Am I reading this resistance result correctly?

Your measuring this with all the plugs removed from ECM like in your picture ?

 

Voltage, no.

 

What are you checking for Kristi?

 

Anything off (not right). I have had a high, hunting idle for over a year. I have done all kinds of buttoning up (gaskets, hoses, etc). Checked various sensors. Replaced some. The latest was the TPS. It was definitely in need of replacement. Did that. All the settings line up meaning closed is 9.8, etc. Whelp, idle went up. Crap like that keeps happening.
I don't throw codes very often. Usually only when I say, unplug something whilst the truck is running.
I'll pass a smog check & then not. I did before I did the TPS & now I'm not.
All that is the baseline for my frustration.
& has brought me to here. One more thing though. My EFI fuse blew sometime last summer. I replaced it & the idle went down. Why did it blow though? Anyway, thought I'd see how to check the ECU, & logical or not, am now focusing on those things that share the B+ power & ECU ground wire & this is how I ended up here.

 

Thanks for this. One of the things I had done was clean up the engine bay grounds. Missed the one under the data link, though. Maybe it’ll help? We’ll see….

 

If it can reach, probe a seat anchor bolt. Pretty sure those are clean and very well connected to the body.

Oh, and make sure you stab it.

 

Great advice.

I will add, cheap meters don’t help either.
I’ve had cheap meters show different readings just moving the wire to leads.

I’m not saying you need a Fluke, but a good Klein or Craftsman Automotive meter is worth the investment.

 

So I have b+ at the ECU backprobed. No key. When I put it to body ground, engine bay or door, I get .76v. Coincidence that it’s the same amount of ground I am getting at the pos signal hot wire on the O2 sensor?

 

Still not sure if I’m supposed to get any ground at the pos signal wire. The neg signal wire is not hot.

 

Why measure the voltage with everything off? If you're checking ground, I'd think you'd want to check resistance which should be near 0, or continuity to show that ECU ground is connected to body/frame ground.

 

I'm pretty sure B+ floats when key is out.. Almost 1V is a quite a bit but not worrisome yet. Without checking your wiring diagram, the O2 positive is probably floating as well. You should have very high resistance between a floating point and ground (ideally infinite), so if that's the high R you've been measuring, then it's fine.

With truck running, these should be near-battery voltage when negative probe is grounded.

 

Should I have continuity from the B+ at the ECU to the B+ at the O2 sensor? I have ground to ground continuity.

 

Yes, Both of those are powered by the same supply.
The 20A EFI fuse feeds power to them through the EFI Relay.

 

The manual is intending that you check the resistance at the ground for the component, not a random place on the chassis. Bad grounds are a notorious cause of electrical issues of all kinds, and it's very common for corrosion, especially when you have multiple connection points, to cause high resistance and subsequent problems. Disconnect the body ground for the ECEM, clean all the connectors and the body point, reconnect and try again. If you see anything green and puss-like (aka, "the green crusties") chances are good you've found if not all the issue, a big part of it.

 

There are .72v at terminal 3 (think I have that correct, the non-hot terminal - 30 or 87) of this relay (key off), which very, very slowly starts to decline when the relay is pulled. Also, anywhere from 3.-ish M ohms - 10.-ish M ohms. Fluctuates sometimes quickly, sometimes slowly. Seemingly no rhyme or reason. Pulling the main power outlet fuse has no effect on this terminal 3 voltage. It does cut off the hot terminal voltage, as it should.
Seems to maybe be affected by my pulling the EFI relay, which is right next to it. Slows down the fluctuation. They are on different circuits as far as I can tell.
Would I be correct in thinking that since there is no capacitor involved in this circuit that this should not be happening? (Should not be any reserve voltage. Not even sure if a relay can function that way).

 

I am getting continuity across pins 3 & 5 (load side) of the EFI relay at the box. No key.
This should only happen with key at start or acc, correct?

 

Yep, seems like it should not be connecting with power off.

does it click when you switch the key back and forth?

 

Someone above mentioned the use of a good quality meter, and I agree. For something as hard to track down as your issue seems to be, you can make it a lot less painful on yourself if you are using good equipment (and using it properly).

Im always super cautious using the 'auto range' feature on any meter for any reason. Its very easy to mistake a reading of 0.9M ohms (0.9 million ohm or 900,000 ohms) for a reading of 0.9 ohms. The first being extremely high resistance (essentially an open circuit) and the later being very good conductivity.

If I want to prove I have or test for continuity between two points Ill use the lowest Resistance setting on my meter (for example 200 ohms). In that setting I know whatever the meter displays is the value, in ohms. No k's or M's to worry about. If the value is higher than 200 ohms the meter will show something like Lo, -1, or nothing depending on what model / manufacturer. For the purpose of grounds, anything over a few ohms is probably a no-go anyway. If Im testing a certain component then I would set the meter to the next higher range. For example 2000 ohms setting for a 1.5k resistor, or the 20k setting for a 10k resistor.

Hope that helps a bit.

 

Are you testing the relay?
Or testing the terminals in the fuse box?

 

i’ll try that when I get home in a bit.

At the box. No key.