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C1201 is a secondary code. It means the ECU is not talking. There should be a primary code that indicates the actual failure. You may want to have a proper toyota tech check it.
Who is "they" - who hooked up the diagnostic thingy. If "they" is an auto parts house, all they can give you is the codes. You have to have the codes interpreted and see if they are related. Don't just start throwing parts into the vehicle. The transmission shop was probably right - it's an electrical issue. You need to take your vehicle to a dealership or a qualified, experienced independent shop and invest in some diagnostics.
Possible causes
Faulty Ignition Coil 1
Ignition Coil 1 harness is open or shorted
Ignition Coil 1 circuit poor electrical connection
Faulty Engine Control Module (ECM)
What does this mean? When is the code detected? Each ignition circuit is continuously monitored by the Engine Control Module (ECM). The test fails when the ECM does not receive a valid pulse signal from the ignition coil. Possible symptoms Engine Light ON (or Service Engine Soon Warning Light) Lack/Loss of Power Engine may be harder to start Engine hesitation Rough engine idle P0351 TOYOTA Description: The ignition system on the vehicle uses individual ignition coils for each cylinder. The Engine Control Module (ECM) controls each ignition coil operation. The ECM sends a ON/OFF signal to energize the ignition coil to create a spark at the spark plug when a spark is required at the cylinder.
C1201 error code means that you have some problem in engine control system.
Possible causes for P0421 error
Warm Up Three Way Catalytic converter deterioration or malfunction
Exhaust system leaks
Loose front or rear HO2Ss
Faulty front heater O2 sensor
O2 sensors harness is open or shorted
O2 sensors poor electrical connection
The P0421 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem.
that code 356 is a bad coil. if it is completely dead than you now have a 5 cylinder car.... very bad not only on mpg but also on the life of the engine. when you have a "dead hole" it can affect the other cylinders and you have misfire codes for all 6..... this could mean you simply need a tune up or that there is something affecting all cylinders. check for a vacuum leak after the air flow sensor, or a ruptured fuel pressure regulator (remove the vacuum line at the regulator and smell for gas cause there should not be gas on that side of the diaphragm) fouled spark plugs, clogged exhaust or catalytic converter, stuck open or dirty EGR valve to name a few. change that #6 coil first and at least inspect or change the spark plugs... c1201 relates to a communication stop between ECU's , don't assume that as the vsc lights etc were illuminated then that is the system that is faulty. It is most likely that the fault is within the engine system but with vehicles equipped with vsc all systems are linked so a fault with one will log a code in all others ( normally a communication stop code as you have)
I would advise fixing the engine codes first then get the other systems checked out
hello, this code usually comes up in conjunction with another code, it just means that another computer on the car can not communicate with the ECM, are there any other codes besides this, is the abs/VSC, TRac cruise control or 4x4 lights on?
HI WILL NEED AN ENGINE CODE TO BE CERTAIN
BUT SHOULD BE 1-2-3-4-5-6
IT SOUNDS DAFT BUT THAT IS FOR ENGINE CODES 5VZ-FE AND 1MZ-FE AND 3VZ-FE
ALL ARE V6 ENGINES WITH THE SAME FIRING ORDER CYLINDER NUMBERS ARE ARRANGED LIKE THIS 1 3 5
2 4 6
FRONT
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