1991 3FE w/ 190k miles, stock. Driving down the freeway and the engine dies. Tans Temp, Brake & Voltage light come on. Get off the road and turn the key off and then on, no CEL. Drag it home and replace the alternator, which is what I have when the 3 lights have come on before. Replace the EFI relay, which usually bring the CEL light back on. After all that, still no CEL and the Trans Temp, Brake & Voltage lights are still on. Go through the CEL checklist and get to the B+ connector and no +12V. I go through and look at the connectors and fuse and everything looks okay. Any ideas? By the way I have never had to post before because I can usually find the answers in older posts. This site is very helpful. Thanks for your assistance.
3FE - No CEL and no +12V @ B+
- Thread starter sillygirl
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
Couple of things:
1. You got the dash lights because your motor stalled, not because your alternator was failing. Without the engine running and the key in the ON position, you're always going to get those dash lights.
2. You won't see +12 on the check connector if the EFI relay is open. You can't check fuses and connectors by looking at them with eyeballs. You need to check voltages with a meter.
Please follow my EFI flowchart.
http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf
1. You got the dash lights because your motor stalled, not because your alternator was failing. Without the engine running and the key in the ON position, you're always going to get those dash lights.
2. You won't see +12 on the check connector if the EFI relay is open. You can't check fuses and connectors by looking at them with eyeballs. You need to check voltages with a meter.
Please follow my EFI flowchart.
http://www.sdsysdesign.com/tlc/images/Strife/3FE EFI Diag.pdf
3FE Fusible Link
I've had this happen a couple of times on the 3FE trucks-- both times has been the high-current fusible link up by the battery.
I've had this happen a couple of times on the 3FE trucks-- both times has been the high-current fusible link up by the battery.
- Thread starter
- #5
Well I figured that at freeway speed the transmission would turn the engine enough to spin the alternator, so I may have been hasty replacing the alternator.
Yes, I followed John's checklist and every thing was good till I got to the..."Check for +12 on pin 8 (B+) on the CHECK CONNECTOR mounted on
the right side of the fire wall. If +12 on pin 8 and still no CEL, then EFI
circuit OK and problem is with ECU or related wiring." I also jumped the between pins 2 & 4 which still does not light the CEL, which reaffirms an ECU issue.
So I'm moving on the the ECU and related wiring, but is there a common malfunction/weak link? Many of the issues associated with the 3FE seem to be common and I'm just wondering if there is something I should check first? Thanks.
Yes, I followed John's checklist and every thing was good till I got to the..."Check for +12 on pin 8 (B+) on the CHECK CONNECTOR mounted on
the right side of the fire wall. If +12 on pin 8 and still no CEL, then EFI
circuit OK and problem is with ECU or related wiring." I also jumped the between pins 2 & 4 which still does not light the CEL, which reaffirms an ECU issue.
So I'm moving on the the ECU and related wiring, but is there a common malfunction/weak link? Many of the issues associated with the 3FE seem to be common and I'm just wondering if there is something I should check first? Thanks.
- Thread starter
- #7
Okay so started investigating the ECU. As I got to the ECU there was a faint burnt smell behind the glove box and recalling a similar burnt smell when the engine died on the freeway, I opened it up. Attached is a photo of the fried resistor on the ECU. Yes, I realize that I need a new ECU but will the next one do the same thing when I plug it in? Was this the cause or the symptom Any thoughts?
An auto transmission won't force the motor to turn over because there is not a direct connection between the two. A manual trans will do so because the motor and transmission are directly coupled. The torque converter (a fluid pump) sits between the motor and the rest of the automatic transmission is efficient at pumping fluid in one direction to provide power to the trans but the converse it not true.
As to the real question at hand...I got nothin'.
Wow. That is a rarety to say the least. I don't have a schematic of the ECU internals so I've got nothin for you. I would say to make sure ALL fuses are of the CORRECT VALUE before putting in a known good unit.
- Thread starter
- #10
Yes I have checked all the fuses (with a meter) and eyeball to confirm the correct values were installed. I have not changed or blown a fuse in the 8 years I have owned the vehicle. The other bit of information that I have is that right after it died and I did not have a CEL I swapped out the EFI relay (have one in the glove box) and noticed that the one I took out was scorched on the pin 1 & 3 side. Knowing that the EFI relay gets hot I didn't think too much of it. But could a voltage spike have caused both of these items to get toasted? Just grasping at straws...
I was hoping someone had a schematic for the ECU because I would like to try and replace the bad resistor, but I can't read the colors. Yes, I realize that there may be other things fried on the ECU, but at least I could see if the replacement resistor was instantly toasted. Right now I don't think I could make the ECU worse.
psfpilot-So when you let off on the gas on say a steep downhill isn't an autotrans "forcing against" the engine? Don't you get compression braking in a gas powered vehicle. If you had a kill switch and could turn off the engine on the downhill and the instant the engine stopped firing you would be in uncontrolled freewheel because the trans can't force the motor? I just pondering the concept not questioning your advice or wisdom which are appreciated.
I was hoping someone had a schematic for the ECU because I would like to try and replace the bad resistor, but I can't read the colors. Yes, I realize that there may be other things fried on the ECU, but at least I could see if the replacement resistor was instantly toasted. Right now I don't think I could make the ECU worse.
psfpilot-So when you let off on the gas on say a steep downhill isn't an autotrans "forcing against" the engine? Don't you get compression braking in a gas powered vehicle. If you had a kill switch and could turn off the engine on the downhill and the instant the engine stopped firing you would be in uncontrolled freewheel because the trans can't force the motor? I just pondering the concept not questioning your advice or wisdom which are appreciated.
Any resolution to this? I just had this happen to me in a 1997 FZJ80. I have no CEL, I can jumper pins 2 and 4 of the EFI relay and get a CEL with the key on. I read the ECM and no codes. However it still won't start.
Edit, ended up being fusable link for me.
Edit, ended up being fusable link for me.
Last edited:
Hi there kinda awkward to reply after so many years but I am facing the same issue with my fj80, 3fe-1991. Today I opened the ecu n same found this...please help
wow -- that's the exact same resistor. sub'd to keep an eye on this. Good luck.
-Derek
-Derek
