Overall, it took me about 6 hours to pull it apart and then put it back together. Also, if after rapid accelerator kick down, then there must be really wrong with the exhaust leak, or lack of indicated fuel. You could get that diagnostic check done and see if they can tell you for sure if it is the cat or O2 sensors. I do notice occasionally when at a red light, the idle drops down a little close to 0 and then jumps back up to normal, a little below the 1. If the P0421 code is combined with other codes, try fixing the other codes first.
Don't replace all of it if you don't have too. If the visual test checks out, the mechanic may then move on to testing the oxygen sensors and the powertrain control module starting with the sensors. Common Misdiagnosis The most common misdiagnosis is caused by not thoroughly investigating what led to catalytic converter failure. About six months back I had ignition problems that were hit and miss on my 2002 model, all stock. Any other feedback is welcome since it will be another week before I can get it to the shop.
The first time the shop said that if it came on again, take it to the dealer due to the 8 yr emission warranty. I'm not trying to be an ass here, but I'd do the following: Listen to what TheMan says. This will turn the check engine light off and then you will know if the check engine light returns, you've got further diagnostics to complete. Inspect the tailpipe, especially following start-up. If the P0421 code was the only code stored in the system, the mechanic may begin diagnosing this issue by taking a look at the exhaust system. P0421 code on vehicles with electronically controlled automatic transmissions, the 3-4 shift solenoid is responsible for actuating the hydraulic circuits to activate clutches or bands that change gears inside the automatic transmission. How serious is the P0421 code? I cleaned the air flow sensor.
The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing. I will bring this with me: If you have valid warranty claim, you cannot be charged for any costs associated with the diagnosis or repair of the problem, including labor charges, parts, or miscellaneous items that are necessary to complete the repair. Do you have any suggestions or ideas, or anything else to try in reference to my situation. Positive digits may means the computer is adding fuel, while negative digit means it is removing fuel. One thing I tried was to remove both O2 sensors and spray them with Carb cleaner to see if that helped. Then, idle smoothness: check for signs of roughness or surging, as they may indicate engine misfire or wrong delivery of fuel. Car runs perfect and gets 30mpg.
If the sensor shows low to no voltage, this means the sensor could be defective. The P0421 code can be very serious. If you know where the sensor is, you only have to unclip the old sensor and replace it with a new one. Question is: Is the cat damaged from the misfire? Now don't ask yourself; What should you do with P0421 code? As I pulled in it stalled on it's own. In the afternoon I got in it and the idling issue was back and car had same issue where I could barely get any power and car is bucking, check engine light flashing again. I've had the P0421 warm-up catalyst system below threshold code pulled from my car twice. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar.
Again, if your car has the same setup as mine, there are 2 Cats. P0421 Audi Description The Engine Control Module monitors the switching frequency ratio of heated oxygen sensors 1 front O2 sensor and heated oxygen sensors 2 rear O2 sensor. They want to know what the problem is. The best thing to go at this however, is to fix the problem first, before replacing the Converter. Although this is the most likely cause of a P0421 code, it is not the only cause, and every other possibility should be ruled out before replacing any parts. She didn't hit very hard- mostly scs along the quarter panel. I changed the spark plugs.
If the engine is running efficiently, the upstream O2 sensor will cycle regularly from one-millivolt. If the P0421 code is combined with other codes, try fixing the other codes first. Sensor 1 is located before the converter, Sensor 2 is right behind the Converter, Bank 1 and 2 in V-configuration where Bank 1 is on the side Cylinder 1 is located. Spent engine exhaust gases are pushed through the exhaust manifold, into the exhaust pipe, over the upstream O2 sensor, through the catalytic converter, and they pass over the downstream O2 sensor. If it is the cat bad they are under federal warranty for 80k or 8 years.
You could get that diagnostic check done and see if they can tell you for sure if it is the cat or O2 sensors. When the frequency ratio of heated oxygen sensors 1 and 2 approaches a specified limit value, the three way catalyst malfunction is diagnosed. Write this information down because it may be helpful if this proves to be an intermittent code. Catalytic converter efficiency is monitored using upstream and downstream oxygen O2 sensors. This holds especially true when considering that the catalytic converters are usually the most expensive part of the whole exhaust system.
With a P0421, I would begin with a visual inspection of system wiring harnesses and connectors. Warm Up Catalyst Efficiency Below Threshold Bank 1 Basically this means that the oxygen sensor downstream of the catalytic converter on bank 1 is detecting that the converter is not working as efficiently as it should be according to specs. Without checking the engine light and I finally did in the end, I guessed many times. Read the scan data list when the engine runs and at its operating temperature. The solution is here : P0421 Possible Solution: Gasoline engines use spark plugs to cause an explosion of fuel within the cylinder. The P0421 code can be very serious. This is the rear sensor, or the sensor next to the converter.