Fault code 12

[Graham d]

I have 1998 with the 7A-Fe engine if I have read fault correctly it 12 has anyone come across this. Missfire above 3500 with and without load. I am told that it was fitted with new ignition switch as it starts first time from cold but won't start once warm straight away but after a short while. At one time whilst waiting to restart I heard a click like a relay from area of internal fusebox. Sparkplugs are new - any thoughts Thanks

[Konrad C]

I referred to some info and code 12 is one of the following: Crankshaft position sensor or camshaft position sensor, circuit malfunction. Open or short in the crankshaft/camshaft position sensor circuit, crank or camshaft sensor, starter or engine ECU.

From your description, it sounds like either the crankshaft or camshaft is not working properly. Check the connections.

I would check the vacuum system too, making sure there are no leaks.

Have you tried pulling the EFI fuse for about 30 seconds. It is located in the engine compartment fuse box. It will reset the ECU back to learning mode. 

[Graham d]

Thanks Konrad - I have replaced the camshaft position señsor (secondhand). I was thinking a bad connection - I will look at the weekend.

 

[Devon Aygo]

Toyota list code 12 as a fault within the distributor system indicating a loss of signal between distributor & engine ECU for more than 2 seconds once the car is running.

Toyota list the following as potential for concern:

* Open or short on ECU harness wires G or NE ( Distributor to ECU )

* Distributor 

* Open or short in STA ( Starter relay ) circuit

* Engine ECU

 

[Konrad C]

Lee is correct! 

Code 12 is rpm and also knock sensor. I could not find the code I had. I went to a more complicated source, but here is a more straight forward list.

http://www.troublecodes.net/toyota/

Everything seems to tie into timing. 

I had a problem with third party HT leads, and went back to originals. The plugs are deep in the engine, and original leads had a firm connection on the plugs. I had two sets of third party that seem to loose firm contact with the plugs. Also the leads could breakdown. 

[Elvir]

I have a corolla 1997 model it show the code 12 so i replace the distributor after that the car stil dont want to start i check for error codes again and it stil show the same code i have check for lose connection bt all is fine... WhAt can it stil be plz help?