M119 CE Light 26
 

1994 E420.

Getting code 26 – upshift delay. But the car is running just fine. Theres no noticeable problem. Isn’t this switch, or relay or whatever down on the side of the tranny? Anyway to fiddle with it to see whats up?

WAIT WAIT WAIT....theres more!

Okay, maybe I am just retarded, but I totally forgot about something that’s actually a big deal. Under light acceleration, many times there is an RPM surge. Normally it'll jump from say 2000 to 3000 rpm. I haven’t paid enough attention to it to see if it’s happening during the 2nd to 3rd gear shift. I'll update later today after I drive a bit and let you know when that surge happens.

Could a faulty upshift valve (or whatever it’s called) be the cause of this?

The upshift delay valve delays the transmission from shifting from 2nd to 3rd gear when the car is cold. It allows the transmission to hold the rpm's higher for about a minute, or until you hit approx 45 mph.

Next time you start the car up in the morning, see if it is working.

If not, it usually caused by the upshift delay valve's inability to hold vacum.

The vacum hose leading to this valve could also either be blocked or cracked.