Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1.18 In-use monitor performance ratio - kernel function: Notes
The in-use monitor performance (IUMPR) kernel function represents the core of the software algorithms in the OBD II system implemented to individually track and report in-use monitor performance, in the standardized tracking and reporting format, for every monitor of the following components/systems (subsystems A...E):
- A: catalyst
- B: front oxygen sensor
- C: evaporative system (only 0.02 inch leak detection)
- D: VVT system and
- E: secondary air system.
All monitors for which an in-use performance record is required do have an interface (a function identifier) through which they communicate with the IUMPR kernel function. It is this kernel function that does the actual tracking and preparation for reporting in the standardized format. See Fig 1 below. The IUMPR kernel function additionally tracks and records the ignition cycle counter, the general denominator for every driving cycle and determines the monitor with the lowest numerical ratio within each group that has multiple monitors.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.