Check Engine with P2099 Code

[alxcrlsn]

Hello,

I just picked up my earlier this month, and about 200 miles in I had my first couple issues:

• ESC error with reduced acceleration (limited to 4k RPMs). I was able to fix this by restarting the car and it didn't come back.
• A few days later, a check engine light with a code of P2099 (Post Catalyst Fuel Trim System Too Rich - Bank 2). This persisted and did not clear after restart.

I made an appointment with my dealer, and brought the car in yesterday to replace the Bank 2 downstream O2 sensor. Upon completion the check engine light was off, and all appeared good until I was on my way home and the light reappeared. Once again, I also went into limp mode, but was able to resolve that by restarting the car. However, the P2099 error has returned and the check engine light is persistent. Worth noting that the light appeared and then some time went by before the car went into limp mode. They don't appear to be perfectly correlated.

I think it's safe to say that the O2 sensor isn't the issue, so I'm wondering now if it could be the ECU, wiring, or some other electrical gremlin. I live at a relatively high altitude, so I'm also wondering if that could be a factor. The limp mode is concerning but always seems to clear on restart. I did also notice that there is now sometimes a delay of a few seconds between pressing the start button and the car actually starting. However, when the car starts up it sounds good, and the car sounds and feels absolutely fine when driving.

I have a call out to the dealer today and I'm sure they'll work with me to resolve, but I thought I'd check here to see if anybody has experienced any of these issues, specifically the P2099. My dealer has been great to work with, but they're about 2 hours away so not looking forward to multiple trips back and forth to get this sorted.

 

[cyanmauve]

I hear you on the 2 hour trip thing. I am in the same boat. A CEL just popped up today, and I have been having intermittent failure to start issues. I want it addressed but to the dealership and back is a half day round trip for me.

 

[6spd_Emira]

Hello,

I just picked up my earlier this month, and about 200 miles in I had my first couple issues:

• ESC error with reduced acceleration (limited to 4k RPMs). I was able to fix this by restarting the car and it didn't come back.
• A few days later, a check engine light with a code of P2099 (Post Catalyst Fuel Trim System Too Rich - Bank 2). This persisted and did not clear after restart.

I made an appointment with my dealer, and brought the car in yesterday to replace the Bank 2 downstream O2 sensor. Upon completion the check engine light was off, and all appeared good until I was on my way home and the light reappeared. Once again, I also went into limp mode, but was able to resolve that by restarting the car. However, the P2099 error has returned and the check engine light is persistent. Worth noting that the light appeared and then some time went by before the car went into limp mode. They don't appear to be perfectly correlated.

I think it's safe to say that the O2 sensor isn't the issue, so I'm wondering now if it could be the ECU, wiring, or some other electrical gremlin. I live at a relatively high altitude, so I'm also wondering if that could be a factor. The limp mode is concerning but always seems to clear on restart. I did also notice that there is now sometimes a delay of a few seconds between pressing the start button and the car actually starting. However, when the car starts up it sounds good, and the car sounds and feels absolutely fine when driving.

I have a call out to the dealer today and I'm sure they'll work with me to resolve, but I thought I'd check here to see if anybody has experienced any of these issues, specifically the P2099. My dealer has been great to work with, but they're about 2 hours away so not looking forward to multiple trips back and forth to get this sorted.

Did you receive the trickle charger from Lotus on delivery? Some people have found that a low battery charge will effect some parts of the car and set off a check engine light. Maybe try fully charging your battery and see if this helps at all. Worth a try before having to drive 2 hours to dealer

 

[morphious]

I hear you on the 2 hour trip thing. I am in the same boat. A CEL just popped up today, and I have been having intermittent failure to start issues. I want it addressed but to the dealership and back is a half day round trip for me.

What are your failure to start issues, it has happened to me 3 times.

 

[alxcrlsn]

Did you receive the trickle charger from Lotus on delivery? Some people have found that a low battery charge will effect some parts of the car and set off a check engine light. Maybe try fully charging your battery and see if this helps at all. Worth a try before having to drive 2 hours to dealer

I don't think I received a trickle charger, but I haven't cracked open the tire repair kit to confirm. I do already have one that connects with alligator clips. I was tempted to disconnect and reconnect the battery, but I'm kind of nervous to touch anything with the battery given all the circuitry they have stacked on top of it, and the warnings in the service manual about disconnecting it. Do you by chance know if the supplied battery is lead acid or AGM?

It looks like in addition to the downstream O2 sensor reading too rich, there's also a pending code of P0174 (System Too Lean - Bank 2). So it's both too rich and too lean, despite the car sounding and driving the same. I'm not very mechanically inclined but my hunch is that the ECU is just having the occasional fit and messing with the fuel trim which is tripping sensors. I assume the dealer ran a diagnostic yesterday when they returned the car to me, so I'm thinking it's likely a sensor/monitoring issue rather than a true engine issue. I'm tempted to try clearing the codes and driving it for a bit to see if they come back, but I don't want to zero out diagnostic data from the car that may be useful for the dealer.

Looking at the diagnostic I took post repair, it looks like the short term fuel trim for bank 2 shot up to 29.7%. Looking back at the freeze frames from my diagnostic before I took it in, the STFT in bank 2 was also at 29.7%. That seems like an awful lot of short term fuel trim, but I'm not sure if it's related to the issues I'm seeing. Running live data from the car and taking it on some test drives, the STFT seems much more reasonable in the sub 10% range.

 

[Blackthought_]

My car didn’t through the 2099 codes but it threw the below. Interesting your dealer said it was o2 sensors. My dealer replaced all o2 sensors and all cats and the car had been good ever since. It’s been 1500 miles since.

 

[alxcrlsn]

My car didn’t through the 2099 codes but it threw the below. Interesting your dealer said it was o2 sensors. My dealer replaced all o2 sensors and all cats and the car had been good ever since. It’s been 1500 miles since.
View attachment 47898

Thanks for the data points. Glad to hear yours is sorted. Thankfully everything seems to just be tied to Bank 2 for me. I’ve been thinking it’s sensors but I suppose it could be the cat as well.

 

[Jjrho]

Having the reduced accel msg n rpm limited to 4k.... drove in 95F + weather up the mountain n it's happened 2x...it goes away after cooling n restart the engine...

What is the final fix ?

 

[Jjrho]

Well, it happened again.... very hot weather n going up the mountain at brisk pace..... about half way to around 3500ft, it goes into limp mode again.... after I come back an hour later, its all good n it doesn't happen again as I'm driving down the mountain..... annoying cause the other guy then catches upto me....

'24 h yellow

James
So.Calif

 

[alxcrlsn]

Quick update, after swapping the O2 sensors, tracing all the wiring, and running diagnostics, the dealer replaced the ECU as the issue kept coming back. I got it back from the shop last week and am test driving now, but hopefully the issue is finally resolved.

My understanding of the issue is that the car was adjusting itself as expected with short term fuel trim, but that the short term fuel trim was permanently too low (-30). So it would fluctuate up and down as needed, but would generally always be too lean for a given scenario.

 

[BVGENT]

I have had my Emira for two weeks, drove from Phoenix to San Diego and back cruising at an easy 75-80 mph to help break it in. Now just over the 1,000 mile break in and the engine emission warning light is constantly on amber. Car is parked until dealer gets back to me. Sounds like this is a recurring problem in these cars. I thought by now the Toyota motor would have all of the kinks worked out.................

 

[Blackthought_]

I have had my Emira for two weeks, drove from Phoenix to San Diego and back cruising at an easy 75-80 mph to help break it in. Now just over the 1,000 mile break in and the engine emission warning light is constantly on amber. Car is parked until dealer gets back to me. Sounds like this is a recurring problem in these cars. I thought by now the Toyota motor would have all of the kinks worked out.................

Put an obd2 on it to see the why. Likely bad o2 sensors

 

[alxcrlsn]

I think there have been some teething issues related to emissions compliance. My understanding from what I've seen online is that there were production delays with the Emira, and in that time California CARB compliance requirements changed. My guess is that the team at Lotus probably had to scramble a little bit to meet the updated CARB requirements, leading to some not-quite-fully-baked emissions systems.

For me, I don't think the O2 sensors were actually the issue though they were replaced. The trouble codes indicated out-of-range readings from the O2 sensors, but that's because what they were picking up (correctly) was in fact out of range. Ultimately, replacement of the ECU appears to have fixed my issues. Worth noting that while the problem was irritating, it was all covered under warranty without hassle and my dealer, Lotus Denver, did a really good job keeping me up do date on the repair, shipping of replacement parts, etc.

 

[Hell4Leather]

My car didn’t through the 2099 codes but it threw the below. Interesting your dealer said it was o2 sensors. My dealer replaced all o2 sensors and all cats and the car had been good ever since. It’s been 1500 miles since.
View attachment 47898

What scan tool are you using and which phone app?

 

[cdn_alien]

The Emiras seem to be spitting out all kinds of faulty codes. Mine is giving me a U0121 code (lost comm to ABS sensor). I had it checked out at the dealer and they couldn't find anything wrong, so they cleared the code and sent me on my way. The car has since thrown this code on at least five other occasions, sometimes the very next day, sometimes a month later since the last occurrence. Always to the same code. So, I just clear the code using my OBDII, and chalk it up to Lotus ownership Mine is an OBDLink MX+

The Lotus dealer where I bought the car from said that it might need an ECU update. Since my Emira has been trouble free otherwise, I think I'll wait until my one year service before doing that (fingers crossed).

 

[alxcrlsn]

Welp, spoke too soon. Just picked up the classic P2099 again, as well as P2272, P2273, and P0451.

I’ll get it back to the dealer next week. The journey continues

 

[RyanGphoto]

I know this is a little bit of an older thread, but just curious....

I have a check engine light on occasionally that resets here and there.. I need to find out what it is.. but what can bad o2 sensors do to the car? Can we use the car with very little issue with bad o2 sensors?