How do I reset the check engine light after fixing problem. Code read glow plugs and they have been replaced but light still comes on. 1999 Mercedes E-300 diesel. Thanks
Many auto parts stores have a code reader you can borrow to read out the codes and reset the light. If the light comes back on, then you have a new problem, or the repair did not fix the original problem.
Maybe the code you got (?) does not mean the glow plugs are bad and the problem is in the glow plug circuitry instead.
It’s easy enough to test glow plugs and verify whether any of them are really bad or not.
I checked the resistance at relay and #'s 1, 3 and 5 were way out of range. Due to labor involved I replaced all at same time with OEM’s.
I believe the light should go out after a few drive cycles. If no, it may not have been the glowplugs that were causing the light.
Like Joseph mentioned, if the problem has been fixed a few drive cycles will put the light out.
I like playing around with things to see how they work.
I was curious how many drive cycles it would take to kill the check engine light on my wifes 02 Sonata.
I lossened the gas cap & drove until the CEL came on. Retightened the cap & the magic number was 9 drive cycles over 2 days.
Drive cycle equals start it,drive til it’s warmed up, shut it off.
On most cars of that vintage you can reset the light by disconnecting the battery for a minute or two. On Benz’s, be careful you have the radio code to restore it’s operation if so equipped before disconnecting the battery…