Gotcha. I'm not familiar with that plug as I don't have one. I was assuming from the schematic that it was a junction of sorts but looks like a diagnostic port that doesn't connect anything together so probably nothing to do with that. I'll have to look more at the schematic when I get back.
1994 FJ80 won't start
- Thread starter ratchet
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- #22
Ok, no worries. I found this excerpt from the FSM that may be interesting. I know it deals with testing the fuel injection system but the diagram labels the terminals of the ECU which may help our search.
I just noticed that you are in Erie. I'm down south of Denver...when this is all over, regardless of whether we figure it out or I end up taking it in to someone to fix for me, we gotta meet up so I can buy you a beverage of your choice.
R.
I just noticed that you are in Erie. I'm down south of Denver...when this is all over, regardless of whether we figure it out or I end up taking it in to someone to fix for me, we gotta meet up so I can buy you a beverage of your choice.
R.
Ah I didn't realize you were up here, very cool. I can try and stop by if needed to go through some of this in person if it comes to it.
So now that I know that data connector is basically a diagnostic port on those trucks, can you check for voltage between pin 2 and 3 on the dlc (W and E1)? Looks like that would provide power (bypassing the ecu) to the check engine light so you might try a jumper to make sure you can at least get the light to come on that way. Is there any troubleshooting steps in your fsm for verifying the ecu using this dlc?
So now that I know that data connector is basically a diagnostic port on those trucks, can you check for voltage between pin 2 and 3 on the dlc (W and E1)? Looks like that would provide power (bypassing the ecu) to the check engine light so you might try a jumper to make sure you can at least get the light to come on that way. Is there any troubleshooting steps in your fsm for verifying the ecu using this dlc?
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This was in part of that pdf you sent me and we have verified some of these but might as well go back through and actually run them against the e1 pin. If you aren't able to find these pins let me know, these are all the ecu connection pins, but basically just test for voltage with one lead on the item to the left and the other the item on the right, which is typically E1 pin. Make sure you use E01 instead of E1 for ground when it tells you to. The ones with the blue mark are the ones I would test for.
I would assume if all the above check out fine, and you have good power and ground connections to the ecu, then it may be the ECU itself. I would verify that the pins to the ecu are clean and connecting to the connections well as a last check, and if you find anything in the fsm that allows you to jump that diagnostic port to verify the ecu operation that would be useful, though I can't imagine that would get you very far if we can't even get the MIL light to come on.
I would assume if all the above check out fine, and you have good power and ground connections to the ecu, then it may be the ECU itself. I would verify that the pins to the ecu are clean and connecting to the connections well as a last check, and if you find anything in the fsm that allows you to jump that diagnostic port to verify the ecu operation that would be useful, though I can't imagine that would get you very far if we can't even get the MIL light to come on.
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- Thread starter
- #26
Thats a hell of an offer thanks. I may take you up on that eventually since you may see something simple that I missed.
I verified that there is approximate battery voltage between Pin 2 and 3 on the DLC. I also put the jumper wire in and then the CEL came on (and never went out) when the key is turned to the on position. I guess that saves me from having to pull the dash apart to verify that the light works.
I also verified that there is approximate battery voltage at E7D13 fo the ECU.
As for the rest of the ECU checks mentioned in your last post, they are going to take me a bit. I'll post up the results when I get them but wanted to get this info out there in case it helps narrow something down.
R.
I verified that there is approximate battery voltage between Pin 2 and 3 on the DLC. I also put the jumper wire in and then the CEL came on (and never went out) when the key is turned to the on position. I guess that saves me from having to pull the dash apart to verify that the light works.
I also verified that there is approximate battery voltage at E7D13 fo the ECU.
As for the rest of the ECU checks mentioned in your last post, they are going to take me a bit. I'll post up the results when I get them but wanted to get this info out there in case it helps narrow something down.
R.
Ok very good. So yeah, the MIL just is not getting ground from the ecu. If you do all those last checks above, then I would do one last check on the connectors at the ecu, focus on the grounds and power pins, especially that E1 pin and make sure that you are confident the ecu is getting a great connection with the connectors. Wiggle that E1 wire at the connector where it connects to the ecu slightly and see, same with those power wires in the first 2 steps, I think if the ecu is good that it would have to be one of these pins not getting a good connection. Otherwise not sure what else could be the issue other than the ecu itself.
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- Thread starter
- #28
Well unfortunately I ran out of time yesterday and wasn't able to perform the ECU checks listed in Post 25. I'm going to be extremely busy over the next two weeks and, while I am going may have a few moments this Sunday, likely won't be able to do anything else with this until the weekend of the 21st.
I think over the next couple weeks I'll going to pick up another ECU so I can swap in a known good unit.
At any rate, I really appreciate all the help you've taken to help me with this. I'll be back at it as soon as I can.
R.
I think over the next couple weeks I'll going to pick up another ECU so I can swap in a known good unit.
At any rate, I really appreciate all the help you've taken to help me with this. I'll be back at it as soon as I can.
R.
- Thread starter
- #29
Well this weekend I finally got back to this. I have a friend who has a 1994 FZJ80 so yesterday I convinced him to let me plug my ECU in to his truck to see if it worked...which it did. This morning he contacted me and said that his idle was very low which was not the case prior to the ECU swap. I wasn't sure what was going on so I did some searching and found that when the ECU is reset (which was probably the case when I swapped them out) it needs a bit of time to relearn things and once that happens the idle would return to normal.
In the course of searching for the information on the low idle I found this discussion (Bad ECU?) in which the OP had symptoms very similar to mine and part of the problem ended up being the contacts in the VAF. Since that was a simple test I decided to try disconnecting the VAF connector prior performing the voltage checks mentioned in post 25. When I turned the key to on, while the VAF connector was disconnected, the CEL came on. This indicated there was a problem with the VAF or the wiring between it and the ECU. While I was searching for the idle information I ran across another discussion that indicated that if the two screws at the VAF (shown in the attached photo) were removed then bad things happen in the VAF. Once I read, that I remembered removing those two screws and pulling the connector from the body of the VAF before realizing that was not the correct way to disconnect it.
After inspecting the wires going to the VAF, I popped the cover off the VAF (it doesn't really look like its supposed to be serviceable but I figured that there was already something wrong with it and at worst I would be buying a new one anyway) and found that the little silver metal pieces (shown in the attached photo) were not in the right place and could potentially be touching each other creating a short. It is hard to see in the photo but it looks like the silver pieces are sandwiched between a piece of metal and the circuit board. As a result, if the screws are removed and the connector is moved at all the silver pieces move out of place. I used a small flat head screwdriver to put them in place and then got the two little screws (that I shouldn't have removed in the first place) put back in to hold it all where it needed to be. After that I set the cover on, connected the electrical connector and the vehicle fired right up. I haven't driven it yet but after I set the timing it was idling nicely so its looking good.
So the lessons I learned are:
-don't unscrew the connector at the VAF
-even if the ECU is getting power and has a good ground there still could be something else keeping it from working
-when the ECU is reset in a 93/94 FZJ80 it will take a while to relearn what it needs in order to idle correctly
-got to practice reading an electrical schematic and using a multi meter
-the community here at IH8MUD rocks (already knew this but it got reconfirmed)
Thanks to everyone who provided advice. Satchel, I'll PM you; I'd be grateful if you'd let me buy you a drink (or 10). I really appreciate all the time you took to walk me through this stuff.
R.
In the course of searching for the information on the low idle I found this discussion (Bad ECU?) in which the OP had symptoms very similar to mine and part of the problem ended up being the contacts in the VAF. Since that was a simple test I decided to try disconnecting the VAF connector prior performing the voltage checks mentioned in post 25. When I turned the key to on, while the VAF connector was disconnected, the CEL came on. This indicated there was a problem with the VAF or the wiring between it and the ECU. While I was searching for the idle information I ran across another discussion that indicated that if the two screws at the VAF (shown in the attached photo) were removed then bad things happen in the VAF. Once I read, that I remembered removing those two screws and pulling the connector from the body of the VAF before realizing that was not the correct way to disconnect it.
After inspecting the wires going to the VAF, I popped the cover off the VAF (it doesn't really look like its supposed to be serviceable but I figured that there was already something wrong with it and at worst I would be buying a new one anyway) and found that the little silver metal pieces (shown in the attached photo) were not in the right place and could potentially be touching each other creating a short. It is hard to see in the photo but it looks like the silver pieces are sandwiched between a piece of metal and the circuit board. As a result, if the screws are removed and the connector is moved at all the silver pieces move out of place. I used a small flat head screwdriver to put them in place and then got the two little screws (that I shouldn't have removed in the first place) put back in to hold it all where it needed to be. After that I set the cover on, connected the electrical connector and the vehicle fired right up. I haven't driven it yet but after I set the timing it was idling nicely so its looking good.
So the lessons I learned are:
-don't unscrew the connector at the VAF
-even if the ECU is getting power and has a good ground there still could be something else keeping it from working
-when the ECU is reset in a 93/94 FZJ80 it will take a while to relearn what it needs in order to idle correctly
-got to practice reading an electrical schematic and using a multi meter
-the community here at IH8MUD rocks (already knew this but it got reconfirmed)
Thanks to everyone who provided advice. Satchel, I'll PM you; I'd be grateful if you'd let me buy you a drink (or 10). I really appreciate all the time you took to walk me through this stuff.
R.
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