Navigating OBD2 system issues can be frustrating, especially when you’re facing problems with your 2014 Chevy Impala’s readiness monitors. Let’s delve into understanding these monitors and what might be causing them to show as “not ready” (INC – Incomplete) on your scanner, even after driving a significant distance.
One common area of concern, as raised in discussions among car enthusiasts, points to aftermarket engine tuning. If you’ve had your Impala tuned for performance enhancements, this could potentially be the root cause of your readiness monitor issues. While tuners aim to optimize your vehicle’s performance, sometimes these modifications can inadvertently affect the parameters that the OBD2 system uses to set readiness monitors.
For instance, let’s consider fuel trims. Your scanner readings are showing that both long-term fuel trims (LTFT) and short-term fuel trims (STFT) are consistently at 0, even when idling or slightly accelerating. This is unusual and could indicate a problem. Healthy fuel trims should fluctuate as the engine management system constantly adjusts the fuel mixture to maintain optimal combustion. Stuck-at-zero fuel trims could be a symptom of a tuning issue or a sensor malfunction preventing proper feedback to the engine control unit (ECU).
Similarly, the behavior of your oxygen sensors (O2 sensors) is crucial for readiness monitors. You mentioned that your O2 sensors are fluctuating up and down quickly, which is generally a good sign, indicating they are active and responding to changes in exhaust gases. However, if the readiness monitors related to O2 sensors are still incomplete, there might be a more subtle issue at play, or the problem might lie with another monitor blocking the O2 sensor monitor from completing.
Interestingly, you noted the absence of explicit EGR (Exhaust Gas Recirculation) function monitoring in your scanner’s data stream tab. While some parameters might indirectly relate to EGR function, the lack of a direct EGR monitor reading could be noteworthy. In the “Special Tests” section under “IM” (Inspection/Maintenance), you observed EGR/VVT (Variable Valve Timing) listed as readiness monitor functions, showing “INC” in your case, which hasn’t cleared despite extensive driving. This persistent “INC” status for EGR, even on a car equipped with EGR, strongly suggests a potential problem preventing this monitor from setting.
The tuner’s suggestion to “set it to ready” even without a functional EGR monitor (though your car has EGR) highlights a workaround, not a true fix. While this might resolve your immediate emission testing hurdle, it doesn’t address the underlying reason why the EGR monitor isn’t setting naturally. Ideally, all readiness monitors should set correctly without forced settings.
Regarding the Throttle Position Sensor (TPS), you mentioned it being displayed in percentage (%) rather than voltage (V). While percentage-based readings are common, and the inability to change the value display isn’t necessarily an issue, ensuring the TPS is functioning correctly is important for overall engine operation and potentially for some readiness monitors.
You’ve updated your scan tool software (9680), which is always a good step to ensure you have the latest features and bug fixes. However, the core issue with the readiness monitors seems to persist.
With only about 150 miles driven after a battery disconnect, it’s still within the timeframe for some monitors to reset. However, your suspicion that the EGR monitor might never clear based on past experience seems valid, especially given the tuner’s comment and the persistent “INC” status.
Passing an emission test with one “not ready” monitor is sometimes permissible depending on local regulations. However, resolving the underlying issue causing the readiness monitor problems is always the best approach for optimal vehicle performance and long-term reliability.
Moving forward, communicating these observations, particularly the fuel trim readings, the EGR monitor status, and the tuner’s approach, with your tuner is crucial. They should be able to investigate whether their tuning adjustments are indeed affecting the readiness monitors and potentially revise the tune to allow all monitors to set correctly. Further diagnostic steps might also be needed to rule out any sensor malfunctions or other mechanical issues impacting the OBD2 system’s ability to complete its self-tests.
