Transmission Upshift Delay
WARNING: This page is about a different car, the 1992 Mercedes-Benz 400E. However, it is still accessible from the selected car via links, so may be relevant.
To help the catalyst to reach it's operating temperature faster, the no-load and partial-load 2-3 upshifts are delayed a maximum of 15 seconds after engine start-up when coolant temperature is 32-122°F (0-50°C), causing upshift to occur at a higher engine RPM. The LH control unit delays upshift by controlling upshift delay switchover valve. See Figure for location.