On board diagnostics.

[92exp4x4]

My 93 4.0 van has had an intermittent CEL and pinging under load since I got it. It seems the engine burns about as much trans fluid as gasoline, which is probably part of the pinging issue. Anyway, I hooked up my scan tool this past sunday night and could not get any of the tests to work. The KOEO test never completed and the KOER test finally timed out and gave me a "no communication" error message.

I cleaned the connections, and inspected the plug.. only a tiny bit of corrosion on one of the pins. I tried it with the STO connector plugged in and not plugged in to the tool. I'm really not sure why its not working. Its not like the harness has been fooled with. This van is about as undisturbed as it gets. I feel like no one has worked on this thing at all over the years. No broken connectors, brackets, wire looms, etc, just lots of rust in the body. I haven't had time yet to test my scanner on another OBD1 vehicle, probably doing that tomorrow. I have not tried the paperclip method of retrieving codes yet either. The OBD2 function works great, just used it twice today, so I doubt the tool is defective.

Does anyone know about a fuse or common connection issue that could be causing this? I really haven't had a whole lot of time to mess with this yet, just hoping there could be a simple solution I'm overlooking. I was hoping to verify my lack of overdrive function and maybe a lean/rich code from the trans fluid ingestion (modulator).

 

[Josh P]

No fuse that I know of, I'd try the paperclip method first, if the cel does not blink then trace the wiring.

 

[BrooklynBay]

What kind of scanner do you have? Did you check the modulator to see if it's broken? You might be losing ATF in the engine through the vacuum line.

 

[92exp4x4]

Modulator is definitely bad, not sure if that will keep it out of overdrive though. It will burn a few courts of trans fluid if i drive it consistently. TC lockup doesn't work either which tells me there is an electrical problem, probably a ground. My scan tool is a higher end craftsman tool for OBD 1 and 2 applications. Not the best but better than most. I haven't had a chance to hook it to another vehicle yet to verify it. I was using it on newer stuff recently. I might try this tonight on one of the explorers.

I was really hoping to verify my CEL. I'm expecting trans circuit fault or lean/rich codes from burning trans fluid.

 

[BrooklynBay]

You won't see a check engine light for a transmission code on a 1993 vehicle. That will only show up on a 1996 or later vehicle. From what I've read on this site, the 1995 Explorer (not Aerostar) has a 4R55E, and will show transmission codes. The 1995 Aerostar was the last year of the A4LD, so it won't show transmission codes.

 

[92exp4x4]

Interesting, I thought there is a circuit open code on the 3-4 shift or TC lockup. I figured the PCM could at least sense an open? I never had to check into it before so I'm not sure.

Now I'm really curious!