chinoawl

Hi All,

My partner was driving on the highway with no issues, when all of a sudden the car died and wouldnt start or sputter back up.

Towed to shop, they diag'd as Fuel Pump. Just replaced, and now they are saying "when the pump was replaced they tried turning the car back on and it went into limp mode and decided to check and realized that the pcm was going out. they reset it and now it is intermittent" (whatever intermittent means here, this is 2nd hand so these are all the details I have)

Their suggestions are to trade it in or go to the dealership.

Anyone have any experience with this or any ideas? I've done fuel pumps before, and never had electrical issues afterwards. Bad diag from the start?

Felix

Yeah, that's what I'd say also. Never heard of both going bad at the same time before. Possibly replaced the pump as it wasn't getting power, to confim, I would of bypassed the electical system & used a jumper wire direct to the pump. Seems like that shop is just parts changers, & can't diag, so tells you to hit up a dealership. Wow.........

Leeper

The usual "Hey, we're gonna throw your money at problems we know little about and if it doens't work we'll still charge you high labor rates". The dealer will do the very same jsut at a far higher labor hourly rate. They'll learn things on your dollar and time. I hope you did not actually have to pay any labor on the first attempt since they did nothing to actually solve your issue yet cost you precious time

Margate330

No way he diagnosed a bad ecm unless the mechanic has a whole lot more data that was not told to the customer.

Because he can't figure it out, trade it in or sell it? Lol

​​​​​​What are the codes? 🤓

I'd drive around with a scanner plugged in and monitor the fuel trims too

PS, as OP suspected and asked, I agree it was a bad diagnosis from the start or the job got botched. Lol

>> Welcome to Club Lexus and your 1st Post!

spinellib

That would infuriate me.
And, yeah, if indeed the pcm was smoked, I would suspect they smoked the computer, too, with their "diagnosis."

Margate330

I do advanced diagnostics for my job and I will say that intermittent electrical faults are the most difficult of them all.

Since they went ahead and put in a new fuel pump AND if we can assume the job was done properly, this means the easy stuff was already done and now the hard stuff begins -aka- chasing down intermittent demons. lol

PS- I'm not a fan of firing the parts cannon but in my work, it's invaluable to have good known working pieces to swap in to find faults so in this special case, I'd buy a fuel pump relay just for this diagnosis and keep it for a spare if it doesn't fix the problem.

Here's where I'm at so far and I made some notes on it.
(Posted in fair use for commentary and discussion).

spinellib

Phil, that's a great diagram; it's like a flow chart.

Maybe best to just start from scratch and treat this as a Crank/No Start. Confirm fuel, confirm spark, etc.

Margate330

Thank you @spinellib !

Yeah, your right, we actually don't know for a fact that it's fuel related. Lol 🤣

My notes above are for fuel related going off mechanics fuel delivery diagnosis however more info is needed.

Probably best to start over.

chinoawl

Well I wrote a whole reply but it got deleted.

In short,
picked up car today. No issues 45 mins home. they said it entered limp mode when they replaced fuel pump, resetting pcm (i think they mightve had to do it twice) resolved it. their concern is that the pcm is dying. I assume though its just bad data from when the car died from fuel pump issue?

Car seems good now. Any ideas?

Leeper

Ideas - yes, run codes also use Techstream for real-time data

spinellib

Or perhaps they found and corrected their error and don't want to tell you what really happened. Who knows, maybe they broke/unplugged a connector in their "diagnosis" without knowing it.

chinoawl

Update::


Driving today, 40 min trip (~90 mins of driving since picking it up), no issues. On the way back, it's stalling when slowing down to stop, or when we stop moving. Car seems fine under power, we will see if it resolves itself again.

Any ideas?

chinoawl

I will be able to run codes on it tomorrow night, I'm out of the area right now

chinoawl

Battery, check engine, and oil light are on

Leeper

no help without knowing what the codes are... are you certain your battery is fully charged? Not that it might be "new" but fully charged... that is the first thing to look at. Do you have a maintainer and/or charger? Once you've established the battery is 100% post the codes