Mechanics

CODE READING

2000 Cadillac Seville • 135,000 miles

Why is it that my OBD system show codes the mechanic's scanner don't pick up? I took my 2000 Seville (140k mi) to two mechanics with codes that my OBD had stored (P0327 Knock sensor), but yet their scanner tool didn't pick up any codes.
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Thunder
December 13, 2011.




It is hard to say, there are unanswered variables. You are getting codes from the vehicles OBD feature, using info up, and on/off?

Factoryjack
Dec 13, 2011.
Yes, that's correct. As we speak, the mechanic is charging approx. $350 to do the job. Does that sound right (it's an SLS). Maybe, a small history, I read the code on friday morning before work NO chk engine light. That night I was coming home from friends house, I punched it to past a car, chk engine light came on. I drove with it on to see if it go off on it's own. It didn't. Monday morning I cleared the codes (only PCM P0327 current was detected by OBD). This morning driving to work (approx. 12mi), the code came back but NO ck engine light.

Tiny
Thunder
Dec 13, 2011.
The P0327 will not illuminate the check engine light, it will store it in failure records. That was the only code in the system? It is quite possible that you have other codes, type A, or B, that are turning the light on. These may set and clear intermittently, but will remain in failure records/freeze frame history data.

Factoryjack
Dec 13, 2011.
I've done some reading in the past mth on this site and other's about this code, you're the first person to talk about type A or B codes. What's the difference between the two? This morning, P0327 current was the only code. How do I clear memory? Disconnect the battery for an 1/2 hr?
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Tiny
Thunder
Dec 13, 2011.
If you are using the on-board functions, after it displays codes, it will give you the option to clear codes. Either by respective module, or all modules at once.

Diagnostic Trouble Code (DTC) Type Definitions

This information refers to domestic and export calibration packages. Use the DTCs that only apply to your specific RPO (regular production option). Each DTC is directly related to a diagnostic test. The DTC sets based upon the DTCs individual running and setting criteria.

The following are the types of DTCs and their code characteristics: Type A



Emissions related



Requests illumination of the MIL on the first trip with a fail



Stores a history DTC on the first trip with a fail



Stores a Freeze Frame on the first trip with a fail



Stores a Failure Record



Updates the Failure Record the first time the test fails each ignition cycle

Type B



Emissions related



The code is enabled after the first trip with a fail



The code is disabled if the second consecutive trip passes



Requests illumination of the MIL on the second consecutive trip with a fail



Stores a history DTC on the second consecutive trip with a fail



Stores a Freeze Frame on the second consecutive trip with a fail



Stores a Failure Record when the first test fails



Updates the Failure Record the first time the test fails each ignition cycle

Type C1



Non-emissions related



Requests illumination of the service lamp (not the MIL), or the service message on the first trip with a fail



Stores a history DTC on the first trip with a fail



Does not store a Freeze Frame



Stores a Failure Record when the test fails



Updates the Failure Record the first time the test fails each ignition cycle

Type C0



Non-emissions related



Does not request illumination of any lamps



Stores a history DTC on the first trip with a fail



Does not store a Freeze Frame



Stores a Failure Record when the test fails



Updates the Failure Record the first time the test fails each ignition cycle

Type X



Diagnostics that are coded in the software, but will not run for non-OBD?II export vehicles



Some domestic vehicles use DTCs



Even though codes are not stored, the DTC type table can still be used as a resource when diagnosing problems with systems that are associated with the type X DTCs

If a system is malfunctioning and the associated DTC has been disabled (type X), it may be beneficial to use the diagnostic table as a guide to aid in diagnosis. Many of the DTC tables include a functional check of the system that may pinpoint a problem. However, it is important to remember that the DTC tables are specifically designed for use only when a DTC is set. Therefore, a thorough understanding of the normal operation of the system being diagnosed is necessary and use of the tables for this purpose is at the discretion of the technician.

Factoryjack
Dec 13, 2011.

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