P05F8 code meaning
Reductant Heater Control Module Performance
Powertrain system Generic code P05xx codes Check engine light
What P05F8 means
P05F8 is the function check of the DEF heater control module: its feedback does not match the command – heating current or power, temperature rise, or an internal module fault. The code is documented for Chrysler's 3.0 L EcoDiesel in the 2014 Ram 1500 and Jeep Grand Cherokee: several bulletins list it together with the heater codes P20BA, P20BE and P20C2, and the fix in each case was only reprogramming the engine module – a diagnostic that was too sensitive rather than a hardware defect. It is not on Chrysler's inducement list. Ford checks the same function under heater plausibility codes. Thresholds for P05F8 are not published. If it returns after a software update, check the heater elements in tank and lines and the module supply (P05ED).
P05F8 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P05F8
- Check engine light on
- Usually no driveability issue
- DEF warning in cold weather, possible heater codes P20BA/P20BE/P20C2
Common causes of P05F8
- Most likelyEngine module software (Chrysler 3.0 L 2014: diagnostic revised by reflash)
- PossibleHeater control module faulty internally
- PossibleHeater element or line in tank or hose with abnormal current
- Less likelyUnstable module supply or ground
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant heater control moduleReductant heatersEngine control module
What each part of P05F8 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| F8 | The exact fault in that area. |
What to do next
- Note P05F8 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P05F8
What does P05F8 mean?
P05F8 means "Reductant Heater Control Module Performance". P05F8 is the function check of the DEF heater control module: its feedback does not match the command – heating current or power, temperature rise, or an internal module fault. It is a generic code, so it means the same on every make.
Is it safe to drive with P05F8?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P05F8 fail an emissions test?
Yes, it can. P05F8 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P05F8 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P05F8 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.