Toyota Tacoma Diagnostic Codes and Warning Lights

jsouzajsouza Member Posts: 2
edited August 2015 in Toyota
My check engine light came on so I took my truck to the deal to find out why.

The diag codes that came back were: P0402 EGR and P0420 CAT.

The truck is running perfectly.

They are telling my that for the P0402 code I need a new EGR and EGR module, which with labor is about $400 - $500 to repair.

The other code will be much more expensive and with the EGR will probably cost about the same as the value of the truck. They are saying I need a new front convertor, rear convertor and an O2 sensor (O2 sensor was replaced 2-3 years ago). This will run about $2700.

I do not understand the CAT and EGR issues since the truck is running absolutely find; no abnormal exhaust smell.

Toyota tells me that a 3rd party exhaust service station can fix the CAT issue for probably a third of the cost with after market parts.

I've tuned up the truck (new plugs and air filter) hoping the problem is just poor airflow or a miss-firing plug. The engine light is out since Toyota ran the diag but if there is a real problem it will come back on.

Can anyone help me understand what these codes really mean or could also mean?

See also: What Your Check Engine Light Is Telling You


  • marcusxmarcusx Member Posts: 22
    Read what it says here under possible solutions:
    "With a P0402, it is common for people to replace the EGR valve, only to have the problem return. The most likely solution is to replace the DPFE sensor."

    For the other code, read here.

  • bill1840bill1840 Member Posts: 2
    Hi, folks. Can anyone tell me where the Tacoma OBD II port is located in the vehicle (2000, 4 cyl.) Thanks. Bill
  • plm2plm2 Member Posts: 3
    Hi Bill Most all OBD II conections are located on the divers side under the lower dash panel.It is a 16 pin con.
  • jojiejojie Member Posts: 2
    if it's running fine then it's probably just the O2 sensor
  • pandesalpandesal Member Posts: 4
    Does anybody know how to get rid of the Maintenance required light?
    I have a 2007 double cab tacoma and my maintenance required light came on. Since I did not have time, the light came on and I only chnaged the oil after one week. I just changed the oil and the light is still on.
    I red the manual and says reset the ODOMETER.
    If I reset it, is it going to stay to zero again?
    Anymore ways of ressting it?
  • pandesalpandesal Member Posts: 4
  • fiddycentfiddycent Member Posts: 8
    You can go to Advance Auto and borrow their obd tool and clear the codes yourself or just disconnect the battery for about ten seconds and then re-connect it. If your truck has an alarm, make sure that you have the key fob device handy. Things get real loud, real fast. Getting the obd tool is the preferred method as it lets you see what codes are stored rather than just erasing them.
  • klodgeklodge Member Posts: 1
    My 2000 Toyota Tacoma (4 cylinder) seems to run perfectly, but the Check Engine lamp illuminated about 2 days ago.

    I have followed diagnostic instructions carefully and I am perplexed at the results. The diagnostic instructions from a Toyota website that I am following are:

    "...Later models, '87 and newer use a multiple terminal "DIAGNOSTIC" connector which is a small, rectangular-shaped gray "box", usually located near the right fender in the engine compartment. To get codes out of this type of connector, jump the "TE1" and "E1" terminals. Finding these terminals is easy as the inside cover of the diagnostic connector contains a schematic of the connector pinouts..."

    When I insert the jumper (paper clip) between TE1 and E1 then turn the ignition key to ON, the Check Engine light illuminates and stays constantly illuminated (e.g. the check engine lamp doesn't change intensity). I have waited over 3 minutes and there are no changes.

    I have also disconnected and reconnected the jumper with the ignition switch remaining in the ON position. The results were exactly the same.

    I have reset the ECU by disconnecting the battery and the check engine lamps stays out for about 15 minutes of driving, but then comes on again.

    Does a steady Check Engine light have any meaning?

    Can you provide any insight into what the problem might be?

    Ken Lodge
  • toyotataco03toyotataco03 Member Posts: 2
    Everytime i press the brakes my right turn signal lights up but does not flash, the signal works normally when the brakes are not pressed
  • LeoRiveraLeoRivera Member Posts: 2
    to get rid of the maintenance light- put the key in the ignition and turn it to the on(all the warning lights turn on but dont start the engine) position, click the button by the odometer until the mileage of your truck comes on. hold down the push button and turn the key to the off position, still holding the button, wait about 10 secs, keep holding the button, turn the key to the on position(all the warning lights turn on but dont start the engine) you will see 4 or 5 dashes on the odometer, wait till they dissappear. thats it, release the button.
  • vu90gvu90g Member Posts: 1
    Thanks Leo! Worked like a charm.
  • tbertontberton Member Posts: 1
    I have a 2006 tacoma and when I start the engine the maint light comes on and blinks six times, then it goes off. I don't have to crank the engine I can just turn the key to the start position. Truck runs great, have 40,235 miles. Also can you check the codes but turning them on with the truck functions. Like turning the key when you cancel the oil lihgt.
  • toyotaco04toyotaco04 Member Posts: 2
  • toyotaco04toyotaco04 Member Posts: 2
    i kno its an o2 sensor if i dnt change it can it harm anyhting in my vehicle and when the obd2 pulled it up this is what it read "p2238 02 bank1sensor1 positive current circuit low " plz give me some info and any idea how much a sensor is and is it hard to replace and also where is it located? thanks alot
  • bdn1bdn1 Member Posts: 1
    I have had this annoying check engine light that will not go away. I recently changed both the up stream, and down stream O2 sensors. When the engine had to be re-built I added a NWOR Header, Volant cold air intake, and JBA cat back exhaust. I also changed out the cat at the time of the re-build due to the engine over heating a floating the head gasket, and seizing the rings. The truck runs great, I average about 24 mpg on the highway, and have no other problems. When the computer is scanned it come back with a catalyst code. Any ideas out there on a possible fix for this?
  • jcsouzajcsouza Member Posts: 1
    2001 Tacoma's Check Engine Light came on right before I took it for the state inspection. My mechanic was good enough to give me the code printout that reported "System Too Lean" and "Air/Fuel Ratio Sensor Circuit range" They suggested the thermostat which I cahnged with no effect. I'm now way out of date for inspection and need to renew my registration, guess I need an answer.
  • mmasoodmmasood Member Posts: 1
    On my 2002 Tacoma twin cab, I have code P0442.
    Somewhere there is a leak in my evaporative syst.
    How do I find the leak?
  • vitiervitier Member Posts: 1
    The check engine light in my toyota tacoma ( 2002 3.4 l auto trans ) is on. I bought OBD 11 PocketScan to read the codes , it had one code ( P 1135 = manufacturer control fuel air metering ) . I have no clue what this means , maybe someone those . thank you Rick .
  • rmreidrmreid Member Posts: 2
    Did you ever find out what was causing this problem? I have the same thing except it is the left side.

  • jamsonjamson Member Posts: 1
    Hi, I really hope someone can help me with this problem. My 2000 tacoma starts very difficult. Sometimes it doesnt even start. The engine turns over but only occasionally will fire. This problem has gotten worse since the cold weather last fall and has progressed over the winter. I usually get it started by bump starting it at which point it will not stay running unless I stay on the gas pedal. Once I drive the half an hour to work it will usually start but not always and it still is very hard to start. I really have to let it crank until it fires. The check engine light has been on and off intermittently but has remained on for the last month. One more thing, when it is cranking over and starts to fire, it does not always start, it will kinda backfire. Not a full on gunshot backfire and there is a strong gas smell. If it had a carburetor I would think it would be flooded. Has anyone else out there had this problem and if so what was the fix? Please help cause I do not want to get ripped off by the dealer if this is an easy fix. Thanks in advance.
  • elaine67elaine67 Member Posts: 1
    Hello, my 98 tacoma has the check lamp light on. The manual told me to make sure that the gas was full and that the gas cap was on properly. They both are. It then said that it's something electrical, but didn't seem urgent. Can I wait a few days before taking it to the shop or should I go immediately? Thanks, Elaine
  • duck32_2000duck32_2000 Member Posts: 1
    I had the same code come up on my 02 2.7 liter tacoma, i replaced the air-fuel sensor located in the exhaust pipe in front of the catalatic converter,its a little costly ,but, it solved my problem.One other thing before i began working on my truck i disconnected the ground cable from the battery, then reconnected it when i was done it cleared the code and the check engine light went off,also it would be wise to do this repair work on a cold engine. good luck.
  • gladtohelpgladtohelp Member Posts: 1
    I too have a check engine lightproblem with my 2000 tacoma. I found that it turns on and off each time I purchase gas. A mechanic in Ann Arbor , MI replaced a fuse in the fuse box under the hood. I don't remember which fuse it was bit i think it was the second or third from the bottom or side of box toward front of vehicle. He said the Tacoma has a prob;em with this fuse becoming fowled when one gases up. When fuse replaced the light goes off.
  • damonericdamoneric Member Posts: 1
    edited May 2010
    i also had some similar issues with my chevy and after looking at my chevy engine codeswas able to pinpoint the problem. although i still think i might visit the dealership once to show the problem.
  • jackie58jackie58 Member Posts: 2
    edited June 2010
    My truck was starting hard each time, worse on a cold start, diagnostics said it was the crank shaft sensor, had that replaced, it started better but not right for about 3 weeks, now it won't start at all. Had to use starter fluid this morning. the crank shaft sensor is still coming up on the diagnostics. we are thinking it could be something electricial to cause the crank shaft sensor to not work properly...I have had a tune up within the past 16 months so all that should be good. Any suggestions
  • jackie58jackie58 Member Posts: 2
    jamson...I've got about the same problem right now with my 2000 tacoma, did you finally find a fix?
  • longbow713longbow713 Member Posts: 6
    Check engine light came on about 8 months ago.
    Code says improper flow through sonverter.
    I had converters and sensors replaced, problem went away, and returned few months later.
    Plugs, plug wires, converters, up and down stream sensors are all new. Light is back on.
    When I had it reset, it came back on after about 100 miles.
    I replaced battery and light came back on after about 1,000 miles.
    Light is still on, truck runs perfect with no change in mileage or performance.
    The code is always the same, converter flow.
    I have inspection this month, any thoughts?
  • peacockangelpeacockangel Member Posts: 2
    What was the mileage when the CEL went on?
  • longbow713longbow713 Member Posts: 6
    Thanks for the reply. I had about 120,000 miles when light went on. Truck runs great, just high miles and #$%^ engine light.
  • peacockangelpeacockangel Member Posts: 2
    I was wondering if you had replaced any of your tires shortly before the light went on. basically I had the same thing happen, mine at 162,000 miles. About a month before I had replaced 2 tires. Other than the light, the trucks run great.
  • jbeatonjbeaton Member Posts: 2
    Just did it on my Tacoma. You must ensure that the odometer is displaying on your instrument panel. It must say ODO. Turn you key off, then depress the odometer reset button and hold. While holding, turn key to on position (with instrument lights displayed) but do no start. You should see the Odometer count off some dashes and then end with several zero's in the display. Once you see that, release the reset button and then turn the key off. Go ahead and start the vehicle, and the Maintenance Light should be off
  • jbeatonjbeaton Member Posts: 2
    Where is the Diagnostic Connector located on a 2010 Tacoma?
  • bellwbellw Member Posts: 1
    If this is the right forum but i own a 2006 toyota tacoma and 2 new sensor light have turned on one is like red that looks like an antenna!Help anyone!Thanks in advance :confuse:
  • jshrumjshrum Member Posts: 1
    I have 99 tacoma with 210k+ miles and just last week check engine light came on. Auto Zone checked it and code 420 came on. I need any help I can get with this, bought truck new and it has been best vehicle I have ever paid for.
  • bullydog4bullydog4 Member Posts: 1
    had intermediate exhaust replaced 2 days ago. engine loud still and check engine light is on. gonna take it back to repair shop, but wondered what could be going on. (1999 4wd 2.7L)
  • dporterhousedporterhouse Member Posts: 1
    I have a 06 Tacoma with 230k+ miles on it the check engine light came on for the cat, got secondary cat replaced and light didnt come back for around 200 miles. hooked up obII comp and came up with code P0420. the o2 sensor is being lazy and not reading as it should. buddy of mine who did the aftermarket cat says its the 02 sensor but another buddy who is also mechanic says that the secondary cat wasnt only problem and should replace the other cat. lemme know ideas and next step thanks
  • daveschottdaveschott Member Posts: 1
    Whats up with all these check engine lights... My 02 Tacoma did it at 30,000 and it was the 02 sensors ... now it doing it again at 69,000 That's hardly no mileage at all is it the gas or lack of [ meaning ethenal in the gas ] What is the problem with the gas we are buying and these O2 sensors going bad in 30,000 miles..... Dave in Fl.
  • davefromncdavefromnc Member Posts: 1
    Awesome! This works---Fantastic Glad to get rid of that light--I do all my own oil changes. Thanks for your help.
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