Check engine light blinked a few times twice but nothing reported and nothing in the diagnostic file

Cat 3126E Allison 6 speed in a 2003 Fleetwood Discovery. Yesterday, while rolling hills in NY, my check engine light came on and went into a 10 second blink for 30 seconds. Did this twice. All readings on my monitor were good. Checked the diagnostics file and there was nothing in it.

I'm new to VMSpc and diesels for that matter. Is there a reason that the light would come on and VMSpc not capture a code? Is there a way to use VMSpc to get the code from the ECU? Is there another way to get a code from the ECU?


Check engine light

Called Freightliner. They said it was almost certainly low coolant level in the overflow tank. The sensor is in the back of the tank and when rolling hills, if the coolant is low in the tank, it can slosh enough to uncover the sensor which will show the check engine light but NOT trigger a diagnostic message. He said that was about the only thing it could be and, indeed, the level was about an inch low. Added about 1/2 gal of coolant and am confident the problem won't repeat.

pulling codes from engine computer


To answer your second question, yes you can access the memory in the engine computer with Cat ET software and read all codes. The software will also change many of the standards that have been programed into the engine computer. Also wipe all codes. I do not recommend most people access the engine, transmission, or ABS computers this way unless you have read the programming manuals and understand them.
Most coaches will also let you read codes from the engine through the cruise control. Some will clear when read and others will require Cat ET to clear the codes. Allison generally will let you read codes through the shifter console. You can also load 330 HP firmware into the computer for the 3126 engines that are set up with less HP. This gets a little complicated depending on the year and serial number of the engine. and Cat ET is necessary along with the correct firmware update file from Cat.
Love electronics, don't you?

BTW, I am built on a 2001 freightliner frame. My light bar has a low water light and a buzzer when the coolant light comes on. Does not use the check engine light. Just came back from a 2K trip and during the last 1K used up 2 gallons of coolant, have (for the last 2 years) used about 1/2 gallon each year and could not find the reason. Ha, it was a bad coolant tank leaking. The local dealer had it in stock on the shelf and told the wife they use enough of them to keep it in stock. Also that this tank is only used on pushers.

That's interesting. I've read

That's interesting. I've read about pulling engine codes through cruise control but had forgotten about it. I was counting on VMSpc to give me that information for my C-10 and ended up paying a local mechanic to pull the codes for me. I discovered a) low coolant (Duh!) and bad crank and cam sensors. I filled up the tank and changed those sensors and it made a huge improvement.