i recently purchased a very clean 1994 Cheverolet Suburban w/ 6.5litre Turbo Diesel.
the previous owner had replaced the engine at 139500 miles because of cracked heads,- this new motor is supposed to have less then 50,000 miles on it.-( i have paperwork for engine replacement cost of 2500.00 and 2000.00 for the install )

there is just over 500 miles on the engine since the replacement- but i do have a symptom -

service engine light comes on when i get on the highway and get to about 65mph- also it seems to not have as much power as it should when climbing hills- basically you hit a wall with the power even though you still have some gas to give. even when you floor it - it doesn't seem to have all the get up and go it should.- in regular city driving conditions you do not notice anything irregular- the engine seems to run strong and solid- it only seems to happen when i get on the highway at higher speeds. service engine light does not re-appear after the vehicle has been re-started but will come on consistently at higher speeds over approx. 60mph

***Update: - just ran the paperclip jumper diagnostic- as seen here:
http://dieselplace.com/forum/showthread.php?t=16399
starts out with 1/111 (13)? - but i thought it was supposed to be 1/11 (12) 3 times to show diagnostics was working?? well any way next code is 1111111/11111111 (78) : Turbo Wastegate Solenoid Fault- then it goes back to 1/111 and repeats...

thanks for any ideas or help.

regards
[email]briank@seattledsp.com[/email

use the paper clip type code reader as listed in the faq's. or go to any number of shops that'll read codes for free. auto zone comes to mind. once you know the codes post them here.

just ran the paperclip jumper diagnostic- as seen here:
http://dieselplace.com/forum/showthread.php?t=16399
starts out with 1/111 (13)? - but i thought it was supposed start with 1/11 (12) -3 times to show diagnostics was working?? well any way next code is 1111111/11111111 (78) : Turbo Wastegate Solenoid Fault- then it goes back to 1/111 and repeats... never does a code 12: 1/11

DTC 13 Engine shutoff solenoid circuit fault

FOR DTC 78, check for vacuum at idle, ~25" at the solenoid and ~15" at the wastegate.

thanks for the replies- not sure i have the tools or the knowhow to do much more . - what is the typical repair scenario for these faults on this motor? cost?
how easy to repair?
i have chilton manual but it seems limited.....

thanks

Brian I had some problem ended up being the wastgate solnoid cost me 30 bucks at dealer and took 1 min to change out also check your vac hoses for cracks the solnoid is on drivers side valve cover

texan ron- thanks for the info- i'll look into it- can anyone direct me to a diagram that shows the wastegate solenoid? if it's a simple fix i'll do it myself- just need to know what i'm looking for.

thanks

Diesel Engine Wiring, RH Sidehttp://www.alldatadiy.com/alldata/AFI~V5666790~C21449~R0~OB0~P4R0H~N/0/41746505/42420131/42420134/42420238/34853741/34869954/34849301/113972816/113973065/62534223

That picture should be in FAQ.

texan ron- just to let you know- everytime you refresh this page the picture changes???

thanks again for the info though

I've been experiencing the same thing with my '94 6.5TD, along with a slight oil leak that I finally tracked down the source of.

Symptoms are SES light at highway speeds (although this went away all winter long here in Buffalo, NY) and about 2 0z of oil that drips slowly from underneath the turbo after the engine is warm. Paperclip test reveals only code 78.

Last weekend I washed that whole side of the engine compartment, since it was so covered in oil and grime I couldn't see where the leak was coming from. I then drove it back and forth to work one day last week (I usually drive my car in the summer) and checked where the leak was coming from.

Lo and behold the oil seems to be coming from the middle of the turbo, where the two sections jion together. I don't know whether there is a gasket or something in there that is replaceable, or how to approach that problem. I'm guessing I also need a new wastegate solenoid to fix the code 78, right?