chasing intermittent signal to ecu (code 11)

[7M4EVR]

This is driving me nuts...

When I drive the car 99% of the time it runs great, no problems whatsoever, no codes. Occasionally though and what seems to be at complete random the mil will come on intermittently and soon after the car will lose power and stall. (This is scary at 60 mph when the car starts to coast and the steering gets stiff.) Every time this has happened and left me stalled I wiggle all the connectors to the ecu and usually she starts back up and runs fine for days again but the code 11 as expected will now be there. I don't know if I hit bumps and move something just enough to cut power (this seems plausible) but it has happened on the highway with no bumps and not on gravel with rumble strips..

Anyhow...on the tsrm it shows the different circuits and relays where the problem will be but I'm hoping for some advice on where to start and how to correctly test these, and possibly save some time and test the likely source of the problems first. I'm learning, but still extremely slow at reading wiring diagrams so please bare with me. Another concern is everything is intermittent so won't something only fail a test when I am experiencing this problem or there is no power to the ecu? I took off the grounds under the intake Mani cleaned them and put them back on, no change. I know this is useless info but the wires that seem to help when I wiggle are the hac wires that lead down to the connector mounted on the glovebox frame and the like 4 pin wire coming directly out of the back of the ecu (the only male connector coming off the ecu, what is this?)

 

[supraguy@aol]

I believe the connector hanging off the ecu only has turbo indicator, defog, and headlight relay wires.

 

[7M4EVR]

I believe the connector hanging off the ecu only has turbo indicator, defog, and headlight relay wires.

Yep thats the one..

And I'm sorry for being an idiot but i think i RE-found the issue. This damn IGN fuse keeps coming back and haunting me!!!! I dont know why i keep forgetting about this stupid fuse...Im about ready to burn both of my driver side kick panel fuse boxes and get a new one. Both of them are missing one of the metal prongs in the ign fuse slot causing the 7.5 ign fuse to get intermittent ground. I had to bend one of the prongs of the fuse to sit tight in the fuse box slot and to get good ground.

I don't think it has anything to do with wiggling wires i think it has more to do with me getting out and opening and closing the door causing the fuse to move a bit, or just dumb luck. This may not be the case but I'm willing to bet. I will be pulling the fuse box out and trying to somehow add a metal connector to the IGN slot so the fuse can get proper ground. Anyone have any experience doing anything like this?

 

[Nick M]

I'm hoping for some advice on where to start

I wiggle all the connectors to the ecu and usually she starts back up and runs fine

This is a clue.

 

[7M4EVR]

This is a clue.

Don't think i found my problem aye? I was really hoping it was that easy. But it is weird that wiggling the wires seemed to help, your probably right. Willing to tell me if I'm on the right diagnosis path? Here is the only info i can find on code 11:
Ignition switch circuit, Ignition switch, Main relay circuit, Main relay or the ECU. So by probing IG SW, +B1, +B, and Batt, with the positive on my DVOM and the neg to Ground, that will pretty much tell me where the issue is right? I should see 12V to all of these? Also, will i have to do this only during the time I'm experiencing the symptoms to catch it? Take it easy on me lol

 

[super51fan]

Are any of the connector clips broken? IE: Slide the connector and it locks into position.
The connectors going to ecu.

 

[jetjock]

Loss of voltage (it's not a ground) on IGSW will certainly cause that symptom.

 

[7M4EVR]

Are any of the connector clips broken? IE: Slide the connector and it locks into position.
The connectors going to ecu.

not at all man, woulda noticed the obvious issue there. They all clip and by visual inspection none of the wires coming into the ecu connectors "look" bad/damaged/loose. But we all know what the visual tests tell us, NOTHING!

 

[7M4EVR]

Regardless of ign fuse voltage (thanks), or the voltage loss somewhere on the ign sw circuit that's where im gonna start when i get home tonight. Hoping my problem is somewhere between the battery and the ECU on the IGN SW circuit. Would be really nice if it was blatently obvious lol.

 

[Nick M]

Constantly moving wires around or the PCM can subject the female end to stress it isn't meant to have. It is possible you are loose. There is even a "feeler gauge" for the pins to make sure they have not opened up. As I said, it is a clue that should be investigated further. Eyeballing it is not the answer.

 

[jetjock]

Nothing good technique with a quality meter can't solve...

 

[7M4EVR]

Here is a pic of my ECU pins i don't have said feeler gauge, but none of these feel loose to the touch at all.


This is somehow where my issue is and i don't see how. It's not my IGN fuse and it's not my ign wires coming into the ecu. In fact I individually wiggled every wire coming into the ecu and none made any difference until i touch this dangling plug. How can this be if this is just the turbo indicator, and headlight plug? Is the only possibility that moving that plug is shorting something else?


It does appear to be missing a metal prong or two.

On a side note I have driven the car for 50 more miles after putting it all back together, and it hasn't happend again. However, i would like to know the cause instead of just hoping it doesnt come back.

The weirdest thing i am experiencing right now, and maybe this has something to do with it, is my VF at idle and cruise will not stay above 0.02, it will bounce from 0.05 and back down though. I know the VF signal is working because it acts normal on decel. Doesnt matter if i adjust fuel pressure at all and the AFM screw is all the way backed out. I'm thinking my AFM is on it's way out because i had a code 31, and wouldnt run right one day, and now it's gone and runs great??

 

[BryanDyer]

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=96

 

[IndigoMKII]

Sounds like your harness is chewed to hell and back.

 

[Nick M]

View attachment 70861
Here is a pic of my ECU pins i don't have said feeler gauge, but none of these feel loose to the touch at all.

That is the male side, not the female side.

How can this be if this is just the turbo indicator, and headlight plug? Is the only possibility that moving that plug is shorting something else?

It can't. Not unless the harness has been cut and spliced elsewhere.

The weirdest thing i am experiencing right now, and maybe this has something to do with it, is my VF at idle and cruise will not stay above 0.02, it will bounce from 0.05 and back down though.

0 from VF can be more than just lean if you do not do the pins right. It can mean a code stored.

I know the VF signal is working because it acts normal on decel.

And what does it do on decel? Since during decel you go lean, with injection being halted.

I'm thinking my AFM is on it's way out because i had a code 31, and wouldnt run right one day, and now it's gone and runs great??

More likely a wiring issue than the photo sensor or the LED quit working, then started working again.

 

[7M4EVR]

Thank you Nick....

-I did notice the female ends of the ign wires coming into the ECU connector are a tiny bit loose, but when i played with them it didnt change anything at idle leading me to believe that wasn't the cause of my issue (not saying it shouldnt be fixed though).

-I don't think the harness was cut and spliced anywhere, there is no evidence to support that and the car did not have this issue before rebuild. I'm guessing somewhere along the harness there is an exposed wire and moving this plug disturbs it. Going to be fun to find...

-I completely forgot about that! I wiggled that plug causing the code 11 again and didnt clear codes before testing VF! And what i meant by acting normal on decel is the fact that it actually fluctuates up a little, but never over 1V. (I was just indicating that I knew I had the VF and E1 terminals jumped properly).

-I traced my harness from the afm as far as i could until it went under the intake mani, and then from the ECU into the firewall and couldnt find one apparent questionable spot. My harness is honestly not that bad at all. I have a feeling that completely ripping my harness out and going over it is going to be my winter project!

Will continue my troubleshooting...thanks for the info!

 

[7M4EVR]

Welp I had a suspicion this little problem was going to show itself again...this time I have no choice but to figure it out indefinetely because i have no power to the ecu at all now. Car stalled on me and no matter what wires or fuses I wiggle I cant get power back to the ecu. Upon inspection of harness i noticed it was melted to the egr valve pipe under the intake mani. I pulled it off, cut the tape around the area and inspected the wires. Only one wire was melted its yellow (still havent traced what it is yet). Im thinking it melted this wire enough to ground it out against the egr pipe and possibly ruined my ecu. Visually went over the harness inch by inch and this was the only noticeable problem. I fixed the melted wire and troubleshooted:

All lights work except the MIL
All fusible links are good in the fuse box. Not sure where fusible link 2.0L is?
I have power at the efi fuse, and ign and gauge fuses in kick panel
12 V from batt to E1
12 V from batt to body ground
0 V from M-REL to E1 and/or body ground (ign sw on)
0V from +B(+B1) to E1 and/ or body ground (ign sw on)
4.8 V from IG SW to E1/ and or body ground the first time I checked, and .05 V the second time I checked (Not sure what i did different here may have accidently had the ign off the second time, need to re test this but I know it wasnt getting close to 10-14 V either way)
Bought a new EFI main relay and no difference

Since I have power from batt to E1 Im assuming wiring from the ecu terminal to the ground is good. And since all the fusible links (aside from the 2.0L that i cant seem to find) and i have power to my fuses am I right to assume that I may have fried my ecu? Is there any way to test the ecu itself to see if its good? Im open to testing anything else that may narrow down where the issue may lye.

 

[supraguy@aol]

Sorry to hear about your luck.
I was going to tell you that the only time my car ever shut off on me, was when a wire rubbed against the egr pipe, and kept blowing the efi fuse, and was going to suggest you check that area. But then I saw your last post and laughed. Not AT you, just the irony. Not sure if you might have blown the ecu, but I'm sure it's possible when you get wires shorting together.

 

[ATL88Supra]

dead ecu bro

 

[7M4EVR]

Yeah I have a new one on the way to try. Not 100% that he ecu is dead but testing per the tsrm seems to point to it, guess its easy enough to try a new one. Hope that melted wire was the issue so I dont fry the new one. Kinda weird how easy it is to ruin an ecu you would think that there were failsafes built in. I thought thats what the fusible links were for, but Im sure the wire that grounded out was the one wire that will ruin the ecu if grounded...newtons law and my luck.