Check Engine Light

[lepa101]

I have cold air intake and header with cat back exhaust. Wondering if that might have anything to do with it. All fluids are good. I just bought car yesterday and everything seems to be fine.

[navylife59]

header cause you got rid of the primary cat. You will have to use the 2 anti-fouler trick on the bank1/sensor2 O2 narrow band on the s-pipe. Don't forget to reset the ECM afterwards.

[lepa101]

I don't really understand the You will have to use the 2 anti-fouler trick on the bank1/sensor2 O2 narrow band on the s-pipe. Don't forget to reset the ECM afterwards.
thing you mean can you elaborate a little more sorry I just not really familiar with that. Is it something major on the car.

[navylife59]

The 2AZ-FE ECM for the tC has a factory wideband bank1/sensor1 on the oem header w/ cat that measures the A/F ratio. Just before the secondary cat on the s-pipe is a factory narrowband O2 bank1/sensor2 that measures the efficiency of the emissions system so the ECM can fine tune things for MPG and a clean burn. If we had a v6 or v8 you would see bank1/sensor1 and bank2/sensor1, etc. Inline engines only have 1 bank of cylinders.

The anti-fouler trick is already well documented around the forums works most of the time. It pulls the O2 sensor out of the exhaust gas stream to fool the ECM into thinking that the primary cat is there and working for aftermarket headers. Have your car's OBDII/CAN system scanned for the exact codes. It might be something different.

[lepa101]

So I will go to the scion dealer and have it hooked up to the computer and then have them do that sensor thing then right.

[ForBiddeN]

if u do that they may void out your warrenty watch what you do there is a guy on the forums told the dealer what he had and they voided his warrenty. go to a parts store like autozone or adv auto parts they have an obd computer that will tell u whats wrong.

[peruano85]

or just disconnect the battery for about half an hour and it will reset the ECM

[navylife59]

5 mins should do it. It will take some driving around to let the ECM relearn. No big prob, it will just take 20-50 miles to recalibrate to the best performance.

[lepa101]

Yea I'm just putting the stock exhaust all back on, if anyone has the stock exhaust manifold be interested in purchasing it.

[ForBiddeN]

sell me your headers and ill make a trade

[lepa101]

alright sounds good to me. What year is your scion, I have a 06.

[ForBiddeN]

it doesnt matter what year it will bolt on only diffrence in the 07's are some of the electrical work. but 07 lol.

[Moose10]

Hello peeps I need some info on my check engine light that just came on i got the codes read and it reads p 420 can someone tell me what that means, what caused it what needs to be fixed and about how much it would cost please ASAP.

[navylife59]

DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)


MONITOR DESCRIPTION
The ECM uses the 2 sensors, mounted in front of and behind the Three-way Catalytic Converter (TWC), to monitor its efficiency. The first sensor, the Air-Fuel Ratio (A/F) sensor (sensor 1), sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor (sensor 2), sends post-catalyst information to the ECM. The ECM compares the information transmitted by these 2 sensors to determine the efficiency of the TWC performance and its ability to store oxygen. When the TWC is functioning properly, the variation in the oxygen concentration in the exhaust gas after it has passed through the TWC is small. In this condition, the voltage output of sensor 2 slowly alternates between the rich and lean signal voltages (shown in the illustration below). As the TWC performance efficiency deteriorates, its oxygen storage capacity decreases, and the variation in the oxygen concentration in the exhaust gas increases. As a result, the sensor voltage output fluctuates frequently. While the catalyst monitor is running, the ECM measures the signal lengths of both sensors 1 and 2, and calculates the ratio of the signal lengths to determine the extent of the TWC deterioration. If the deterioration level exceeds the preset threshold, the ECM interprets this as the TWC malfunction. The ECM then illuminates the MIL and sets the DTC.

Sounds like your primary TWC is clogged. It is also possible that one or both of your O2 sensors maybe or clogged. Have you used any bad gasoline or used fuel additives? Are you F/I or shoot'n the juice?


Alot of troubleshooting to figure this out. You should take it to the Dealership when ever you can. There is no rush on this unless the engine is running erradict.

[Moose10]

No i havn t i just bought the car actually what should i do to get it fixed ??

[navylife59]

Sorry for the delay, been on a long trip. I suggest that you take it to the Dealership. Unless you have replaced your stock header, it should be warrantied.

[transmetal]

hey man i had the same problem before when i replace the full exhaust sistem and after i put the CAI so hapen 2 times, now when the ligt c- on the 1rst time? that way i know if i can help

[NVeed_TC]

Yea I'm just putting the stock exhaust all back on, if anyone has the stock exhaust manifold be interested in purchasing it.

I have a stock manifold sitting in my garage if you still need 1. Ill give it to you dirt cheap. PM me & well talk.