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Toyota C1201 code fix

Fix a Toyota C1201 code

A C1201 Toyota trouble code can be very difficult to diagnose and fix because it’s such a general trouble code. The is defined as “Engine Control Malfunction.” Right. Not a lot to go on.

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 let’s look up the code in a shop manual

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

So it obviously has something to do with the stability control system. But why is it defined as an Engine Control Malfunction

First, let’s look at how Toyota vehicle stability control works

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 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?

You or the shop probably caused the C1201 code when working on the steering or suspension system

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

If you moved the steering wheel while working on the vehicle, you forced it out of calibration and that’s what set the code.

Fix a Toyota C1201 trouble code 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 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

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

Posted on by Rick Muscoplat

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