Q What does the check engine light mean on the dashboard?
I have a 2017 Euro 6 Fiat Ducato motorhome and have recently noticed the amber ‘Check Engine’ warning light is on. I am not having any problems, though.
Using a scanner, the fault code comes up as P1581 15, which my research shows is due to a short-circuit fault in the crankcase bypass oil heater (necessary when travelling in very cold conditions).
However, neither our diesel mechanics nor our service agent can find or resolve the problem.
Can I disconnect the heater? Can I get rid of the warning light? If I ignore it, what happens if I get another engine fault?
Dave Monks A I am not as familiar with the Euro 6 Fiat Ducatos, but I suspect that your motorhome does not have a crankcase bypass oil heater. But we can circle back to that one later.
The ‘Check Engine’ warning message is a generic alert that something peculiar is amiss. I have seen it with alleged glow plug faults, alleged oil pressure warnings, air-con gas pressure faults and many, many more.
In almost all cases, it has been an indication that there is something wrong with the wiring and, in your case, there may well be a short between almost anything and a cable that would be connected to the device that you mentioned, if you had one, and because it has become live or has earthed, it has upset the engine computer. That is why I referred to the faults above as ‘alleged’ because, in reality, it is almost never the device described by the diagnostic unit that is at fault. Diagnostics are, by their nature, a means of finding clues, not definitive answers.
The most likely area for this fault would be somewhere in the main engine loom that connects to the left-hand side of the ECU or in the bundle of wiring that runs under the nearside headlamp from under the fusebox and heads off into the cab. Finding the problem requires unpicking the tape that binds the wires together and checking each and every cable. It is a slow process. I would definitely start by attacking the bundle under the headlamp. Almost all of the time, the issue it is in there.
As regards the option of ignoring it... You are almost certainly doing no harm but you are correct in that you may not be alerted to another warning that may be more critical. So, get this looked at sooner rather than later.
Nick Fisher