Question about 2004 GMC Envoy

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Incomplete monitors :catalyst 2004 envoy emmisions fail ?

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After the MIL is turned off or the battery was disconnected for some time, all monitors are set to incomplete. However with several short trips with engine getting at least to hot enough for thermostat to open, (I believe 8 is the magic number of trips) most monitors are set, you may be able to pass the test with only one incomplete only.

Posted on Nov 26, 2014


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I recently reset the obdII error codes on my 2002 Kia Sedona after replacing the 3 ignition coils and plugs and wires to eliminate a problem with primary and secondary ignition coil circuit. Need to k

Replacing Spark Plugs & Ignition Coils
does not require any clearing of codes

You have 8 monitors on most vehicles

5 Monitors do not run all at one time

If the Catalyst fails when it does run, then you
may have not replaced the front O2 Sensors
at 100,000 or one failed
Have to use professional scan tool to look at data
& see if the I/M Monitors have run

The Evap is the last to run & there is no info avail
as to when it runs, as far as I know

The Evap will run once or twice a week-maybe

The cat should run by 50 miles of driving or a couple
hours run time

From 2002 until now-- I doubt the converter has much life left,
but the monitor will still run.

Look at scan tool misfire on Mode $06,O2 Data,Fuel Trim
and such, after a road test of 25 miles,then component test
anything not as it should be.

If you keep using your code reader to clear DATA- forget the codes,then your monitors,freeze frame & such are gone,thus your current situation.

Feb 28, 2014 | Cars & Trucks

1 Answer

Anyone has a grand prix with monitors incomplete for an emmissions test

drive at a steady 50mph for about 10miles after a cold am srart

Jul 13, 2012 | Cars & Trucks

1 Answer

Catulyst monitor and evap system monitor and oxygen sensor not ready also P0501 code

Diagnostic Test Code (DTC) P0501 "Vehicle Speed Sensor Range/Performance"
The Wheel Speed Sensor (WSS) generates a waveform with a frequency according to the speed of the vehicle. The signal generated by the WSS informs the ECM not only if the vehicle speed is low or high but also is stopped the vehicle or not. The ECM uses this signal to control the fuel injection, ignition timing, transmission/transaxle shift scheduling and torque converter clutch scheduling. Also the WSS signal is used to detect rough road driving condition.

Whenever Your OBD readiness monitors cannot complete it is because there is a problem that is affecting fuel mixture, ignition timing, or any other fault that can affect the level of tailpipe emissions. Once these faults are repaired, then the codes must be ereased so that the monitors can run and "re-test" the system to check for the same, or any other faults. The goal is for all the monitors to run and change to "complete" without any fault codes present.

In your case, the wheel speed sensor fault needs to be diagnosed and repaired so that the monitors will complete. Also note that one incomplete monitor can prevent other monitors from running. In your case, the catalyst monitor cannot run because the O2 sensor monitor is not complete. The catalyst monitor can only run AFTER the O2 sensors have received a "clean bill of health" from the O2 sensor monitor. The wheel speed sensor problem is keeping the O2 sensors from being tested.....So the wheel speed sensor problem is pretty much causing the whole thing.

Here's the kicker...If the vehicle has been driven in this condition for a period of time, there may be damage to the catalytic converters. The computer does not know this yet because the catalyst monitor cannot run. So it is possible that you can fix the wheel speed sensor thing, the O2 sensor monitors will complete, then when the catalyst monitor runs it could set a "catalyst efficiency" code. Then you will have to replace your catalytic converter to fix that. I'm not saying that this WILL happen on your vehicle, I am just saying that it CAN happen so you will not be confused IF it DOES happen. I see this all the time, and I have had customers accuse me of doing something to their car so I could sell them a high-dollar catalytic converter. This is simply not the case...I had no way of knowing that the converter had a problem because when I first received the car, the catalyst monitor was incomplete and there was not catalyst code present at the time.

So the only way to do this is to correct ALL fault codes one at a time until all monitors are complete and no fault codes are present.

Sep 17, 2011 | 2004 Hyundai Elantra

1 Answer

Check enging light on 2003 Acura TLS doesn't come on when starting car. Failed emmision test because of it.

There is a problem with your OBDII (Onboard Diagnostics -2) system. The only way to find out why your Check Engine light is on is to scan your engine computer and find out which part of the system is failing. There will be fault codes stored in the computer to tell you. The failing system will then need to be diagnosed to locate the actual cause of the failure. Once this is completed, the computer will have to be reset, and the car will have to be driven (sometimes for several days) to get all of the computer monitors to run and recheck the system. If the repairs are successful, the same codes should not return. You may have new codes show up however. This is because some of the monitors are unable to run if the check engine light is on due to another failure. Sometimes a code like "Catalyst Efficiency Below Threshold" will show up when they were not there before. This is because driving the vehicle with the Check Engine light on has destroyed the catalytic converters, but the code could not set previously because the catalyst monitor could not run to test the catalyst when the other problem was present. Now that the first problem has been corrected, the catalyst monitor now runs and has determined that the catalyst has been damaged.

This why I tell all my customers that the best time to get your car ready for an emissions test, is the minute the Check Engine light comes on. Ignoring this light and driving the vehicle with it on can damage some pretty expensive parts, as well as possibly costing you fines for not getting your vehicle "Legal" when it is time to renew licenses, etc. I live in Missouri, and you cannot renew your license plates without passing the emissions test - people wait until the last day to renew their registration and they get angry with me when I tell them it is going to take several days and possibly even a couple weeks to get their car to pass. It's not MY fault!!! THEY are the ones who chose to ignore the warning lamp!

Feb 06, 2011 | 1996 Acura TL Series

1 Answer

My 2000 saturn sc emmision diognostic result said secondary air system not ready, catalyst not ready, egr system not ready. what's the most inexpensive way to correct these?

someone clearder the code and now the monitors need to rerun,,,you must drive the car and they will reset providing there is no check engine light on,just drive it

Feb 18, 2010 | 2000 Saturn SC

1 Answer

3 codes present on my 2002 Envoy. p0172, p0420, and p0340,

Track the p0340 first camshaft timing is very important and could possibly cayse your other codes,Call your local GMC dealer I think I remember a bulletin about this code.

Aug 21, 2009 | 2004 GMC Envoy

2 Answers

Failed emmisions test..

I am in Virginia but I believe you vehicle is showing a monitors not ready for Catalyst & Evap. If that is correct you need to basically drive the car a few days. The computer will remonitor itself and should be fine following that. Most drive cycles require highway driving & city driving. Make sure you turn on a/c as well. Its not how many miles you drive but what conditions you drive that sets you monitors. You could locate the drive cycle and attempt to replicate it but its usually very difficult drive exactly as the cycle asks. Good luck.

Mar 18, 2009 | 2003 Mercedes-Benz CLK-Class

1 Answer

Monitor Reset

The following conditions must occur to complete a Trip and test all OBD II monitors and components including the Catalyst Efficiency Monitor:
-- The misfire, comprehensive component, and adaptive fuel monitors are checked continuously from engine warm-up and can complete any time.
-- The exhaust gas recirculation (EGR) monitor test requires a series of idles and accelerations.
-- The heated oxygen sensor (HO2S) monitor requires a steady speed drive for approximately 1 minute at 30 to 40 mph.
-- The catalyst efficiency monitor requires a steady speed drive for 1 minute and 20 seconds beyond the HO2S monitor test at 40 to 65 mph.
If you cut engine off before test are completed then you must wait for a 6 hour cool down before monitors will run again.

Feb 06, 2009 | 1996 Nissan Quest

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