinjection.com/?p=13

yes we did that and my buddys dad came over and looked at it to(he works a ford dealer ship) and got the same code.

 

[MrShorty]

Yes it could be any number of sensors or actuators or wires. Without a code, it's a shot in the dark.

I would wonder why it won't store the code. You might check the KAM power wire (pin 1 I think), to make sure the PCM has power to its memory with the key off. Check the grounds to make sure the PCM's grounds are good (It's not unheard of for them to corrode where they connect to the battery cable).

Any other symptoms?

 

[chunk9226]

i am have having a problem with my low range could that be what is setting off the check engine light

 

[MrShorty]

I'm not certain if it changed for '94 (don't expect it did), but my '92 doesn't have a direct connection between the PCM and the transfer case. However, something like the Vehicle Speed Sensor (VSS) is connected to both the PCM and the transfer case shift module. Transfer case shifting issues are most often shift motor issues, so it doesn't seem likely that a VSS problem would be the case here, but, as a stab in the dark, it's something. Do you also have troubles with the cruise control (also tied into the VSS)? Does the transmission shift into 4th gear (electronically controlled using VSS as a principle input)?

Another "shot in the dark": are you sure you are waiting for the CM codes to come out? It occurred to me that someone unfamiliar with the test procedure might see the first KOEO 111 and think he was done and interrupt the test before the CM codes are even output (which would clear the CM codes, BTW). From your original post, I assumed you meant you are seeing four 111's [111 111 (KOEO codes) 1 (separator pulse) 111 111 (CM codes)], any chance I have assumed incorrectly?

Another "long shot" "stab in the dark": is there possibly a loose connection in the jumper wire you are using (or other test equipment), that would somehow interrupt the test and cause it to clear CM?

Have you tried the KOER test to see if it reports the problem there (where there isn't a question of "storing" the code)?