I have a 2000 Toyota Corolla with just over 110,000 miles. The car runs well, but the check engine light came on about 6 weeks ago and the mechanic says it is the code for a lean condition. By now we have replaced both the forward O2 sensor and the mass air flow sensor. The light stays off for 2-3 days after each of these repairs and also twice after the light was turned off by momentarily disconnecting the battery cable. On one occasion the car was driven 350 miles (mainly highway) before the light came back on. It is possible that the light is more likely to come on after filling up the gas tank since that was done the day or day before the light came back on. Since it starts well and runs well, where should one look next?
What is the exact code numbers you have not ode descriptions? Also has the fuel pressure been checked?Has a smoke test been done to see if you have any vacuum leaks?
August, 22, 2013 AT 5:12 PM
Thank you for the reply, I will ask the mechanic for the exact code(s). The mechanic claimed no leaks but I do not know how he determined that. I do not think the fuel pressure was checked.
August, 22, 2013 AT 5:16 PM
The best way to look for leaks is with smoke most people don't use smoke. But smoke will fond the smallest leak and leaks that are in tight places.
September, 4, 2013 AT 7:06 PM
Although I have not yet had a smoke test, I have noticed that if the Check Engine light is turned off by momentarily disconnecting the battery cable, then it tends to stay out until just after the next time the gas tank is filled. The last time the light came on minutes after filling the tank and driving out of the gas station. Maybe this is another clue. The gas cap was replaced just recently with a brand new one from the Toyota dealer, after this problem started.
September, 4, 2013 AT 8:29 PM
You never did say what the exact code number that is setting?That would really help out a lot.
September, 13, 2013 AT 12:37 PM
I purchased a code scanner (OBD II Pocketscan) so I could get them without going back to the mechanic. The light stayed out for 8 days (including during a 500 mile round trip) but then popped back on. The code is P0171 and then a second P0171 that has a symbol that says it is 'pending'. For monitors, 1 is designated as 'incomplete' and it is noted as EVAP. The others (MISFIRE, FUEL, COMP, CATALYST, O2SNSR, and 02 HTR) list as ready. It also says MIL is 'ON'. That is all the information that the device reads out. Car still starting and running great.
September, 13, 2013 AT 12:45 PM
If the fuel pressure is good we need to smoke it and see whats going on. So does the light come on when the engine is cold or hot?
September, 13, 2013 AT 12:47 PM
Are you good at building things?I built my smoke machine out of spare parts and a new glow plug.
September, 13, 2013 AT 2:31 PM
It has come on after having driven as little as a mile or two, after about 5 miles, and once right out of the driveway. If it is out and the car is being driven tens/hundreds of miles it tends to stay out. Maybe that would be considered as coming on when 'cold' and not having driven too far. Out means I have turned it out by momentary battery cable disconnection.
September, 13, 2013 AT 2:54 PM
Then I would smoke it when cold. So are you good at building things?