2014 Mercedes-Benz CLA250: Check Engine Light Reset Attempt
December 04, 2013
A couple of days ago the Check Engine light winked on while another staffer was piloting our near-new 2014 Mercedes-Benz CLA 250. However, as is often the case, he couldn't correlate its arrival to anything special he was doing at the time. It did not come on during the startup sequence or while climbing a steep grade. He was just, you know, driving.
For its part, the car is fine. No hiccups, no reluctant acceleration, just the dang light on the dash. Well, maybe the fuel economy is a little underwhelming, but it's hard to be sure that's a thing with just 476 total miles on the clock.
I have a couple of low-cost OBD code scanners at home, so I hooked each of them up to see what they could tell me.
The first was the Scan Gauge II. It came back with a single diagnostic trouble code with an ominous-sounding title: P0004 - Fuel Volume Regulator Control Circuit High.
Farther on in the definition, though, it points out that this code is "not common and sometimes is shown in error due to the design of the code reader." It goes on to say the first thing I should do is attempt to re-read the code with a higher-quality code reader.
Our CarMD is a fancier device, and it came back with a fancier code: P24D6. But this one is not defined on the common DTC-code websites except to say that it's an automaker-specific code. In other words, it's not one of the required OBD-II codes and I can't decode it without Mercedes equipment.
So I went back to the advice page for P0004: reset the Check Engine light and see if it comes back. That worked for the entire weekend, some 250 miles of unhurried driving, a typical mix of city and freeway errand-running and holiday shopping. "Must have been a fluke," I thought.
But then I started the engine in order to read the odometer mileage in preparation for writing this status update. Of course the light chose that moment to wink back on.
Enough messing around with toys. It's time for a dealer visit.
We're not the only ones. I've since learned that Mercedes CLA forums began lighting up in October with complaints from others about the P24D6 fault code. Like our car, their DTCs appeared in the first few hundred miles.
At first there was no remedy for what has been described as an OBD software glitch, but that changed in early November. Thing is, that's about the same time we took delivery of our car. We must have missed the fix by days, maybe hours.
We'll keep you posted once we schedule an appointment and bring it in. But at least it doesn't sound like a big deal, except for the hassle.
Dan Edmunds, Director of Vehicle Testing @ 715 miles