P0171 toyota corolla 1.8 hybrid

[Guest]

Hi everyone hope for abit of help. Got a 1.8 corolla hybrid 2019 and today the eml came on and all of a sudden the car is drinking fuel haha. Got a code reading and all it says it p0171 too lean. Where is my best starting point here to check and I do have some data on my scanner what should I be looking for. Also not sure if it is same but there is a really really bad egg smell from exhaust too. Thanks any info would be great.

[flash22]

look at your freeze frame data for when that code comes up

look a your short and long-term fuel trims as well as your 02 sensors

[Guest]

Iill check for you thanks. I'm not too technically minded what is the difference of short and long term fuel trims and what am I checking for in them 

[Bper]

Hi Ant,think of fuel trim as adjusting the air fuel mix. Both short term and long term trims are percentages.

Short term adjusts right away for things like acceleration. It should be close to 0% most of the time. Big swings indicate potential issues.

Long term learns over time and makes bigger adjustments. It should also be near 0%, but a little tolerance is okay (around +/- 10%). Big deviations here are more concerning.Hope this helps.

[Guest]

Really appreciate the comment, ill check in morning on data and get back to you. Thanks 

[Guest]

Also just to pick your brain do you think the lean condition could cause the smell of is that more likely a cat issue ?

[taxidriver50005]

How's the 12v Battery... That's normally the bad egg smell as Battery is getting cooked... Under the impression they have gone back to lead acid Battery as its in the engine bay. 

[Guest]

Battery was test few weeks ago and was told it was perfect, the smell definitely seem to be from exhaust as I turned it off and I got right up close to end of exhaust the smell was very very strong 

[Guest]

Did do it when running for split second but didn't really want to be breathing in exhaust fumes haha

[Roy231]

The exhaust smell is because it's over fueling hence the lean code, the ecu will add fuel to compensate, the fuel trim will be higher than normal.

Check hoses around inlet manifold for splits and the one from the air cleaner a vacuum leak can cause a lean condition amongst others i.e sensors.

[Red_Corolla]

Check that the coolant temperature is normal and not reading cold all the time (should reach 80-90C when it's warmed up). Air leaks is a good suggestion. Also, there is a mass air flow sensor in the inlet duct and this is normally easily accessible. You might try running the car with this unplugged - it will lose performance and set another code, but it's a simple way of eliminating the sensor from the potential faults (assuming the overfuelling issue doesn't go away).

[TonyHSD]

All good suggestions here. If I can ask where the car is parked at night and how much and how often do you drive? 
Very likely and very common a rat infestation and some wires on these sensors might be chewed. We had this case already here. It was spark plugs wires. Check thoroughly engine bay. 👍

[Red_Corolla]

5 hours ago, TonyHSD said:

All good suggestions here. If I can ask where the car is parked at night and how much and how often do you drive? 
Very likely and very common a rat infestation and some wires on these sensors might be chewed. We had this case already here. It was spark plugs wires. Check thoroughly engine bay. 👍

Damaged wiring can indeed cause a vast array of implausible problems. If Toyota are still using the same misfire detection that they have for many years then it's difficult to see why coil wiring would cause a misfire to go undetected by the ECU. The computer monitors a single wire for pulses which get generated as the coils discharge - same wire connects to all four. Any gaps in the firing pattern should generate a code and also shut down the associated fuel injector. At least, that's the system they employed in the past.

Another cause of misfire which can be harder to detect electrically is carbon tracking around the outside of the plug (i.e. firing outside of the cylinder). It's worth pulling off the coils and having a look inside the rubber boots for any tell-tale traces.

[taxidriver50005]

May or may not be related but a friends prius gen 3 stunk of bad eggs and it turned out to be faulty EGR valve causing it.... Not exactly sure how but dealer replaced valve and smell disappeared 🤔🤔

[Red_Corolla]

1 hour ago, taxidriver50005 said:

May or may not be related but a friends prius gen 3 stunk of bad eggs and it turned out to be faulty EGR valve causing it.... Not exactly sure how but dealer replaced valve and smell disappeared 🤔🤔

Yes EGR faults can cause fuelling issues. Their job is to allow a certain amount of exhaust gas back into the intake, so it will have an effect on the mix ratio if not working correctly.

[Saxmaniac]

You need to look at data and let that follow what you investigate, no good making random guesses. If you're not sure how to proceed, there's loads of videos on YouTube, Scanner Danner, Pine Hollow Diagnostic, Automotive Test Solutions all walk you through a proper method to trace problems. You'll find video case studies tracing lean codes or whatever, so worth learning off those people. I think Toyota will have wideband upstream O2 sensor so that works in a different way to the normal type. Total fuel trims are the important thing, add long and short term trims to see the true state of things 

[TonyHSD]

Egr issues are simple. If the valve gets clogged or stuck closed the engine will starve for air and will have wrong air-fuel ratio mixed with all related issues.