Cadillac Repair: 91 Fleetwood check engine light, egr solenoid, power steering rack

Question
The "check engine soon" light on my 91 Fleetwood 4.9 engine Cadillac revealed codes E40 & E48.  A new EGR valve seemed to take care of the E48 problem.  The E40 problem was checked out and led to a blown 15 amp fuse (Fuse #5) in the relay center beneath the glove box.  A check for "short to ground" could find no short.  A new fuse lasted only a short time before blowing.  The wiring was checked again and no short was found.  A new fuse was installed and the vehicle was road-tested over rough terrain and the fuse did not blow.  However, 40 miles later the fuse is blown again.  When the fuse blows, the check engine light comes on and the car loses its normally "peppy" acceleration.  The codes are now E40 and E52.  Any suggestions?  My mechanic has been left scratching his head.

Answer
This fuse controls:

1. Power steering switch. Wire colors are Pink/Black and Light blue/orange.

Check the wires that go to the switch at the power steering rack for short to ground. May be rubbibg against firewall or intermittently touching the exhaust.

2. EGR solenoid. Wires are Pink/black and gray.

3. Canister Purge solenoid. Wire colors are Pink/black and dark green/yellow.

4. Transmission electrical solenoids.

Does the fuse blow ONLY when you drive the car ?. try just starting the car and turn the steering wheel from right to left numerous times and see if the fuse blows and try accelerating and decelerating the engine while in park.

See if the fues blows just before the transmission is ready to shift into the next gear.

When the fuse blows the transmission does not shift correctly as it is tied into the same fuse as all the 1 thru 3 items.