C1201 Toyota Trouble Code Repair
Diagnose and fix a C1201 Toyota trouble code
A C1201 Toyota trouble code can be very difficult to diagnose and fix because it’s such a general trouble code
C1201 Engine Control Malfunction
If you didn’t know where to start, you’d assume you’ve got an engine computer/sensor issue and that can have you chasing down a rabbit hole. But there is a hint here of where to start. When you look up C1201 in a professional shop manual, the code is listed in the Vehicle Stability Control section of the manual. Ah HA! It has something to do with the stability control system. But what?
How Toyota vehicle stability control works
The Toyota stability control system gets inputs from the yaw sensor, deceleration sensor and the ABS system. The ABS system gets its inputs from the wheel speed sensors. Wheel speed sensors have a pretty high failure rate, but when they fail, they usually set an ABS-related trouble code. So don’t go chasing wheel speed sensor issues if all you get is a C1201 code.
If the Toyota vehicle stability control system senses a wheel lock, a deceleration sensor or yaw sensor signal that indicates the vehicle is encountering a skid, swerve or is somehow going out of control, it operates the ABS brakes and reduces engine power to try and bring it back under control. Great, how does that relate to a C1271?
Common cause of a C1201 Toyota trouble code
If you perform any work on the steering, suspension or sensors, you can inadvertently set a C1201 Toyota trouble code.
In order for the stability control system to work properly, it must know what the yaw and deceleration sensors report when the vehicle is stopped on a level surface. That’s referred to as a calibration procedure or zero point calibration. The calibration can be performed with or without a scan tool.
Perform a zero point calibration on Toyota to correct C1201 trouble code
Park the vehicle on a level surface with no more than a 1° inclination. During the zero point procedure, do not vibrate the vehicle by tilting, moving or shaking it. Do not start the engine during the zero point calibration procedure.
Clear the zero point calibration data
1. Turn the ignition switch to ON.
2. The warning lights and indicator lights will come on for 3 seconds to indicate that the initial check is completed.
3. Using a jumper, connect and then disconnect terminals 12 (TS) and 4 (CG) at the data link connector 4 times or more within 8 seconds.
Toyota C1201 zero point calibration. Data Link Connector terminals
4. The “SLIP” warning light should come on. If it does not, repeat the procedure.
NEXT
5. Turn IGN switch to OFF. Make sure shift lever is in Park. Apply the parking brake.
6. Connect terminals 12 (TS) and 4 (CG) at the data link connector
7. Turn the IGN switch to ON
8. The “SLIP” warning light should blink. If it doesn’t blink, perform the zero point calibration (6) again.
9. Turn IGN switch to OFF
, 2018
