G2: FAQ: Error Codes: CEL 12

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Code 12 is one of the most commonly seen CEL error codes on Legends. It is set when the EGR valve does not properly respond to the open and close requests as they are sent by the ECU. Cleaning the EGR pipes and passages will not fix this problem or clear the code. The Legend is not equipped with an EGR flow sensor, so the ECU has no way of knowing if/when the system is clogged. It only knows if the valve opens when it's supposed to, and closes when it's supposed to. To properly diagnose the issue however, the EGR system must be clean and free-flowing, so you'll want to clean it all anyway. It is also an essential system for the proper and safe operation of the engine (read more on that here). If you're unsure of when the EGR was last cleaned, it's practically a sure thing that yours is clogged and completely blocked up. It is not enough to simply remove and clean the EGR pipe between the passenger side head and intake manifold. You must also remove the intake manifold and open it up to clean out the lower section. There is a DIY guide for the cleaning procedure of the EGR system here. Once the EGR system and intake manifold are clean, continue with the following flowchart.

To ensure your CEL code is current and not an old code for a problem that has already been resolved, you'll first want to reset the ECU to clear all stored codes. If you have done this recently or you are sure that your code 12 is new, you can skip this step. To reset the ECU, with the engine off and key removed from the ignition, remove the #15 fuse labeled ACG(S) in the under-dash fuse box for about 10 seconds and then replace it (See step 4 of the following guide for more details on resetting the ECU: G2: DIY: Diagnosis: Pulling Codes). Drive the car after resetting the ECU. If CEL code 12 returns, continue with the following flowchart.

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Figure B
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(Fig. B) With the engine fully warmed up and at idle, disconnect the #11 vacuum hose from the EGR valve and connect it to a vacuum pump/gauge. Does the gauge indicate any vacuum?

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