MplsBinks

Hey GX Fam, I'm stumped and need some help. My 2011 GX 460 (100K on the clock) is acting weird.

The other day I started it and it immediately shut off upon firing up. No sputter. Just a clean shut-off like I pressed the button again.
I then tried to start it again, it fired up, and I drove home. It ran great as usual.

The next morning I started it and it immediately shut off upon firing up like the day before.
I then tried to start it again and it just cranked. A CEL light came on.
I plugged in my CEL reader and it says there are No Codes in the system (odd).

Later in the day, I fiddled around with the Fuel Pump Relay and it didn't make a difference.
I then went inside and messed with the ECU Fuses. I replaced one of them and it started. Just to test it, I put what I thought was the bad fuse back in and it started again. Odd. Drove around the block, ran great.

This morning I started it and it immediately shut off upon firing up. Tried to start again, no dice. Fiddled with the same fuses, no dice.

CEL is on again, No Codes (tried a different reader in case that was the issue, still nothing)...It cranks hard. The battery is less than a year old. Connections are clean and tight. Runs great when it starts.

Ideas?

MplsBinks

I unplugged the Mass Airflow Sensor and it started right up. But it's in some sort of limp mode? The dashboard/speedometer lights aren't on, but 4 LO is flashing.
Seems like my next step is to clean or replace the sensor.

Doesn't really make sense why a dirty sensor would make the car just shut off immediately instead of running like poop and then stalling...but what do I know.

dwh13

Might be a long shot, but do you have any electrical accessories installed? I had these symptoms to a T, and we eventually traced it back to a faulty light bar I had installed directly to the battery. It was causing a positive to ground situation and randomly shorting out the entire electrical system.

MplsBinks

Good thought, but I don't. Completely stock.

bbqsoup

Just a thought, how about pull the battery cable and let it reset. It can't be a bad MAF as that would throw a bunch of lights too.

MplsBinks

Good call on the battery disconnect ^^^
That was my thought too about it not being the MAF since it didn't pull any codes (at least that my code reader could find), but the fact it started when I pulled it changed my mind.
I grabbed a new sensor and am replacing it tonight. If that doesn't work, I'll do the battery disconnect.

NewB2Lexus

I did not really get the "limp" mode post, you should be able to drive around with an unplugged MAF as the ECU will use some preset value in the absence of the values from the MAF. Does the GX drive normally with unplugged MAF?

MAFs normally don't go bad but at 100k it is certainly not a waste of money to replace one.

LFZWest

I've never had this type of problem on any of my Lexus vehicles.

But almost every type of electrical issue I have ever had. Was almost always fixed with a new Battery. When was the battery last changed?

klinquist

If you disconnect and reconnect the battery on the GX, it'll immediately shut off after first start. It's a GX thing.

So yeah - start there. Tighten battery cables?

NewB2Lexus

When I disconnected the battery to install the OE cooler it did not shut off after the first start. Maybe ours is a defective GX?

klinquist

Mine does this every single time, and no codes are thrown (checked with TechStream), so I assumed it was intentional.

dwh13

Same - anytime I disconnect the battery, it sputters before it starts.

Acrad

I've seen the initial stall after battery disconnect on my '12. IIRC.. it is related to a throttle body relearn... seemed to occur less on mine after I cleaned my throttle body.

Acrad

OP: Any progress? Any chance fuel pump is failing?

I don't think that triggers a code IIRC

emetb73

As I read almost all suggest check the battery or connections to it. I don't see any other reason what is can be.