Ok, it appears there’s definitely a problem in the wiring harness or computer. Not THAT surprising, after all that’s the diagnostic code is saying too.
If I had that problem I’d repeat the test w/the battery disconnected as the next step. After that I’d repeat the test with the ECM disconnected from that section of the harness.
Just did that. I disconnected the ECM and the battery. The DVM showed “Open Circuit”. Then I connected the ECM and left the battery disconnected and between Terminal 6 and the others, now says 15 M ohms. Also, when the red probe is in terminal 6, it won’t read resistance. I have to swap the probes like I did earlier.
Do you mean it reads zero ohms?
No. It shows “OL” which means “Open Loop”. But I just read on a site that it maybe means “infinite” too. Hmmm…
Anyway… I made a quick video so you can see the test and the results: Testing Oxygen Sensor Harness - YouTube
So with the battery disconnected, key “off”, one way it reads 15 Mega-Ohm and the other (swapping probes) it reads OL (meaning infinity)? But when the battery is connected it reads 15 Mega-Ohm one way, and zero ohms the other?
BTW, I think OL means “overload” rather than “open loop”. It just means the meter can’t display that high of ohms. It’s normal for an open circuit.
hmmm … let me take a look at the circuit diagram …
No sorry… when I said “zero” I was referring to “OL”. I was mistaken. Sorry. So, with the battery connected it would show the same conduct as you saw in the video.
Here’s the diagram, let me know if you need a better close up.
Double check that when the battery is connected you get the “zero” ohm reading like before.
Ok, so you either read 15 Mega-ohm, or OL when measuring from 6 to 1 , 2 … 5 with ECM connected, sensor disconnected, harness side, battery connected or not. If that’s correct, I don’t see any obvious problem with the connection from the sensor to the ECM.
The P2231 codes suggest a short from pin 1 to either pin 5 or pin 6. But your test doesn’t show that in the harness anyway. Pin 5 doesn’t go to the ECM, it goes to the main relay. You might try removing the sensor 1 fuse at the main relay, see if that makes any difference. I doubt it will, though.
Otherwise either the sensor remains problematic, the ECM is faulty, or the wires from the sensor to the ECM aren’t quite reaching the ECM. Maybe an open circuit somewhere, possibly at the ECM connector.
Have you measured the voltage at pins 1,2, 3, & 4 with ignition on, engine off? Similar to when you measured pins 5 & 6?
I double checked the resistance with the battery connected and ECM connected too. Yes… it’s “OL” (open loop) between 6 and 1,2,3,4,5.
Also, voltages are:
Terminal 1 = 2.2v
2 = 2.5 v
3 = 2.5 v
4 = 2.2 c
5 = 12.2 v
6 = 4.4 v
That all looks correct to me. I don’t see any obvious problem. My guess is either there’s an open circuit in one or more of the wires from the sensor to the ECM (less likely, but possible), or there’s a problem w/the ECM itself. If you’re up for it, suggest you start by measuring the resistance in the harness (each wire, one by one) from the sensor side to the ECM side (ECM disconnected).
Note there could still be a problem on the sensor side. I presume you’ve already tested for shorts between pin 6 to 1, 2, …4 on the sensor itself, and from 5-6 you measure the heater resistance, around 3 ohms probably.
One more note, remember that there could be an intermittent short in the harness remaining. It might not show up until the engine twists from rotational inertia forces, which moves a wire.
Another idea, look for problems like bent pins on the ecm connector, both sides. Your diagram above shows which pins to focus on.
Ok, I will test the harness starting from the connector all the way to the ECM. Also, I tested the sensor itself. Resistance between terminal 5 and 6 is 3.0 Ohms.
Good suggestion. Not sure where else to start… This one is interesting for sure!
Got me to thinking about what was the record number of posts and what was the issue. Seems to me we hit something like 900 with no resolution.
I did not see “replaced idle control solenoid”, only cleaned, but I could be wrong. Now here is the danger, after exhausting all possibilities, we start over thinking some of the items replaced might be defective.
Did you test the isolated sensor for shorts between the heater and the other pins?
Yes. Also, I went to Auto Zone and got a new oxygen sensor cause it was under warranty. I erased all codes. I installed the sensor and it still the same. Shaking as hell, very rough and codes P0301 and P2231 came back again.
That’s a tough one. You pretty much have to solve the P2231 before you’ll be able to address anything else. The o2 sensor function has to be working correctly for the engine to run well.
hmmmm …
I think you know this already, but the straightforward solution is to take your car to a Hyundai dealership shop for the diagnosis. You can fix it yourself, but you need to know what’s wrong. They’ll have the advantage of advanced scan tools so they can monitor the o2 sensor’s signal levels as read by the car’s computer in real time. And they can do a fuel trim test.
(Oh oh, There’s a photo right above this post in a “Pics that went too far” advertisement of a cute girl in a semi-transparent tube top, zooming in and out of the top, that’s distracting me, so consider this post as possibly bogus … we men are hopeless … lol … )
Ok, back to your problem. First step, make sure the P2231 code is really cleared. If it then comes back, if I had this situation and wanted to continue the diy’er approach, I think I’d figure out a way to monitor the output of the O2 sensor as I drove. e.g. run a wire to the driver’s compartment, connected to a DVM. If nothing unusual shows up, the problem must be on the ECM circuit board, or the ECM connector.
Another idea, disconnect the sensor’s heater circuit wiring temporarily, as a diagnostic procedure. If there’s a short there’s nothing for it to short to. Note that it could be illegal to drive the car with that modification, EPA rules etc.
Removing the ECM and looking at it closely under good light and magnifying glass might show a problem, broken trace, solder bridge, etc. Always risky to remove the ECM tho.
OK, one more stab. What does this tell you? In open loop the computer is using pre determined settings to run the engine. When the engine warms up it goes into closed loop using the readings from the various sensors.
So if you don’t have a problem in open loop but do in closed loop, use your computer to compare what is substantially different in closed loop. Still I’d put in a brand new OEM TPS. Especially when you find there is nothing significantly different between open and closed loop.
The oxygen sensor fault will cause open loop, so will the misfire.
I would start with a compression test on cylinder # 1.
Next exchange fuel injectors with cylinder # 1 and another to see if the misfire changes cylinders.
The oxygen sensor problem needs to be solved but not if cylinder has no compression.
The rich mixture caused by the failing fuel injector or misfire may be causing a high O2 voltage fooling the computer to believe the sensor input is shorted to voltage.
When I took out the injectors rail, I swap the injectors. #1 to #4. After that I keep getting the misfire in cylinder 1.
I just did a compression test. Here’s the results:
cylinder 1: 155 PSI
cylinder 2: 160 PSI
cylinder 3: 170 PSI
cylinder 4: 170 PSI
