A common issue with 2008 General Motors (GM) vehicles involves OBD2 resets and the crankshaft position sensor. After a battery disconnect or sensor replacement, certain readiness monitors, such as the EGR and Oxygen sensor monitors, might indicate “INC” (Incomplete) even after driving for an extended period. This article explores potential causes and solutions for this problem.
Aftermarket tuning can sometimes interfere with the readiness monitors setting correctly. Specific modifications to the vehicle’s computer system (PCM) might disrupt the expected parameters for emissions systems, preventing the monitors from completing their diagnostic cycles. Understanding which tables within the PCM’s tuning software control these functions is crucial for pinpointing the root cause.
Diagnostic scanners play a vital role in troubleshooting. Live data monitoring allows observation of critical parameters like long-term (LT) and short-term (ST) fuel trims, as well as oxygen sensor (O2) behavior. Ideally, fuel trims should hover around zero at idle and under light throttle, indicating proper fuel delivery. Rapid fluctuations in O2 sensor readings suggest they’re functioning correctly, but further analysis might be needed.
However, not all scanners display every parameter. Some might not explicitly show EGR function monitoring within the data stream. Accessing specific special test functions related to the EGR and Variable Valve Timing (VVT) systems can reveal whether the PCM is attempting to run these tests. An “INC” status often persists despite significant mileage, suggesting a problem beyond normal driving cycles.
While some tuners claim they can manually set readiness monitors to “Ready” regardless of actual functionality, this is not a recommended solution. It bypasses the diagnostic process and might mask underlying issues. Addressing the root cause, whether it’s a faulty sensor, wiring problem, or tuning conflict, is essential for ensuring proper vehicle operation and passing emissions tests. Even with one incomplete monitor, passing an emissions test might be possible, but resolving all “INC” statuses is crucial for long-term reliability and performance.
