Question about 2002 Chevrolet Monte Carlo
Engine light comes on , check with scanner and comes comes up on scanner po 420 bank 1
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Posted on Jan 02, 2017
SOURCE: ERROR CODE
it means you have a bod O2 senser the front one as your car has two or three for a v6 but it will be the first one one in the pipe on the front side of a gm product or if your exhaust pipe comes off the back i.e. 2.3 it will be the one in the manifold itself ohh do not forget to check the plug first sometimes an over enthusiastic mechanic unplugs or tampers with these to get you to do more work check the plugs well and wires they are easily fixed
Posted on Jun 14, 2008
SOURCE: 2004 chevy aveo that the
P0128 - the thermostat may be stuck open or has anyone
put a colder thermostat in the car,because once it starts to get cold
it will throw a SES with a colder then stock thermostat. Replace the Thermostat should fix this problem.
PO700 is a code telling you there are codes in the TCM of some late model cars where the Transmission control module has been removed from the PCM the vehicles main computer , and basically it happens when the TCM has a issue within itself or the transmission that sets a code and it sends a request for the PCM to illuminate the SES or CHECK engine light. To get at the TCM codes requires in most cases the most up to date scanner software purchased after the cars model year and as of yet is still a little iffy. Standard OBD11 scanners will generally not be able to see these codes.
P1781 is set during engine start up when the ECM & TCM do not communicate properly during initial power up. It will only illuminate the service light if the condition occurs in 2 consecutive start cycles, but the DTC will be stored in the failure records after the first cycle.
Replace the Thermostat and go to a transmission shop that can read the DTC codes with a scanner and reset the ECM for clear the codes. Most Transmission shop will do that free of charge, if not turn the Ignition key's to the on position and and pull the ECM fuse out for 30 seconds and then place it back in. Turn the ignition keys to the off position for 10 seconds and then start the car, the engine may stall but let it. Just start the engine again, the ECM is just relearning the engine and go for a test drive. This will clear all the DTC history in the ECM like the day it cam off the assembly line. Good luck and keep me posted, be glad to answer ay more question.
Posted on Oct 30, 2009
SOURCE: PO420 CATALYS INEFFICIENCY BELOW
The PCM copares switch rates between the front O2 sensors and the downstream catalyst moniters. The catylist moniters are often mistaken as O2 sensors, and they are, but that is not their job, or what they are called.
By comparing the switch rates between the front (before cat) and rear (downstream of cat) the PCM knows if the cat is affecting the exaust, and how much it is affecting the exaust.
If it sees little or no effect o the exaust gases that have passed through the cat, then it decides that the cat is not working anymore, and sets a P0420, or a P0430, depending on which bank it is.
To check this yourself, you will need to bring up data stream on your scanner, watch the upstream and downstream O2 parameters and see if they are following each other closely.
If the cat is working right, you should see a fairly rapid switch rate, probably 5 or 6 times a minute on the front O2, but almost a flat line just above .5 volts on the rear. If the rear is switching often you proabably need a catalytic converter.
You can try resetting the ECM by turning your ignition to the on position (engine not running) and pulling the fuse to your ECM for 30 seconds and then placing it back in. Once the fuse has been reinstalled, start the car and let it idle for 1 min and then go for a test drive.
The engine may stall when you restart it, let is stumble and stall. Just restart it, the ECM is relearning the sensors like it was the first start up the engine ever had then go for a test drive.
This should reset everything and turn your check engine light off, if the check engine light came back on, have it scanned again at Auto Zone, Parts source where they scan free of charge and address the issues the DTC codes points out.
The easiest thing to do first is a visual check of things. Visually inspect the exhaust system for leaks, check the catalytic converter for dents, holes, severe discoloration, and check for a rattle inside. If any of those syptoms are there, the converter likely needs replacement.
Then, visually inspect the downstream O2 sensor (behind the converter). Check for broken wires, obvious faults, etc. If all that checks out, you'll want to check the operation of the O2 sensor. To do that, you'll need access to a scan tool or oscilliscope. Check that the waveform is pretty steady. If the reading fluctuates then the sensor is likely bad and will need to be replaced as mentioned earlier.
Thank you for using Fixya and be safe.
Posted on Apr 18, 2010
SOURCE: check engine light code is
There is not a problem with a sensor there is a problem with the catalytic converter. P0420 sets when the downstream o2 sensor is either reading higher than expected or reading simular to the upstream O2 sensor. Either way it is usually the catalytic converter that is the source of the problem and rarely the downstream O2 sensor.
The Catalytic converter is located in the exhaust system under the car. Catalytic converters from either the dealer or a quality direct fit part from a reputable manufacturer are recommended. Cheap cats lead to lots of problems!
Posted on Feb 13, 2011
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