[YukonJay]

Roger. Thanks. Is there anywhere you would start first? Short of replacing every wire on that 5v ref circuit.

 

[Bex]

Maybe best to start at the yellow connector to the ECU - Y23 - which when looking at the back of the connector, is on the bottom row, second from the left, which is where the grey/red connects to. There should be 5v there with key on.

 

[YukonJay]

Bex thanks. Was thinking of this. Bench test ecu. Make sure I got 5. Pull all wires out of the harness involved in that circuit. Add them back one by one starting with that one and watch to see if I drop the ref again. Think that will work with just key on? Or am I missing wires that would be powered up running?

 

[Bex]

I don’t have the FSM for the 16v but the grey/red circuit is not terribly complex. I’d backprobe the connector for the grey/red at the ECU while the wires are hooked up to their circuits, and see if you get the 5v reference there, with the key on. If so, and it is steady, then you know that your difficulty is with the wiring between the ECU and the sensor.

 

[YukonJay]

Bex,

I don’t get 5v at back of ecu on the ref wire with the tps unhooked or hookedSo I assume it’s one of the other wires getting cross feed with 12v and shorting it out like gv said

 

[2013GV]

Bex,

I don’t get 5v at back of ecu on the ref wire with the tps unhooked or hookedSo I assume it’s one of the other wires getting cross feed with 12v and shorting it out like gv said

find the ref wire at the ecm and remove it from the plug, then probe the pin the wire was connected to to confirm ecm is outputting 5V with key on, then work out from there. If there's a short on the ref line anywhere, the voltage will drop to 0V at the ecm.

I don't condone this course....but....you could find a suitable point in the loom and cut the wire and do it that way, but its a bad methodology to use, cutting a wire to separate the circuit.

 

[YukonJay]

Gv

Yeah have same voltage at pin Wire pulled back of ecu. And it’s low. Not zero. 1.5-2.5 ish. Drops and car runs like shizer. So...12 volts crossed on some other wire in the ref circuit cause that?

 

[2013GV]

Can you confirm the following please
You should have 5V out if the ecu and nothing on the reference line itself As its disconnected? If you don't have 5V on the reference output from the ecu, that's the first concern. That could be a dried out capacitor or a fault in the 5vdc regulator circuit internal to the ecu

 

[YukonJay]

Gv,

Gotcha. I haven’t tested the line disconnected I’ll check that. Still got to make sure the ecu is ok. Yeah if I disconnect the ref lines from the ecu and then test them for voltage that would show which ones getting cross fed. But do you know if I would be missing a powered line or two without having the car running? Testing key on?

Thanks

 

[YukonJay]

Also....

One more. I backprobed every pin on the ecu and checked it against the fsm and they all read good. If I was getting 12v somewhere I shouldn’t because of a chaffed wire shouldn’t I have seen something out of whack somewhere? Too high a voltage on one of the ref lines??

 

[2013GV]

if you have disconnected the reference lines and the ECU is putting out the correct voltages, then the only choice is start tracing till you find the issue thatts dragging the voltage down

testing the wire with key on and only that wire disconnected from the ecm should show any issues on that circuit, I would expect there to be no voltage on the wire on the "downstream" side away from the ecm.

 

[YukonJay]

Roger. Thanks GV. I’ll do that. Never thought to test the wires unplugged from the ecu to see if they were picking up voltage. Hopefully I can find something that way

 

[Bex]

Also....

One more. I backprobed every pin on the ecu and checked it against the fsm and they all read good. If I was getting 12v somewhere I shouldn’t because of a chaffed wire shouldn’t I have seen something out of whack somewhere? Too high a voltage on one of the ref lines??

So you are saying that you DO have the 5v reference coming directly out of the ECU. So, your issue is somewhere in the harness wiring, presumably.

 

[YukonJay]

Yeah Bex

I get 5 out of the ecu and then it seems to slowly fall off. Sometimes over the course of weeks. Also seems to take awhile to come back. Like days. With the batt unhooked. Do have a new batt. Here’s what I was going to try n a few weeks as don’t have time to mess with it right now.

• bench test ecu with the harness pins... Will prove good relay and ground if ref holds steady. - plug harness and watch ref. If bad then pull all ref circuit pins and check for cross voltage on them. If all 0 volts replace one at a time watching ref. Find which one drops ref hopefully and rerun. If nothing shows up watch alt voltage for spikes. If that’s good rerun ecu to batt ground and power also. If that don’t do it maybe rerun all the wires in that ref circuit
• 
  Letme know what y’all think and I’ll tell you what I Find. Thanks
• 
  
  

 

[Bex]

Still not quite sure I understand. You advise that you DO get 5v when backprobing the connector AT the ECU (so that wiring is out of the picture), and that it slowly falls off, AT the ECU?? Or is it slowly falling off, as you‘re testing the wiring itself. You need to identify whether its a fault IN the ECU, or with the wiring. And frankly, if you have the ECU out, open it up and look to see if you have the big Rubycon capacitors with the X on top. The 16v should have 2 of them. If they are still in your ECU, replace them. There’s info on the forum about where you can get the replacements, etc.

By the way, please put your car’s specs into your signature, so we don’t have to hunt through this thread to remember what you’re driving....

 

[YukonJay]

Bex

91 sidekick 4dr 4x4 16v 1.6l manual transmission (mpi) don't know how to add that...🤷‍♂️🥶

THIS ecu is good. Just had it rebuilt. Least it was good. Hopefully hasn’t fried it. It’s def in the wiring somewhere. Just haven’t been able to find it yet. But now I know it’s def in the wiring. 2013gv guys suggestion that I got a 12v line rubbed through to a ref line somewhere makes the most sense at this point. Does my rundown on how to find it make sense? And any other ideas what keeps making the frign thing drop off??

 

[Bex]

Go into your control panel, and add your car’s specs there, in your signature. It will then show in the bottom of all of the posts you do.
If the problem was with the 12v going to the ECU, or the. ECU ground, then I would think that you would see your issue in more circuits, instead of just one. Again, you say that, when testing the pin AT the ECU, that you get 5v....but then it drops off? It drops off AT the ECU? Perhaps it’s far easier to run an entirely new wire from the TPS to the ECU, in place of the grey/red...????

 

[YukonJay]

Bex

It’s not the grey red. With harness plugged in and grey red wire removed reads exactly the same as at the tps. I get 5v with only the power and ground hooked to ecu. Then for awhile after I plug in the whole harness then it drops off. Makes sense would have other circuits screwed up with bad power ground. Think I’ve got a 12v wire somewhere in the harness rubbed through to one of the wires on the ref circuit???