How to fix a Toyota C1201 code without getting sidetracked

Learn the most common cause and fixes for a Toyota C1201  Code

A Toyota C1201 code can be very difficult to diagnose and fix because it’s such a general trouble code. It is defined as “Engine Control Malfunction.” There’s not much to go on, right?

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 it’s usually not the ECM. Instead, it’s most often a calibration issue that you caused. Here’s the scoop on a Toyota C1201 code; what causes it and how to fix it

A Toyota C1201 code is listed in the Vehicle Stability Control section of the shop manual

So it has something to do with the stability control system. The Toyota stability control system gets inputs from the yaw sensor, the 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-up, a deceleration sensor, or a 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 to bring it back under control. Great. How does that relate to a C1271 code?

You or the shop probably caused the code when working on the steering or suspension system

If you move the steering wheel while working on the vehicle with the engine off, you forced it out of calibration. When you start the engine, you’ll get the warning light and C1202 code.

If you perform any work on the steering, suspension, or sensors, you can inadvertently set a C1201 Toyota trouble code. How? Well, 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.

Fix it by performing a zero-point calibration to

• 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 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 the IGN switch to OFF. Make sure the 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 the IGN switch to OFF

The code should be cleared

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