No "reverse", then "service engine soon"

[markm]

Tried to leave for work this morning. Started my truch as usual, shifted to reverse to back out of the garage and the truck would did not move. Back to Park and then to Reverse again, now the R is flashing. Turned the key off, waited a few minutes and started up again. This time reverse works, but now have the "service engine soon" lit up. Going back to dealer Monday. Have 30K miles, tranny fluid and filter changed by dealer at 25K. Any thoughts?

[mtomac]

check the rubber acordian boot on the shift linkage at the tranny to make sure it isn't sticking or holding up. Otherwise it's probably the NBSU switch.

[heartbeatcanada]

Ditto to what Mike said, NSBU switch. Later

[Modified]

If you just had your tranny fluid changed 5K ago, Mike L may be on to something. Even some Dealers don't know how to properly check level AFTER the fluid is up to temp.
You wouldn't happen to have a Deep Ally Pan, would you? If so, you may have been filled three quarts short.

[markm]

Thanks for the input. Will check the shift linkage boot. Transmission fluid is at the right level.

[Jimamatic]

Markm,
Mine did the exact same thing the other day.
Taking it to the dealer tomorrow. It's a 2001
2500 hd d/a with the old style NSBU switch.
The wierd thing is that according to the owners
manual,the check engine soon light is supposedly
tied to environmental and emmisions systems. The
book also said that it could be as simple as the fuel cap not being on right. So I took the cap
off, put it back on and taaa daaa.. the light
went out. Still taking it to the dealer to check
for codes. What I want is a new NSBU switch..

[markm]

Update on "no reverse and service engine soon":

The incident happened on a Wednesday and did not drive the truck again until Monday AM to take to the dealer. Started the truck as usual, shifted into reverse, no problem and "service engine soon"
light went out.

Dealer put computer on it and could not find any problem code stored. Test drove and everything checked out.

[Jimamatic]

Update.
Took my truck to the dealer. They were able to
trace the problem to a faulty reverse pressure
switch signal. The fix was to reprogram the
transmission control calibration to correct
the incorrect signals. It sounds to me they just
reflashed the TCM. Sounds good to me I guess.
As long as it fixed the problem.