94 Explorer CEL. Please help interpret codes

[stcroix949]

94 Explorer Sport with 125000 mile has been showing 2 codes for a while and I can't figure out how to fix it.
This is an OBD1 system.
The codes are:
212- Loss of Ignition Diagnostic Module signal to the PCM or SPOUT circuit grounded.
226-Ignition Diagnostic Module signal not recieved.
The truck runs fine, gas mileage good.
I took the Ignition Control Module to NAPA to be tested and it checked out OK. Also seperated and cleaned some of the connectors and looked for possible wiring problems.
Also, my Chiltons manual says the PCM is located on the drivers side firewall above the wheel well but for the life of me I can't find it. The servo for the cruise control is there.
Is there anybody out there that can tell me what to do to fix these codes? Thanks in advance.
Brad

 

[verlane24]

I had code 212 for a while too with no driveability problems either.... but it went away after changing the spark plug wires and resetting the computer. I doubt that is what fixed it, so I'm thinking I may have a loose connector somewhere.

Code has not come back after ~100 miles, so we'll see. I am interested to see what everyone has to say....

later
brian

 

[Rhett]

PCM location on 94

Originally posted by stcroix949
Also, my Chiltons manual says the PCM is located on the drivers side firewall above the wheel well but for the life of me I can't find it. The servo for the cruise control is there.

The PCM on our trucks is located in the passenger side kickpanel, accessible from the cab. Sit in the passenger front seat. The PCM is behind the side panel by your right foot. A couple of phillips screws and one plastic pushpin hold the panel in place. Beneath is the pcm.

 

[stcroix949]

Thanks for the reply. Found the PCM where you said. Kind of troubles me that the Chiltons manual was so far off in identifing the location. Seems like kind of an important bit of information.
Now if I could get some info about the trouble codes. Someone else must have had to fix them!!!!
Please dive in even if it's a guess.
Brad

 

[Runnin'OnEmpty]

Brad, the code 212 and 226 are related, as you probably figured. When you fix one code the other will disappear. The IDM signal is sent to the PCM indicating the coil has fired. It's "loss" will not affect anything except the tach. It either will not work, or work erratically. The engine will run fine without the signal.

Even though the ICM checks out fine, it could still not be sending the IDM signal. The testers that the auto parts stores use may not be sophisticated (yeah I can spell!) enough to check all of the ICM functions.

You could also have a shorted IDM circuit wire somewhere. If you can find the wire, you could check it with a multimeter and wiring diagram. It'll run from a pin on the ECM.
Don

 

[stcroix949]

The tach has always worked as it should.
Am going to look for a short in the ECM wiring harness. I remember I had a darn mouse make a nest out of the fiberglass insulation for the AC last fall. Maybe he did some damage to the wires that are routed beneath the power box.
Brad

 

[Runnin'OnEmpty]

Now that's a strange one. As I understand it, the tach runs off the IDM signal.....? Anyway, that's a good idea to look for mouse damage. I vaguely remember that a section of the IDM wire runs under the battery box, and that this is a good area to look for shorts/opens in the wiring loom.

I had the same trouble with a Tree Rat (squirrel) last winter. I have a Bronco that sits outside due to lack of garage space. Every time I parked it, the tree rat would climb in the engine compartment and eat his dinner on the warm manifold. When I opened the hood, the engine compartment had nut hulls all over it....