history codes important?
Thread Starter
Instructor
Joined: Jan 2017
Posts: 169
Likes: 22
From: Shelton WA
history codes important?
Hi all-well, finally at a point where we are going to begin the process of getting into a C5. Have finally recovered a bit financially after having to sell our 65 mustang vert show car (gotta love property disputes) to make it happen in the next few months. anyways, after TONS of reading on this awesome forum, we went to drive a 99 vert just for fun (it was on a lot, so i didn't feel too bad about wasting their time since we had no intentions of buying it. just mainly really wanted to see if we would like the Pewter color and compare it to silver-grey enough here in the PNW 8 months out of the year!). So got a great chance to test my memory in checking the DIC codes. Had a few come up such as some SDM codes (air bag com i think?), some LDCM and RDCM codes (l and r door), and some RFH codes (not sure on these). so, these were all history codes. so, just thinking ahead when we actually do find one we are ready to move on, are any of the history codes a total red flag and a sign to run? not talking about these specifically, but any of them-i want to check out as many C5's as we can so i know what i'm doing (or at least look like i know what i'm doing!) when the right one comes along-thanks all!
jp
jp
Safety Car
Joined: Apr 2007
Posts: 3,640
Likes: 83
From: . New York
Nope. None of that matters (really).
Almost without fail, codes are thrown due to voltage fluctuations on starting and run up.
Clear the codes and drive......the ones that then come up are current, ya.....those you have to think about, but Hx codes......they are......history
Almost without fail, codes are thrown due to voltage fluctuations on starting and run up.
Clear the codes and drive......the ones that then come up are current, ya.....those you have to think about, but Hx codes......they are......history
Thread Starter
Instructor
Joined: Jan 2017
Posts: 169
Likes: 22
From: Shelton WA
Awesome-exactly what i needed to know. Thanks so much! (different world than the vintage stangs with all the tech in the vettes....both good and bad i guess. good in the fact you know something may be up...bad in the fact you know something may be up!...in the mustangs, mostly you never knew something wasn't quite right until they either pee'd themselves or just stopped running-usually right in the middle of a parade 
) Thanks again for the reply-
jp
) Thanks again for the reply-jp
Melting Slicks
Joined: Aug 2011
Posts: 2,423
Likes: 200
From: Atlanta GA
Hi all-well, finally at a point where we are going to begin the process of getting into a C5. Have finally recovered a bit financially after having to sell our 65 mustang vert show car (gotta love property disputes) to make it happen in the next few months. anyways, after TONS of reading on this awesome forum, we went to drive a 99 vert just for fun (it was on a lot, so i didn't feel too bad about wasting their time since we had no intentions of buying it. just mainly really wanted to see if we would like the Pewter color and compare it to silver-grey enough here in the PNW 8 months out of the year!). So got a great chance to test my memory in checking the DIC codes. Had a few come up such as some SDM codes (air bag com i think?), some LDCM and RDCM codes (l and r door), and some RFH codes (not sure on these). so, these were all history codes. so, just thinking ahead when we actually do find one we are ready to move on, are any of the history codes a total red flag and a sign to run? not talking about these specifically, but any of them-i want to check out as many C5's as we can so i know what i'm doing (or at least look like i know what i'm doing!) when the right one comes along-thanks all!
jp
jp
A sensor or actuator could be on its last legs and thus is working intermittently. Could also indicate a detonation issue was experienced and that could be troubling, especially if it happens intermittently.
I would catalog and save the historical codes by category and actual system effected, including the meaning of the code. Here is one place you can do a lookup of the codes and the system(s) affected.
http://computer-logic.us/Obd2Lookup.
You can enter a list of codes, separating each one by a comma.
Clear the codes after cataloging them and see if they pop up again in the near future. If not, you are probably OK. If they reoccur say within a few days or weeks of each other, could indicate an impending issue.
Last edited by bikeriderga; Jun 4, 2017 at 12:21 PM.
Drifting
Joined: Mar 2013
Posts: 1,496
Likes: 353
From: Little Rock Arkansas
You shouldn't completely disregard any stored H codes. Many of the codes will possibly point to a problem but often the problem is not of far enough detriment to require a check engine light illumination, hence the need to know what codes are stored and what they are for.
A note; it is very difficult to find a used C5 that does not have some sort of code stored, especially pre-2001 cars. When you start the car, the BCM and PCM run their checks and there are often minor communications errors. These usually pop up as small anomalies, such as receiving the "pull key" message, and then are stored. These sort of stored anomalies shouldn't throw up a serious red flag but any codes stored that relate to sensors that affect driveability should be checked out. Often checking grounds and wiring helps many communication errors a C5 will have.
Many C5 owners go through a lot of headaches to eliminate all stored DIC codes; it's a product of ownership.
A note; it is very difficult to find a used C5 that does not have some sort of code stored, especially pre-2001 cars. When you start the car, the BCM and PCM run their checks and there are often minor communications errors. These usually pop up as small anomalies, such as receiving the "pull key" message, and then are stored. These sort of stored anomalies shouldn't throw up a serious red flag but any codes stored that relate to sensors that affect driveability should be checked out. Often checking grounds and wiring helps many communication errors a C5 will have.
Many C5 owners go through a lot of headaches to eliminate all stored DIC codes; it's a product of ownership.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Velocity_Vette & 8VETTE7 are absolutely correct! 
All DTCs are important and are triggered for a reason. Like 8VETTE7 stated, clear the DTCs and BEFORE you turn the engine off, read what is stored.
Yes, H codes for the most part are not as critical as C DTCs but, a new C5 that is working properly rarely has any DTCs at all.
Something just isn't quite right. Could very well be a weak battery or a glitch in light off communications.
All DTCs are important and are triggered for a reason. Like 8VETTE7 stated, clear the DTCs and BEFORE you turn the engine off, read what is stored.
Yes, H codes for the most part are not as critical as C DTCs but, a new C5 that is working properly rarely has any DTCs at all.
Something just isn't quite right. Could very well be a weak battery or a glitch in light off communications.
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Pro
Joined: Oct 2013
Posts: 506
Likes: 54
From: Tulsa OK
I totally disagree.
Most but not all of the sensors that produce codes do so when the engine is running and at the time the code is generated it shows as C or in some cases HC. When the engine is turned OFF the codes that were C get converted to H since they can no longer be C if the engine is not running. So pulling codes with the engine OFF will report most codes as H.
It is possible to pull codes with the engine running. So if a sensor has produced a code during the current ignition cycle then the code will show as C or HC. Further H codes are an audit trail of events that have happened and can be VERY useful in identifying problems.
I do agree that codes are produced for many reasons and voltage fluctuations is one of those. I also agree that you should clear the codes with the engine off then start the car and drive it for a nice (long if possible) drive . When you return pull the codes BEFORE you shut off the ignition. Codes that have occurred are the ones that you need to be concerned about. EVEN if they show as an H.
To pull codes with the engine OFF you need to use the RESET button to clear any messages from the DIC and then pull the codes as normal.
Most but not all of the sensors that produce codes do so when the engine is running and at the time the code is generated it shows as C or in some cases HC. When the engine is turned OFF the codes that were C get converted to H since they can no longer be C if the engine is not running. So pulling codes with the engine OFF will report most codes as H.
It is possible to pull codes with the engine running. So if a sensor has produced a code during the current ignition cycle then the code will show as C or HC. Further H codes are an audit trail of events that have happened and can be VERY useful in identifying problems.
I do agree that codes are produced for many reasons and voltage fluctuations is one of those. I also agree that you should clear the codes with the engine off then start the car and drive it for a nice (long if possible) drive . When you return pull the codes BEFORE you shut off the ignition. Codes that have occurred are the ones that you need to be concerned about. EVEN if they show as an H.
To pull codes with the engine OFF you need to use the RESET button to clear any messages from the DIC and then pull the codes as normal.
Thread Starter
Instructor
Joined: Jan 2017
Posts: 169
Likes: 22
From: Shelton WA
Wow-just want to say thanks for all the info. DEFINITELY very helpful! (i feel kinda bad as i don't own a C5 yet, so i'm just kind of sponging advice, but ive learned its better to go into a different car with as much info as you can have!) And i'm glad my old 65 mustang vert didn't have all this....would have taken a super-computer to store all the thrown codes 