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Still finding my way |
That code denotes the O2 levels in the exhaust stream are different than what the computer thinks it should be seeing. Here is what I have found to be the cause of this code 90% of the time and is an easy DIY fix anyone can perform if you're mechanical enough to change your own oil. Find your MAF sensor. It's upstream from your air filter before your throttle body and is usually fastened in by a couple of little torx screws. Remove it after unplugging the connector and look for two little fine wires inside. Clean them with brake/carb cleaner and use gentle pressure from an acid brush if necessary. Your light should go out and you may notice better throttle response and power. What happens is the computer uses electricity to heat these wires. It measures how much current it requires to keep them at a certain temp (more air flow = more cooling thus more current required). When these wires get contaminated with dust or oil they will become insulated and the computer will think there is less air coming into the engine so it will also decrease the fuel output leading to a severe lean condition. It should look like this.   I do this to my personal vehicles about once a year as preventative maintenance. | |||
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| His diet consists of black coffee, and sarcasm.  |
Pretty much. Not many independents do PCM reflashing. I never have myself. Of those that do, they might have to purchase software from Toyota - if Toyota makes it available - for a one-time use. Because this is one-time use, they are justified in charging you for it, on top of the labor charge. Sometimes if a PCM is flashed they will put a label under the hood somewhere. It could be anywhere, so look carefully. . | |||
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| Team Apathy |
As an update, the code has not returned since clearing itself. I’ve been holding off doing any troubleshooting until such time that the code has returned. | |||
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| 7.62mm Crusader |
Good advice but it is better to buy the spray MAF sensor cleaner in a spray can. Its better for the sensor. | |||
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| Shit don't mean shit |
Timely thread. My wife's 1998 4runner with a 3.4 V6 has had the check engine light on for a few months now. I had the auto parts store get the code (P0171). Reading online I found it could be a couple of culprits. I replaced the upstream O2 sensor, no change. I was going to buy a new MAF sensor, but they are around $150 for a Denso. I read several posts where folks said to clean them. I picked up a can of CRC MAF Cleaner, took the intake plenum off, took the MAF sensor out and sprayed it with MAF cleaner. About a 15 min job. It was really down on power and ran like shit prior to the MAF cleaning. Runs as good as new now! I did a complete tune up to it last month trying to clear the code, which didn't work. 198,500 miles now. Hoping to get another 100k!  | |||
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