Error Code P1776 is defined as Transmission Control Switch Circuit is Out of Self-Test Range. It is set when the KOER (Key On Engine Running) self-test Transmission Control Switch (TCS) is not cycled.
This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Ford, Toyota, BMW, Chrysler/Dodge/Jeep, Citroen/Peugeot, Daewoo, GM, Lexus, Lincoln, Mazda, Mercedes, Nissan, Volvo, etc. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.
As said earlier, this code is set during Key On Engine Running test, when the switch is not cycled during the test. This happens when you don’t cycle the O/D switch on and off.
As with any other error codes, this code activates the Check Engine light and registers the error code in the vehicle’s system. Other symptoms include engine misfire.
TCS not cycled during self-test is the most common cause for this error code. Other reasons include:
- Faulty TCS
- Open or shorted harness in TCS
- Poor electrical connection in TCS circuit
How to Check
To test this code, erase the code and then retest.
If the code comes back after you have done the KOER test, then you may have a problem with either a short in the O/D switch or the switch itself has gone bad.
How to Fix
The common repair for this error code is replacing the TCS. Another repair of course, requires you to repair or replace the open or shorted TCS or faulty electrical connection on its circuit.
If you have just recently replaced the fuel injector, there’s a good chance you may get this error code. If that is the case, check the cylinders if they’re low.
If you have low cylinder problems, check the valves that cause the misfires and lower compression readings, as this may suggest a valve issue. Verify the issue by conducting a wet compression test. You can do this by squirting a few drops of oil into the cylinder and see if the compression comes up. If it does, then you have a problem in the bottom end/rings/piston.
If that is the case, then it’s best to take your vehicle to the machine shop or have the cylinder head replaced. Check out your vehicle’s technical service bulletin for cylinder head replacements.
Most often than not, this error code is caused by simply not performing the test correctly.