4.6L LH2 Engine with a DTC P0420 / P0430 Code - kw camshaft ECM P0138 P0158

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

Some 2004 XLR and SRX with LH2 engine may have a DTC P0420 or P0430 (converter efficiency code) set with a DTC P0138/P0158 (post O2 sensor code) set as well. If there is only a DTC P0420/P0430 code set, follow the diagnosis in SI.

If there is a code DTC P0138 and P0420 or a DTC P0158 and P0430 code set, replace the affected post O2 sensor first. Then drive and monitor that the associated converter efficiency diagnostic has run and passed. (See DTC P0420/P0430 code chart for test drive conditions). If the diagnostic runs and fails with the new post O2 sensor, then the catalytic converter should be replaced.

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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

(2004 Cadillac SRX, XLR with 4.6 LH2 engine)

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