Code 31

[Badmanners]

Hey guys,

I just purchased a 92 ls400 that was sitting for quite a while. Maybe a year and a half. I am going through the whole car and catching up on delinquent maintenance. I recently replaced the fuel filter and cleaned the MAS. After I put everything back together and started it up I took it on a short drive and noticed that is was struggling at Idle when I stopped, Cut out as I accelerated. When I got the car back to the garage I cut it off and cut it back on and got a CEL. when I counted the code off the flashing CEL I got code 31. I assumed I had not plugged in the MAS correctly or did not clean correctly and re did those steps. I’m still having the same issue even after I reset the system.

other Known issues are that the dash lights flicker and temp gauge reads normal then pugs to max and then normal, and the Odometer and speedometer do not work. I am hoping these issues are related to the pulling on the wire harness in the back left of the trunk hinge.

but I can’t figure out why is was running fine and now can’t idle to save its life. Any suggestions would be much appreciated. Thank you for your time.

mph and yes I confirmed the fuel is pointing in the correct direction.

thanks again.

 

[gloverman]

If code 31 reoccurs after clearing then I flick another afm into it and recheck

Dash units frequently fail too.

 

[Badmanners]

That’s what I was thinking as well. I have already located a couple of candidates on eBay. I will also test the MAF when I get home.

yes faulty dash seems to be an ongoing problem with the early ls

 

[77highlux]

If it's a 92 and it's a Fuji MAF throw it away. When you use MAF cleaner on them they shit the bed, they have a special coating that becomes deteriorated when you do so and it throws the circuitry into a loop.

Order a new MAF and install it, you can check to see if it's in spec by running a basic diagnostic to pins 1 and 2. should be between 2-3V at room temp. You can also test the circuit to ensure it's got the right juice. 5V at pin 4 when the car is ON but not running and ground to pin 5 with vehicle OFF.

 

[Badmanners]

Thanks highlux,

yes it is the original Fuji. That makes me feel better knowing those things are junk if cleaned. I found a replacement and it’s ordered. Just waiting the the part to get here. I also ran the the test with my meter, and the current is very erratic jumping all over the place. This was extremely helpful thank you.