FAQ Frequenly Asked Technical Questions. This section is read only, and posts are made by the staff. If you have something to contribute contact any moderator.

4.5 Caddy (1990) Diverter Valve Repair

Old 03-24-2015, 06:57 PM
Junior Member
Thread Starter
Join Date: Mar 2009
Posts: 26
Default 4.5 Caddy (1990) Diverter Valve Repair

My fuel trim on my left (front) bank had been skewing very rich. I diagnosed this as the O2 reading lean. I also received the E049 code (diverter valve). I followed the diagnostic tree per the FSM, and discovered that when then valve divertered air front the exhaust manifold (cold start) to the cat (warm engine), air continued to bleed from the valve to the exhaust manifold, thus leaning the front bank mixture and PCM compensating by enriching the fuel trim.

I located a diverter valve at my local junkyard, replaced it, as well as both check valves. Car is back to normal.

However, I have my old diverter valve. Both solenoids are good, functional, and test at ~ 30 ohms. They click, seal, and work fine (I tested them as well by applying power to them and vacuum. From what I understand, the most common fault of the valve is that the check valve goes bad, and allows hot exhaust gas to enter the valve, destroying the diaphragm(s). However, I have taken mine apart. I am attempting to repair the valve. Reassembly will not be an issue as to the method I have used to disassemble.

What disturbs me is that both diaphragms are well intact. I will post pictures of the unit. What am I over looking here? Any help I would appreciate. I assume there must be something else wrong, requiring even further dis-assembly. Knowledge of the exact physical operation of the valve will be helpful. Thank you.

View image: 2005 03 08 00 57 53
View image: 2005 03 08 00 58 00
View image: 2005 03 08 00 58 09
View image: 2005 03 08 00 58 20
View image: 2005 03 08 00 58 34

Old 03-25-2015, 11:57 PM
Junior Member
Thread Starter
Join Date: Mar 2009
Posts: 26


Although this diverter valve was only used on the 4.5 (and 4100?) to comply with emissions by use of the air (smog) pump - nobody probably will take notice of this thread as these cars are now exempt from emissions. However, even with the valve and/or pump removed, there is no way around fooling the ECM and unless you want to remove your SES light, the car (if not already in a junk yard) will consistently throw a code.

Further dis-assembly revealed a piece of a plastic (as indicated where my pen is pointing) jamming up the valve. The piece of plastic is actually a piece of a pump vain when my air pump had blown up. Debris had entered the valve.

I cleaned and added trace amounts of fel-pro to the shaft.

To prevent this from ever happening again, I have decided to add another check valve (like the one from the valve to the exhaust manifold) in-line from the pump to the valve to prevent any debris from entering the valve.

View image: 2005 03 09 06 02 37
Related Topics
Thread Starter
Last Post
Private For Sale/Trade Classifieds
04-02-2015 01:54 AM
Cadillac Deville
04-20-2012 11:10 PM
General Tech
06-19-2011 11:03 AM
Cadillac Coup DeVille
06-13-2011 01:31 PM
Private 'Wanted' Classifieds
07-26-2008 05:23 PM

Thread Tools
Search this Thread
Quick Reply: 4.5 Caddy (1990) Diverter Valve Repair

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.