Tip & How-To about Cars & Trucks

Engine Light stays on, on a 2002 Toyota avensis 1.8VVI

Normally when the engine light comes on and stays on it's because the exhaust sensors are choked up/dirty. You can take them out heat up the tips then quickly immerse them( the tips) in cold water,this shocks the coating into falling off(do not scrub or wire brush it off). Or for a quick temporary fix you can disconnect the positive terminal of your battery for about 5/6 seconds or wait for the beeps to stop then reconnect. this will reset the computer and clear the fault codes. the result is the engine light comes on as normal when you switch on the ignition and go's out as normal when the engine starts running. works for 1 to 5 days..

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How do you check an 02 sensor on CTS 04 Cadillac 3.6L


If you remove the sensor from the exhaust pipe, measure the element if it a heated sensor. It should give a reading of 3 - 6 Ohms. Measure the voltage from the sensor wires and when heated with a blow lamp the reading should increase with heat. If it does, it is probably OK.

Jul 12, 2017 | 2004 Cadillac CTS

1 Answer

0420 AND CHECK ENGINE LIGHT STAYS ON


DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.

You will likely not notice any drivability problems, although there may be symptoms.

A code P0420 may mean that one or more of the following has happened:
Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
******** spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings

Some suggested steps for troubleshooting a P0420 error code include:
- Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
- Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
- Inspect the downstream heated oxygen sensor (HO2), replace if necessary
- Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

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Feb 17, 2012 | 2000 Toyota 4Runner

2 Answers

Will start but it won't stay on once I step on the


not getting air or exhaust ....its being 'choked'

Nov 01, 2011 | 1989 Jeep Cherokee

1 Answer

how do i repair a p0420 on a 2001 buick lasabre? this is what the check engine light is saying.


Causes A code P0420 may mean that one or more of the following has happened:
  • Leaded fuel was used where unleaded was called for
  • An oxygen sensor is not reading (functioning) properly
  • The engine coolant temperature sensor is not working properly
  • Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
  • Retarded spark timing
  • The oxygen sensors in front and behind the converter are reporting too similar of readings
Possible Solutions Some suggested steps for troubleshooting P0420 error code include:
  • Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
  • Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
  • Inspect the downstream heated oxygen sensor (HO2), replace if necessary
  • Replace the catalytic converter
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Jun 17, 2011 | 2001 Buick Regal

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