What does it mean?
The control module keeps a timer that records how long the propulsion system has been switched off between two run cycles, usually called the engine-off or soak time. That figure matters because several self-tests only run after the vehicle has stood still long enough for temperatures to equalise, for example evaporative leak checks and the comparison of coolant and intake air temperature at start-up.
P02FF is stored when the module decides the stored inactive time is implausible: it comes back as zero, jumps to an impossible value, or contradicts what the temperature sensors and the other modules report. The fault therefore lies in the module memory, its permanent power supply or the shared time information on the network, not in a mechanical engine component. A very common trigger is anything that interrupts keep-alive power while the vehicle is parked.
Symptoms
- MIL on with the code stored, often after the vehicle has stood for a long period or after battery work
- Readiness monitors will not complete, so the vehicle cannot pass an emissions inspection
- Other codes appear alongside, especially evaporative system or cold start related entries
- Occasional loss of stored settings such as the clock, radio presets or learned idle values
- Slow cranking or other signs of a tired battery in some cases
- Engine performance itself usually feels completely normal
Likely causes
- Loss of keep-alive battery feed to the control module through a blown fuse, corroded connector or poor ground
- Weak or failing battery, or a battery that was disconnected or replaced during the last soak period
- Loose or corroded battery terminals causing voltage dips while the vehicle is parked
- Parasitic drain flattening the battery so the module loses its stored time value
- Network communication fault preventing the modules from agreeing on the time value
- Internal control module fault or corrupted memory
- Module calibration that the manufacturer has since updated
How to fix it
- Check the battery state of charge and carry out a load test before anything else
- Clean and tighten the battery terminals and the main ground straps, then repeat a voltage drop test on both
- Verify permanent battery voltage and ground at the control module connector with the ignition off
- Measure parasitic draw after all modules have gone to sleep and trace any circuit above specification
- Scan every module for communication faults and note any network codes stored with this one
- Confirm that the engine-off time shown in live data behaves sensibly after a genuine overnight soak
- Check for a manufacturer software update for the module before replacing it, since this fault is frequently corrected in calibration