chron_bon
New Member
- Joined
- January 20, 2019
- Messages
- 8
- Reaction score
- 8
- City, State
- Vancouver
- Year, Model & Trim Level
- 1993, XL 4 Dr 4x4 315k km
Hi everyone.
Finally I'm able to contribute back to this forum after coming to it for so much information. I've seen a few threads of this forum and others about people with these KOEO codes and the behaviour I'm about to describe. I couldn't however find anybody who posted a follow up to what was the issue. This is that follow up from my own experience for anyone who needs some help with this.
1993 Ford Explorer XL 4x4. My phone camera is broken so I don't have any photos.
First, I was only able to get the KOEO error codes since the vehicle wouldn't idle. It would fire up for about a second then die. If I gave it some gas it would run incredibly rich and incredibly roughly, vigorously shaking around. This happened to be the first time I fired it up after a clutch replacement but these two things as I found out have nothing to do with each other. So a whole slew of seemingly unrelated sensors failing simultaneously and an internal voltage error on the PCM. How was this resolved?
Step 1: Think critically. I started by first looking on google. As I said, this didn't get me very far. So next I looked at the engine wiring diagram and noticed all the 1XX codes/sensors shared a common wire, and the purge canister/fuel pump are both get 12V from the same point. I suspected that I had either melted a harness while getting my exhaust bolts off or nicked a couple wires when I wrestled the transmission out. I started by checking the voltage on that common wire (grey/red) and found that it had no voltage but did have continuity between all 3 sensors showing errors. It was not shorted to ground, just floating. Then I checked the fuel pump relay and it was getting the proper voltage and the relay was working. Purge canister solenoid was getting 12V.
Step 2: Re-evaluate now that I'm presented with more information. I took a night to think it over and figured that my best bet would be to check that grey/red wire all the way from the PCM to a sensor as my issue either lies in the connector to the PCM or in the PCM itself. The internal voltage error sounds like either a component failed inside the PCM or a 12V wire for a power supply has come loose/broken. My grey/red wire had continuity between the sensors and the connector to the PCM. I also looked on google at photos of the PCM and noted that it had electrolytic caps in it and those are certainly past their mean time before failure at 27 years old.
Step 3: Debug the PCM. If you're still getting the same symptoms as me then we probably have the same issue. I opened the PCM to check the caps. Sure enough 2 out of 3 had failed and the acid had poured out of the bottom. If you're not comfortable with soldering/PCB repair I think this is the perfect time to learn because your PCM is likely dead unless this is fixed. Also, this board is from the early 90's, it's only 2 layer with wide traces. If you don't want to I would suggest buying a new (used) PCM and putting it in to see if it resolves your issues as it did mine.
Step 4: Replace the caps in the PCM. All of them. If you don't know where to go to get them I would suggest Digikey or Mouser. These sites are intimidating if you don't know exactly what you need. You will go to Products-> Discretes -> Aluminum Electrolytic Capacitors then start narrowing it down with the parametric search. You need 105C rated or higher, the same voltage rating as you currently have (different PCM's may have different caps but it will say on the side) or higher, and the exact same capacitance you have. +-20% is fine and common. Try to stay under 100V so they aren't too large and the leads don't break off in the future due to the extra weight. don't worry about the other parameters. The capacitors will have a line down one of the sides, make sure you put the new ones in with the same orientation.
It is incredibly important that after removing the failed capacitors you thoroughly clean off any acid and corrosion. If you don't your board will fail again in the not so distant future. Use q-tips, tweezers and IPA to scrape/clean off any and all corrosion. Thoroughly inspect the area near each capacitor for broken traces. The acid ate through one of mine and I almost missed it. To fix this carefully scrape away the layer over the copper (solder mask) on either end of the trace about 2-5mm and jump it with a thin piece of wire or solder blob.
Step 5: Put it back together and cross your fingers. hopefully this resolves your issue and the repair is a success.
Finally I'm able to contribute back to this forum after coming to it for so much information. I've seen a few threads of this forum and others about people with these KOEO codes and the behaviour I'm about to describe. I couldn't however find anybody who posted a follow up to what was the issue. This is that follow up from my own experience for anyone who needs some help with this.
1993 Ford Explorer XL 4x4. My phone camera is broken so I don't have any photos.
First, I was only able to get the KOEO error codes since the vehicle wouldn't idle. It would fire up for about a second then die. If I gave it some gas it would run incredibly rich and incredibly roughly, vigorously shaking around. This happened to be the first time I fired it up after a clutch replacement but these two things as I found out have nothing to do with each other. So a whole slew of seemingly unrelated sensors failing simultaneously and an internal voltage error on the PCM. How was this resolved?
Step 1: Think critically. I started by first looking on google. As I said, this didn't get me very far. So next I looked at the engine wiring diagram and noticed all the 1XX codes/sensors shared a common wire, and the purge canister/fuel pump are both get 12V from the same point. I suspected that I had either melted a harness while getting my exhaust bolts off or nicked a couple wires when I wrestled the transmission out. I started by checking the voltage on that common wire (grey/red) and found that it had no voltage but did have continuity between all 3 sensors showing errors. It was not shorted to ground, just floating. Then I checked the fuel pump relay and it was getting the proper voltage and the relay was working. Purge canister solenoid was getting 12V.
Step 2: Re-evaluate now that I'm presented with more information. I took a night to think it over and figured that my best bet would be to check that grey/red wire all the way from the PCM to a sensor as my issue either lies in the connector to the PCM or in the PCM itself. The internal voltage error sounds like either a component failed inside the PCM or a 12V wire for a power supply has come loose/broken. My grey/red wire had continuity between the sensors and the connector to the PCM. I also looked on google at photos of the PCM and noted that it had electrolytic caps in it and those are certainly past their mean time before failure at 27 years old.
Step 3: Debug the PCM. If you're still getting the same symptoms as me then we probably have the same issue. I opened the PCM to check the caps. Sure enough 2 out of 3 had failed and the acid had poured out of the bottom. If you're not comfortable with soldering/PCB repair I think this is the perfect time to learn because your PCM is likely dead unless this is fixed. Also, this board is from the early 90's, it's only 2 layer with wide traces. If you don't want to I would suggest buying a new (used) PCM and putting it in to see if it resolves your issues as it did mine.
Step 4: Replace the caps in the PCM. All of them. If you don't know where to go to get them I would suggest Digikey or Mouser. These sites are intimidating if you don't know exactly what you need. You will go to Products-> Discretes -> Aluminum Electrolytic Capacitors then start narrowing it down with the parametric search. You need 105C rated or higher, the same voltage rating as you currently have (different PCM's may have different caps but it will say on the side) or higher, and the exact same capacitance you have. +-20% is fine and common. Try to stay under 100V so they aren't too large and the leads don't break off in the future due to the extra weight. don't worry about the other parameters. The capacitors will have a line down one of the sides, make sure you put the new ones in with the same orientation.
It is incredibly important that after removing the failed capacitors you thoroughly clean off any acid and corrosion. If you don't your board will fail again in the not so distant future. Use q-tips, tweezers and IPA to scrape/clean off any and all corrosion. Thoroughly inspect the area near each capacitor for broken traces. The acid ate through one of mine and I almost missed it. To fix this carefully scrape away the layer over the copper (solder mask) on either end of the trace about 2-5mm and jump it with a thin piece of wire or solder blob.
Step 5: Put it back together and cross your fingers. hopefully this resolves your issue and the repair is a success.
