Check Engine light on 2005 Toyota Echo, Code P0012

it was probably a temporary bad connection to the sensor and it just needed to be shaken about to reconnect

In my wife's case it was that the neck of the filler (where it contacts the gas cap) rusted. It didn't allow a good seal. Since it was a 2005 we also replaced the gas cap in 2013.

P0012 - "A" Camshaft Position - Timing Over-******** (Bank 1)
OBD-II DTC Trouble Code Description

"A" Camshaft Position - Timing Over-******** (Bank 1)
What does that mean?

A code P0012 refers to the VVT (variable valve timing) or VCT (variable camshaft timing) components and the car's PCM (powertrain control module, also called an ECM). That consists of a few different components but the P0012 DTC specifically refers to the camshaft (cam) timing. In this case, if the cam timing is over-********, the engine light will be illluminated and the code will be set. The "A" camshaft is either the intake, left, or front camshaft.
Potential Symptoms

Most likely a P0012 DTC will result in one of the following:

hard starting
poor idle and/or
stalling

There are potentially other symptoms as well. Of course, when trouble codes are set, the MIL (malfunction indicator lamp, a.k.a. the check engine light) illuminates.
Causes

A P0012 DTC trouble code may be caused by one or more of the following:

Incorrect camshaft timing
Wiring problems (harness/wiring) in intake timing control valve control solenoid system
Continuous oil flow to VCT piston chamber
Failed timing valve control solenoid (stuck open)

Possible Solutions

The main thing to check is to verify the operation of the VCT solenoid. You're looking for a sticking or stuck VCt solenoid valve caused by contamination. Refer to vehicle specific repair manual to perform component tests for the VCT unit. Notes: Dealer techs have advanced tools and the ability to follow detailed troubleshooting steps, including the ability to test components using a scan tool.

the engine light on means your car has the obd2 code problem you need to check out the code and delete it, i know this tool is helpful for your car, or you can take your car to toyota dealer to read out the code.

P0015 "B" Camshaft Position -Timing Over-Retarded (Bank 1) - See Trouble Code P0012
P0012 "A" Camshaft Position - Timing Over-Retarded (Bank 1)

Would need your Mazda car/truck model/model year/engine type (8th digit of VIN), to
look up what sensors/conditions light your dashboard transmission light...

The check engine light will come on for many different reasons. Could be as simple as a loose gas cap. If that's not the problem, then you need to get the code(s) read. Your car will require an OBD II code reader. In some states, the auto parts stores will retrieve the codes for you. Without a code, there is no way to say what made the light come on for sure.

i looked up trouble code P0012 for Camshaft position ”A” −timing over−retarded (BANK 1). Possible causes include: valve timing, oil control valve, oil control valve filter, camshaft timing gear assembly, or your engine control module.

Look for water entry into the front crash sensors behind the front bumper. They have bright yellow connectors.

go to any kragen or autozone parts store, they will run the test for trouble code that turned light on for free, tell them u want an OBD 2 trouble code test, then post the code here.

Check engine light on with