Hi, a few days ago i tried to start my car. Foot on the brake and then i press start button, the engine crank then dies after that i start again and the engine run normally. Until now there is no more problem. I check for error code then found P1604 Startability malfunction which has many causes

But this has happened before not often, maybe 2-3 times in the last year. At first i thought maybe i don't press the brake hard enough but on the 2nd and 3rd i'm pretty sure i press it hard enough. my car is at 80k km nearing 90k km. in my last service i changed the fuel filter (not assy just the one that looks like paper) and the mechanic told me to change spark plug in the next service.

What could possibly be the problem ? is because of worn spark plug ? or fuel related ? i always use 98 Ron fuel. and i changed my battery in early 2019

Thank you

 

Symptoms are as follows:
https://www.autocodes.com/p1604_lexus.html

I'd start with getting the battery load tested. Most auto parts stores can do this. Also make sure to look at the negative terminal cable to the body for corrosion. Do you hear any unusual noises coming from the fuel pump?

 

I last check my battery in September, and i always check battery every 3 month for warranty purposes and it always show good result. the negative terminal looks good and don't show any corrosion

I read that this error code should be ignored if nothing happen afterward. is it really a code that should be ignored ? I'm afraid that this is going to get worse and might not start on the 2nd or 3rd attempt in the future

Thank you

 

Update

I changed my spark plugs and I figured out what cause that, if on the previous day i turn the ignition on then off a few times without turning on the engine (i often adjust audio setting and listen to audio without turning on the engine) then the next morning it will failed to start on first attempt and on the second try it will start and i could smell a bit of gas.



All 6 plugs looks similar to this



Fuel Trim

From what i read spark plugs that look like that and negative fuel trim was caused by rich engine, and i did trigger too rich cel earlier this year (i fixed this by cleaning the maf sensor). Also my oil smells like gas (Running less than 5k Km an 6 month). Is this caused by leaking injector ? if yes can it be fixed without changing the whole injector ?

Fyi. gas in my country is not really good, others who use the same car often get cel too rich after filling up at a certain gas station

Thank You

 

So you already changed spark plugs? If so reset ecu. I'm assuming you take very short trips in the car? After reseting ecu go for multiple long trip drives. You will notice the LTFT get closer to 0. Then as soon as you start to do short trips again they will get higher at times. Hopefully staying under 5% -.

Another thing is you only need to hit the push start once to listen to the radio? If you're doing it twice your in the on position.
Cold weather these cars run very rich until fully optimal range. Then short trips don't help much either.

Anytime you change critical sensors MAF especially. You'll want to reset LTFT BACK TO 0.
ECU reset will do this for you fuse method is the simplest.
https://www.clublexus.com/how-tos/a/...our-ecu-363500

 

Double Post

 

I think i had reset the ecu after changing the spark plugs, but I did reset the ecu again today and do a long trip after that. The ltft for bank 1 decrease to -13 while the bank 2 stays the same at -10, hopefully the ltft will go down further after more long trip

How long should I wait after turning on the car ? Should I wait till the rpm drop to normal ? Or should I just go right away ?

Yes this car is mostly used for short trip, since this pandemic the car is used for around 10km a day, around 20km before the pandemic.

The radio turns on on acc, but often I pressed twice so the beeping noise go away when the door is opened..

Thank you for you reply

 

This is what you should see on a fresh LTFT wipe. I just did it now since I was putting in new DRL bulbs in my headlights. It's a pain since I have aftermarket headlights, and requires bumper removal. Also I normally reset ECU at least once a month, because during the rainy periods on my way to work. I'm running behind semi trucks for long periods at a time. I'm using the lower F-sport airbox which has a rather large opening. Water tends to pool up in that area. So driving in the rain is not good with this mod. It will eventually soak the air filter.

If you don't see the LTFT at 0 try again this time leaving the fuses out for longer. Another is disconnect the negative side on the battery. Though for this to work it's best to leave it for anything past 15 minutes. So once you start your car, and find your radio stations are still as they were programmed it did not work.




Fresh ECU reset.

Usually I let the car sit for 15 minutes till the RPMs settle. If you don't have the time. Yes you can drive it till the RPMs stabilize. Just be prepared to have your foot on the brakes
as it will want to go forward.

 

Ohh i check the LTFT after the trip, i didn't check it right after starting, but i think it reset because i left it for 30 minutes and the radio preset is gone. I will try this again and look at the LTFT right after starting and wait until the rpm stabilize.

Thank you for your reply.

 

Once the RPMs stabilize the LTFT's should be under -10%. This should be normal. What you want to pay attention is to STFT's. They should be relatively low under 5% +/-. Once the shorts goes past 20% +/-. That will trigger the check engine light to come on giving you lean, or rich.

So if you're cruising around, and STFTs are relatively close to 0 that is good.

You can read here:
https://www.autoserviceprofessional....fuel-trim-data

https://m.youtube.com/watch?v=pIJdCZ...ture=emb_title

 

The STFT's were always under -5, it was the LTFT's that often go over -10.
Anyway thak you very much for your help, i think i will reset the ecu more often just like you and hopefully it won't be a bigger problem in the future.

Thank you