Here is some info:LM7, L59 or L33 Engines with Cold Start Rough or Incorrect Idle, Misfire, Malfunction Indicator Lamp (MIL) or Flashing Requiring O2 Sensor Replacement (Reprogram PCM)
Models: 2004-2005 Cadillac Escalade
2004-2005 Chevrolet Avalanche, Silverado 1500, Suburban, Tahoe
2005 Chevrolet Silverado Hybrid (HP2)
2004-2005 GMC Sierra 1500, Yukon, Yukon XL
2005 GMC Sierra Hybrid (PH2)
with Vortec 5300 5.3L V-8 Engine (VINs T, Z, B -- RPOs LM7, L59, L33)
Some customers may comment on a Malfunction Indicator Lamp (MIL) On or that the MIL is flashing. An actual engine misfire may or may not be felt along with an incorrect idle speed. Typically this occurs during cold winter months, on cold engine starts. Some vehicles may have been previously serviced for the same condition. Technicians may also find the following DTCs stored with the Tech 2 P0131, P0133, P0134, P0137, P0138, P0140, P0151, P0153, P0154, P0157, P1133, which may be in conjunction with P0171, P0174, P0300 and P1138.
Water shock occurs when water droplets are present in the exhaust. The water in the exhaust contacts the sensor element inside the HO2 sensor, causing the HO2 sensor element to crack.
Upon diagnostic investigation, the technician may find that the HO2 sensor requires replacement. In addition to replacing the affected HO2 sensor, these vehicles should also be reflashed with the latest PCM calibration. Important: If a DTC P0420 or P0430 is stored along with DTC(s) P0300, the catalytic converter diagnostics in Service Information (SI) must be followed to determine if the catalytic converters are operating properly.
There is a good chance the cat converters got damaged from the missfire. Post back with any other questions and what you find.
Monday, January 5th, 2009 AT 3:34 PM