Drive Engine Run-Up Test (DERU)

CAUTION: Do not conduct this test for over 30 seconds, or without periodic driving or shifting to neutral to circulate transmission lubricant; otherwise the transmission will overheat causing severe damage to the automatic transmission.

1. If the vehicle has an automatic transmission, a Drive Engine Run-up Test (DERU) can be conducted. Both the parking brake and service brake should be set, and care should be taken to perform the test with enough space ahead of the vehicle to eliminate the possibility of an accident should the vehicle unintentionally lurch forward.

2. Put the transmission in Drive and run the engine up and down between idle and approximately 2000 rpm and note the nature of any vibrations and noises and the rpm. This test is particularly good for exciting the exhaust system, and hanging keys on the tailpipe to serve as a "telltale" is useful.