Code 28
Thread Starter
Safety Car
Joined: Aug 2000
Posts: 3,507
Likes: 0
From: Easton CA
Code 28
According to the 1992 Corvette service manual, a code 28 involves "Quad-Driver Module (QDM) #3 5.7L (VIN P) "Y" Carline (Port)". This controls the fan switches and A/C clutch control relay. I have a manual switch to turn the fans on and off; the only time I use it is if I am running around in town in stop and go traffic. Could this be the reason the ECM is recording a code 28? When the switch is set in the normal operating position (off), the fans will operate at the correct temperatures.
Thanks.
1992 LT1
Thanks.
1992 LT1
Melting Slicks
Joined: Apr 2002
Posts: 2,546
Likes: 0
From: Orlando FL
Re: Code 28 (Oly)
dont sure about the code 28.. never heard that one before... an TTT mean to the top.. users type this into a new post to cycle the question to the top.. otherwise it finds its way to 3 or 4 pages into the forum.. :jester
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 12
The code 28 involves the #3 circuit which involves the A/C clutch relay and the 2 cooling fan relays
http://forums.corvetteforum.com/1554702604-post3.html
Others have had the code with man fan operation
http://forums.corvetteforum.com/1554768822-post17.html
so I suspect manually operating the fans upsets the ECM because the fans are running without the ECM telling them to so it throws the code
For a code 26 but same principle
http://forums.corvetteforum.com/c4-t...river-4-a.html
http://forums.corvetteforum.com/1554702604-post3.html
Others have had the code with man fan operation
http://forums.corvetteforum.com/1554768822-post17.html
so I suspect manually operating the fans upsets the ECM because the fans are running without the ECM telling them to so it throws the code
For a code 26 but same principle
http://forums.corvetteforum.com/c4-t...river-4-a.html
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Usually a quad driver fault is caused by one of the circuits it drives drawing too much current.
A quad driver turns on 4 different circuits, usually relays or solenoids. The way to approach this is to first determine which 4 things are controlled by that quad driver and then disconnect them one by one, reset the ECM, and then check to see if the error code returns.
A quad driver turns on 4 different circuits, usually relays or solenoids. The way to approach this is to first determine which 4 things are controlled by that quad driver and then disconnect them one by one, reset the ECM, and then check to see if the error code returns.
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Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 12
He knows what is causing the code , the manual switch he is using to bypass ECM control of the fans.
As per the link , the code goes away when the ECM has control of the fans
