lqchrispl

I have been chasing the fix to these codes (P0100 & P0101) for about 7 months now. I bought the car and the previous owner told me the ecu has been recapped and i went into the LS400 group in facebook and the guy who did it confirmed it for me so that is ruled out i think. I have tried 2 oem and 2 aftermarket air flow meters. I changed the connector that plugs into the maf. And also did some diagnosing from a repair manual that i had someone send me and everything looked like it checked out. My efi fuses r not blown and are getting 12 volts. So at this point im assuming i have some sort of short or open in the wiring harness but i really dont know how to go about this issue anymore.

Some symptoms my car has is, most of the time the engine doesn’t stay on on the first crank but always on the second, very strong gas smell but haven’t noticed any black smoke, my speedometer and tachometer stop working intermittently and i know that goes back to the ecu so i’d like some feedback on that, sometimes at 40 and/or 60 mph it will stop accelerating but if i let off the gas and press it down again it will continue accelerating like normal. And sometimes the engine wont turn over at all, but if i let it sit for a bit and go back to it, it will start fine. And i only get about 150-160 miles to a full gas tank

Any help will be greatly appreciated since i love this car but all these issues make it hard to be driven daily.

Thanks in advance

Arsenii

Hello,

What happens when the MAF sensor is Disconnected?

You may need to get something like a Portable Oscilloscope, here is a link, and connect it to the Output of the MAF Sensor, then get an OBD2 scan tool and check the MAF Sensor Readout. Compare the numbers you see on the Oscilloscope to the numbers from the Live Data - normally you should be getting about 3.5 - 4g/s, maybe just a little more, which I think should be close to 1 - 1.5V on the Output of the Sensor. If you have access to some kind of a compressor, you can try running the same experiment on the bench, with only necessary wires connected and blowing into it with the compressor, that will verify that at least the sensor is functional.

As a sanity check, attached the pinout for the MAF Sensor below, here's hoping it's correct. With that, depending on what you see in the Live Data, and depending on what happens when you unplug the MAF sensor, it may be that you are not out of the woods with the ECU just yet.



Hope this helps and best of luck!

lqchrispl

Hope im replying to this correctly im new to this forum 😂. When I disconnect the maf nothing changes it tays running no type of bogging or change in idle, stays the same. I have not checked the g/s yet my old scanner didnt have that but i just picked up a new one and i’ll get back to u on that. What do you mean with the compressor? Sorry i dont get it, if you could explain it in a little more detail my apologies.
And i have tested voltages with maf at the maf and have checked continuity at the maf and ecu and everything seemed to check out to me. Thanks for the response

Arsenii

Since I can see it, you did at least something right..

Is P0101 Code still present with the Sensor disconnected? That would spell some bad news..

P0101 indicates that MAF sensor readouts are way beyond expected range for the current conditions, like if you are getting 2V or more at idle, which should be physically impossible, this code should not be tripped if there is a circuit malfunction, like a disconnected sensor.

I was referring to an air compressor for power tools in the garage, or just about any constant source of air, even a Leaf Blower would work now that I think about it. The idea is, instead of using the Engine to drag air through the Sensor, you blow air into it to see if you will get the Output from the sensor, verifying at least partially that the sensor is working and is not causing the faults mentioned. With that, seeing that you replaced it 3 or more times by now, it can be omitted.

So what was the Voltage you got on the Output, or Pin 2 of the MAF sensor while the engine was running?

Hope this helps and best of luck!

lqchrispl

Is P0101 Code still present with the Sensor disconnected? That would spell some bad news..

I fixed a vacuum leak a couple days ago and cleared the code drove it around and it didnt come back so thats good news.


So what was the Voltage you got on the Output, or Pin 2 of the MAF sensor while the engine was running?

Pin 2 is VG if I’m not mistaken, i got 1.3volts and was able to get it up to 2.7 when revving. (I have the readings for all the pins i’ll go ahead and attach those pics)


These are from a couple months ago. 1 and 3 read at about a volt lower today, and 2 was at 1.3 as i said. Idk if them being lower means anything but thought id let u know


I took my air intake off last night and didnt realize i didnt put it back on 😂 it started up just fine with no maf sensor plugged in and was reading 0.37 g/s with no sensor and when i put the sensor back on it read 0.36 g/s.

Hope this helps and best of luck![/QUOTE]

Anything helps man, i appreciate u taking ur time to help me.

lqchrispl

Is P0101 Code still present with the Sensor disconnected? That would spell some bad news..

I fixed a vacuum leak the other day and erased P0101 and went on a drive and it hasnt come back, so thats good.


So what was the Voltage you got on the Output, or Pin 2 of the MAF sensor while the engine was running?

From pin 2 i got 1.35 volts and was able to get it up to 2.77 volts when revving the engine.


I took my air intake off last night and forgot to put it back on and it started just fine without the sensor. It read 0.37 g/s without the sensor and then read 0.36 g/s when i connected the sensor again


And i have readings of all my pins i’ll go ahead and put that on here also.


These readings are from a couple months ago and theyre all down about 1 volt. Pin 2 dropped .4 volts as i saw today, and pin 4 and 5 were still at 0 volts.


Hope this helps and best of luck![/QUOTE]

Anything helps, i appreciate you for taking the time to help me out

Arsenii

At least that's good..

That sounds normal, don't see any issues with the Sensor itself, at least nothing blatantly obvious.

Are you sure? It's quite a difference, especially if there wasn't anything to cause it..

Gotta wonder if the issue is with the wire that goes from the MAF sensor to the ECU, below is an ECU pinout, try measuring the Voltage on Pin 8 of the ECU to see if the signal from Pin 2 of the MAF sensor does make it back there. If not, you can make a temporary jumper wire from MAF directly to the ECU and see if at least the code would go out, maybe even get the readout from the sensor.



Pin 1 is Constant 12V, Pin 4 is Ground, Pin 5 is a separate Signal Ground.
Pin 2 is MAF Sensor Output, Pin 3 is Temperature Sensor Output.

I don't trust wire color a whole lot, never had much luck with it, likely because I rarely have a complete manual for a specific car, either way, Pin Number is more trustworthy for me. Since you don't have P0110 for Temperature Sensor, I would assume that it works and the ECU recognizes it, so it's safe to ignore at the moment, leaving Pin 2 as the one that causes your issue, and the one to focus on.

Hope this helps and best of luck!

lqchrispl

helping a ton thanks brother
still kinda confused with this replying stuff but i bolded my responses 😂😂

Arsenii

What was the RPM when you got that value? At Idle (700 - 900 RPM) you should only be getting somewhere from 1.2V to 1.4V.

Did you check the Voltage across Pins 2 and 8 of the ECU? The idea is to put One lead of a multimeter on Pin 8 of the ECU, and the other to Chassis Ground, essentially any bare metal spot on the frame. Pin 2 that I was referring to is on the MAF Sensor, its output. It would be helpful if you can post a picture of what it looks like on your end, may save a lot of going back and forth.

Here is a thread on how to de-pin a connector, go to any local junkyard and cut a wire harness from under the hood, pretty much any connector there will have the pins as on your MAF sensor. De-pin one of the Terminals out of your newly acquired connector, then de-pin a Pin 2 Terminal on your MAF sensor, and replace it with a Terminal from the Junkyard, making sure to isolate the original terminal with electrical tape so that it doesn't short out.

Next, crimp any wire long enough to reach from MAF to the ECU onto the terminal that you just pinned into the MAF sensor, then solder a sewing needle on the other end of said wire, which you can then jam into Pin 8 of the ECU, making sure not to damage anything.

An important precaution - make sure that your MAF Connector housing is still sturdy and flexible, if the clip broke off of it, chances are the latches that hold the Pins will snap as well, in that case you will either have to source a new Housing before proceeding, or avoid this procedure in the first place. Practice before tearing into the real thing, get a bunch of connectors from the Junkyard and try taking the pins out of them, if you damage your only good connector, or worse, bend one of the terminals in said connector, it may be a good while until you can get that car back on the road. And also, make sure to disconnect the battery..

When you are quoting a reply, said reply is displayed in the text box with Quotation Marks on each end, refer to the picture below, so long as any part of the previous response that you are quoting is within those Marks, it will be displayed as a separate quote.



Hope this helps and best of luck!

lqchrispl

Okay yes i get it i think

lqchrispl

Okay yes you were correct on cold start it was at 1.4volts and dropped to 1.3 once it warmed up


i was checking voltage from pin 2 on maf to pin 8 on ecu, so i was doing it incorrectly, but from pin 8 on ecu to chassis ground i got .61 volts



And when it comes to depinning the connector i do understand that part ive depinned my maf before to tighten up the terminals i just didnt understand the jumper wire part but i do understand now, i went to the junkyard and got some wire and terminals so im ready to do that now, but since i did get .61 volts i’ll wait for ur response to see where i should go from here

thanks brother

Arsenii

That's more like it.

Yeeeah, you were basically checking the voltage on both ends of one wire..

Was the car running at the moment when you got that voltage?
Did you get the readout from the MAF sensor and the ECU at around the same time and in the same conditions?
Also, it's hard to tell from the picture, did you put a needle under the seal of Pin 2 on the MAF sensor or de-pin it?

Usually if the wire is damaged, you won't get anything on it, or the signal will be quite unstable, to get some erroneous voltage on it is quite strange. If the Pin 2 of the MAF sensor was disconnected when you checked the voltage, and said voltage dropped when you plugged it back in, it can signal an internal short inside of the ECU, causing the voltage drop, hence the questions written above. If you have more than one multimeter, try hooking up to the Pin 2 of the MAF sensor and to the Pin 8 of the ECU at the same time to see if you are getting the same exact signal on both ends, I would be genuinely surprised if you won't.

Sometimes what could also happen is you didn't get the right pin, just to state the obvious, the Pinout linked earlier is showing the Terminal Side of the connector, not the Wire side, looking at the connector from the Back mirrors the Pin Numbers. Connector Housing should have Pin Numbers stamped on it near each Row if you were to get lost in the numbering.

Either way, I've been there before, so it pays off to verify that you did get the right pin.

Hope this helps and best of luck!

lqchrispl

Yes the car was running when i got both readings, and i got both readings within 3 minutes of each other so yes same conditions. And yes i back probed and put a needle under the seal and connected my alligator clip to the needle. I dont have another multimeter but i dont mind picking up a cheap one tomorrow, i need to figure out whats wrong with this car its been like 7 months trying to figure it out, i feel like the car is just lying to me at this point idk if thats a possibility 😂

And yes when im counting the pins i unplug it and go left to right, so when i plug it back in itd be right to left if im not mistaken, i’ll double check that tomorrow tho