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 r red used accel nsg 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 ?