These instructions apply to the Fiat 500 (312) 2007-present.
For other models, please choose your vehicle here.
The Fiat 500 (312, 2007–Present) hides an owner-accessible cluster self-test behind the trip button. It is the same hardware test a workshop uses to check the dials, warning lamps and amber LCD, and you can trigger it yourself in your driveway with nothing more than the ignition key — no diagnostic tool, no code reader.
What the hidden self-test is and what it shows
The 500’s Magneti Marelli cluster has a built-in self-test routine that the speedometer and rev-counter pointers, all the warning lamps and the central amber display run through in sequence. It is meant for the assembly line and the dealer, but the button combination that starts it is not locked, so any owner can use it. Running it tells you, at a glance, whether a problem you are chasing is in the cluster itself or somewhere upstream.
During the test you will normally see:
- Gauge sweep — the speedometer and tachometer needles drive fully clockwise and then back to zero. A needle that sticks, lags or stops short points to a tired gauge motor inside the cluster.
- Warning-lamp test — the indicator and warning LEDs light in turn. A lamp that never comes on here is a dead segment, not a fault elsewhere in the car.
- LCD segment test — the amber central display fills its pixels and cycles its segments so you can spot missing rows, a half-blank odometer or a pixelated trip readout (a very common 312 fault).
Treat this as a quick health check of the cluster display, not a fault-code reader. The 500 stores its actual trouble codes in the body and engine modules, which need a scan tool to read.
How to open the self-test
- Park, apply the handbrake and make sure the car is switched off with the key out (or, on keyless cars, the dash dark).
- Find the small trip / reset button on the instrument cluster (the one you normally press to swap Trip A/Trip B and to zero the trip meter).
- Press and hold that button down.
- While still holding it, turn the ignition key to MAR (position II — dash live, engine not cranked). On Start/Stop cars, press Start once without touching the brake so the ignition comes on but the engine does not fire.
- Keep holding until the needles begin to sweep and the warning lamps cycle, then release. The self-test now runs.
If nothing happens, you almost certainly cranked the engine or let go of the button too early. Switch off and try again, holding the button down before you reach MAR.
Reading the result
Watch one element at a time. Both needles should sweep smoothly to the stop and return cleanly to rest; every warning symbol should illuminate at least once; the amber display should show full, solid segments with no missing blocks or dropouts. If the dials and lamps all pass but a warning light is still on during normal driving, the cluster is fine and the fault is in the system that lamp represents — that is your cue to read the stored codes. If a needle or display block fails the test, the cluster is the culprit and needs repair or replacement.
How to exit
Simply turn the ignition off (key to STOP / position 0, or press Start to shut the dash down). The self-test ends immediately and the cluster returns to normal at the next key-on. The routine changes nothing and stores nothing, so you can repeat it as often as you like.
Frequently Asked Questions
Does this work on every Fiat 500 (312)? The trip-button self-test is present across the 312 range — petrol, TwinAir, diesel and the Abarth versions — because they share the same Magneti Marelli cluster family. Very early low-line clusters show fewer LCD elements, but the gauge and lamp test still runs.
Will it show me my fault codes? No. It is a hardware self-test of the dials, lamps and display only. To read engine or ABS trouble codes on a 500 you need an OBD-II scan tool plugged into the port under the dash.
The trip display on my 500 is pixelated — can the test confirm the cluster is at fault? Yes, and that is one of its best uses. If the LCD segment test shows missing or scrambled pixels, the known 312 display fault is confirmed and the cluster (or its display ribbon) is what needs attention, not the wiring.
Can running the self-test reset my mileage or change a setting? No. It only exercises the existing hardware; it does not write to the odometer or alter any setting.
My needles don’t sweep at all when I try it — bad cluster? Not necessarily. First confirm you held the trip button down before turning to MAR and that the engine did not start. If the combination is right and the needles still refuse to move, then a failed gauge motor or a dead cluster is the likely cause.
If a warning lamp passes the cluster self-test but keeps coming back on, the next step is to read the actual diagnostic trouble code behind it — you can look up what any Fiat code means at autodtcs.com.
Independent guide — not affiliated with Fiat. Always follow your official service manual and safety precautions. Read our full disclaimer.