steelydan
03-23-2005, 11:30 PM
While driving home tonight SES came on. Code 33 and 78.
Last time I had 33 the Baro sensor's plug had come loose and I have since tie wrapped it.
-checked all vacuum lines to solenoids. Vacuum pump is 3 months old and I replaced vacuum lines with pump.
Cleared codes and drove around the block, SES on again and show's only
code 33. Possibly did not run it far enough to set 78.
How do I test the baro before buying a new one?
gmctd
03-24-2005, 08:11 AM
Could be your EGR Vent Solenoid is stuck - or the Apply solenoid is sticking
GM Service suggest trying another sensor, comparing the results.
The sensors are cheap, and operate within certain broad limits - one could be at lo-limit, other could be at hi-limit, totally dissimilar readings, both acceptable.
The sensor on the intake is the Boost - the firewall mounted sensor is EGR, with the long vacuum tube to the EGR Vent Solenoid.
quantum mechanic
03-24-2005, 08:21 AM
The Baro has to read ~20" hg vac for all to work right.
steelydan
03-24-2005, 07:56 PM
Well checked everything again, decided to plug vacuum guage into solenoids to check vacuum. Guess what.... No vacuum. Checked it at pump, no vacuum. Vacuum pump is 3 months old. Pulled it off and took it back. Replaced under warranttee, 3rd one in 8 months. Installed it and good to go. All were re-mans... all hooted when new but this one is quiet.... Hopefully I got a good one...
Thanks for the replies Gentlemen! Dan
ssorange
03-25-2005, 07:25 PM
To get code 78 the following is required:
RPM greater than 1800.
Fuel rate greater than 20 mm.
Boost pressure greater than or less than desired
Hope this helps
-John
Texas Diesel Guy
03-25-2005, 07:29 PM
...I think he found the problem, his new vacuump pump failed.