99 Suburban ready codes

[gorent]

I have a 99 Suburban with 350 gas engine and am having an issue with five not ready to test codes not reducing or going away even though I have not had a "MIL" light on or cleared any pending codes in several months. I have cold started engine many times and driven many miles since last clearing codes and see no changes in not ready codes clearing. The inspection station told me to disconnect positave battery cable for 1/2 hour and reconnect and still I saw no changes.With no codes and no pending codes at inspection they still will not run test because there are always 5 "not ready" items showing. Any help would be appreciated! Vehicle runs like a top after replacing Passlok computor several months ago and I wonder if this affected the system?

[maxwedge]

You must mean emissions monitors not codes, any battery disconnect will cause monitors to require a drive cycle to bring them online to pass an emissions inspection. Google a search for GM drive cycle for info.

[gorent]

Battery disconnect and code erase was done over two months ago and I drive vehicle nearly every day to work about 15 miles one way, tonight I gased up to 3/4 tank and drove 40 miles and all 5 monitors still read not ready. That is what I do not understand. I always make sure temperature goes up to themostat opening and drops down on each trip also. I am baffled!

[maxwedge]

Assuming your scanner is working correctly, this is very unusual that all the monitors are offline, I would follow the recommended drive cycle.

[gorent]

The state inspection machine reads the same as my reader also and this has been done several times to be sure. I have been trying the different drive cycles and will continue to do so. None of these seem to read the same, but I will keep trying. Even the State inspector says thi is quite unusual. Thank you for your input and responces!

[j cAT]

Originally Posted by gorent

The state inspection machine reads the same as my reader also and this has been done several times to be sure. I have been trying the different drive cycles and will continue to do so. None of these seem to read the same, but I will keep trying. Even the State inspector says thi is quite unusual. Thank you for your input and responses!

you have given us no info that can help you. so what are these pending / not ready codes that are the issue ?

many times the evap codes do take some time , perhaps the EGR codes. so what are these 5 codes ?

[gorent]

The Ready monitors that never change to Ready are: catalyst,evap,02 sensor,02 htr and egr. Since 8/4 I have cold started vehicle 15 times and put on 562 miles. Today alone I put on 79 miles round trip after cold start and all 5 codes are still not ready. On each cold start I follow the "drive cycle " directions as close as possible. There have been no mil lights or pending codes during this time, nor have I disconnected the battery. Is this enough information?

[j cAT]

Originally Posted by gorent

The Ready monitors that never change to Ready are: catalyst,evap,02 sensor,02 htr and egr. Since 8/4 I have cold started vehicle 15 times and put on 562 miles. Today alone I put on 79 miles round trip after cold start and all 5 codes are still not ready. On each cold start I follow the "drive cycle " directions as close as possible. There have been no mil lights or pending codes during this time, nor have I disconnected the battery. Is this enough information?

with that I would say the PCM is defective or needs a flashing . those tests are in the PCM software . post back how this was corrected not a very common problem.

I would have the dealership re-flash the PCM. then they can determine if the PCM is working correctly. bad grounds and poor PCM connections[corrosion] can mess up the PCM as well as jump starting the vehicle improperly.

[777stickman]

I see you have disconnected the POS batt cable for 1/2 hour. I would suggest disconnecting the NEG batt cable for over nite just to see what happens.

What are the so-called "ready" code numbers. Is this '99 Sub an OBS(Old Body Style) or NBS(New Body Style)?

[gorent]

Originally Posted by 777stickman

I see you have disconnected the POS batt cable for 1/2 hour. I would suggest disconnecting the NEG batt cable for over nite just to see what happens.

What are the so-called "ready" code numbers. Is this '99 Sub an OBS(Old Body Style) or NBS(New Body Style)?

I disconnected negative cable as suggested and when reconnected while warming up the same 5 not ready were still there. I then went tru the recommended drive cycle procedure and all 5 not readies are still there! I have noticed that regardless of which cable is disconnected, only the clock and not the radio need reprograming. I have not disconneced both cables at the same time yet, but have been told by two local Chevy dealer tech's to disconnect both cables and connect them togeather with clamps overnight to correct problem. Does this sound kosher to any of you? I am a little concerned doing this if there is any battery back up in PCM. If this is normal I will try next.

[gorent]

I am bewildered again. As instructed I removed Both (+) and (-) cables from battery and jumped cables together as told for 14 hours and results were the same, All 5 not ready monitors still present and only clock had to be reset. I then took it on another drive cycle run and nothing changed. How is system maintaining power when disconnected? I would assume with both cables off battery that radio would loose programing also, but it does not and when I checked monitors after reconnecting Battery prior to starting they were all the same as prior to disconnect. Does PCM have an internal back up? I only have one battery in vehicle. All reding I have done say's a complete power disconnect should clear all codes and monitors and cause PCM to have to be self reprogramed via recommended drive cycles. I am totally baffled

[j cAT]

Originally Posted by gorent

I am bewildered again. As instructed I removed Both (+) and (-) cables from battery and jumped cables together as told for 14 hours and results were the same, All 5 not ready monitors still present and only clock had to be reset. I then took it on another drive cycle run and nothing changed. How is system maintaining power when disconnected? I would assume with both cables off battery that radio would loose programing also, but it does not and when I checked monitors after reconnecting Battery prior to starting they were all the same as prior to disconnect. Does PCM have an internal back up? I only have one battery in vehicle. All reding I have done say's a complete power disconnect should clear all codes and monitors and cause PCM to have to be self reprogramed via recommended drive cycles. I am totally baffled

what you did is reset the learned engine operation and deleted the PCM testing results of the engine emissions. this does not re program the computer another computer must be connected to your computer to re program the PCM brain. that is if the PCM you have is working correctly.

since you reset your PCM you will need to drive the vehicle 300-500 miles keep the fuel level between 1/3 and 7/8 of a tank and test again for the readiness monitors to have been completed by the PCM...

any battery disconnect you will erase the testing results which is needed to pass the emissions test.

[gorent]

Originally Posted by j cAT

what you did is reset the learned engine operation and deleted the PCM testing results of the engine emissions. this does not re program the computer another computer must be connected to your computer to re program the PCM brain. that is if the PCM you have is working correctly.

since you reset your PCM you will need to drive the vehicle 300-500 miles keep the fuel level between 1/3 and 7/8 of a tank and test again for the readiness monitors to have been completed by the PCM...

any battery disconnect you will erase the testing results which is needed to pass the emissions test.

Well that may explain why the 5 monitors did not clear in over 724 miles and 20+ cold starts! Everytime I was told to disconnect cables from battery as told I was resetting mileage recorder to zero. I will be trying this 300-500 mile plan and see what happens. Thank you again!

[j cAT]

Originally Posted by gorent

Well that may explain why the 5 monitors did not clear in over 724 miles and 20+ cold starts! Everytime I was told to disconnect cables from battery as told I was resetting mileage recorder to zero. I will be trying this 300-500 mile plan and see what happens. Thank you again!

post back if the PCM is ready after the 300-500 miles. having a cheap code reader/reset tool is great to have. less than 100 USD you can check to see if you have any codes,see if the PCM is ready, and if necessary reset the computer codes so that you can trouble shoot the PCM system...

the more you spend the more these tools will test in greater detail and can be used on all vehicles OBD II..

[gorent]

Originally Posted by j cAT

post back if the PCM is ready after the 300-500 miles. having a cheap code reader/reset tool is great to have. less than 100 USD you can check to see if you have any codes,see if the PCM is ready, and if necessary reset the computer codes so that you can trouble shoot the PCM system...

the more you spend the more these tools will test in greater detail and can be used on all vehicles OBD II..

I do have a code reader and can clear codes, however I never get any fault codes that turn on "MIL" lights. I have been trying to get the ready monitors (5) to move from Not Ready to Ready. I have not had a fault code on over a year now. I hope this mileage thing works out. I will let you know how it does and at what mileage.