1994 Lexus ls 400 After replacement of Alt, check engine light came on (code 71 ,45) .Did not even drive it.
No Problems before .Car runs fine, no idle or drivavailability problems . ???? Coincident of what ?

 

Is the ambient temp sensor reading correctly in the car? The sensor is in the front right section of the car ahead of the radiator. Perhaps you did something to it while changing the alternator? Or it's just a glitch when you disconnected the battery. Clear codes and see if it goes away. The P0045 is a boost control flag, so that sounds totally bogus.

 

Did you disconnect both battery terminals before the alternator R&R? Most instructions say to remove the ground cable, but I believe it is a good idea to remove both on cars with all these electronic gadgets, computers, etc. (especially for alternator or starter R&R). Of course, that is hindsight now. Here is what I suggest:

• · Disconnect both terminals on the battery (always disconnect negative cable first)
• · Make sure battery is fully charged
• · Clean both terminals on battery
• · Clean both battery terminal cable connectors
• · Apply grease to battery terminals (or oil)
• · Reconnect terminals starting with positive cable first

*If you have done all this already and know the battery is fully charged then just disconnect the cables, wait 10 minutes or so, and reconnect everything.

 

Code 47 & 71 do you know readings for egr step motor-Note : Does not have modulator !