How to Turn-Off the Air Bag Light /
Clearing Diagnostic Code 41
1990-1994 Lexus LS400
If the air bag light stays on in your instrument cluster this usually indicates a problem somewhere in the air bag system. However, for some reason, if you remove the instrument cluster and turn on your car while the cluster is disconnected the air bag light will stay on. The repair manual calls this a "Code 41 - Malfunction stored in memory." Obviously this little light is really annoying; here's how to turn it off.
Here's a picture of the problem.
1) Connect two wires long enough to reach the ground/floor to terminal Tc and AB of the TDCL port. The TDCL port is located under the driver's side right above the parking brake. In this picture the blue wire is connected to terminal Tc and the red wire is connected to terminal AB.
2) Connect a wire long enough to reach the ground/floor to a grounded point on your car. I connected this green wire to the bolt that holds the driver's side courtesy switch on using an alligator clip. Just lift up the bottom section of the rubber cover to see it; sorry about the blurry pic.
3) Turn the ignition switch to ACC or ON and then wait at least 6 seconds.
4) Now you need to do what I call "the wire dance." You're going to alternate touching the ends of the Tc and AB wires to the ground wire. Let the ground wire lay on the floor then you can easily touch the Tc and AB wires against it.
Start by touching the end of the Tc wire to the ground wire for one second. After a second, instantly remove the Tc wire and replace it with the AB wire touching the ground wire for one second. Now instantly replace it with the Tc wire for the 3rd second, then instantly replace it with the AB wire for the fourth second. Finally, instantly replace the AB wire with the Tc wire and hold the Tc wire on the ground wire for several seconds. After several seconds the air bag light will blink fast in a 64msec cycle, this means code 41 has been cleared.
So if that didn't make sense here's the short version:
Tc + ground, AB + ground, Tc + ground, AB + ground, Tc + ground and hold.
-This is all about timing. When touching the wires for one second you have a plus or minus 0.5 second margin of error (so you need to hold the wire 0.5 to 1.5 seconds); this means you don't need to be exact. What I did was count slowly "one one thousand," after that you instantly switch the Tc and AB wires.
-When I say instantly I mean instantly. You only have 0.2 seconds to switch the wires. So right after you remove one wire have the other wire touching. Instantly. If you don't switch the wires fast enough the air bag light will blink out a code 41. A code 41 is 4 slow blinks a little space and then a fifth blink. If you get the proper timing the air bag light blinks really fast and then the light goes out.
-If you don't get it keep trying. This procedure took me at least ten tries before I found the correct timing. You don't need to disconnect the wires from the port either, just try the wire dance again.
5) Once the code is cleared disconnect the wires and close up the TDCL port.
And it's gone!
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