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B1270 OBD-II Trouble Code: Servo Motor Potentiometer Defrost Circuit Short to Battery

diagnostic check engine light

B1270 code definition

The B1270 trouble code identifies a malfunction with the servo motor potentiometer defrost circuit.

What the B1270 code means

The B1270 code is a generic OBD-II trouble code that detects an error with the servo motor potentiometer defrost circuit. The potentiometer controls voltage output into the defrost system, which allows the defroster to operate on a scale, rather than just on or off. When a circuit error is detected from the servo motor potentiometer, then the B1270 trouble code will be stored.

What causes the B1270 code?

Potential causes of the B1270 trouble code include:

What are the symptoms of the B1270 code?

The B1270 code may be accompanied by the check engine soon Warning Light, or a flashing climate control light. It is common for the defroster to not work properly when this code is detected.

How does a mechanic diagnose the B1270 code?

The B1270 code will be diagnosed using a standard OBD-II trouble code scanner. A trustworthy mechanic will use the scanner to view the freeze frame data, and gather information about the code. The mechanic will also look to see if any other codes have been detected. In the event that there are numerous codes present, then the technician will need to address them in the order in which they are displayed on the scanner. The codes will then need to be reset, and the vehicle restarted, to see if the B1270 code returns. If not, then it was most likely triggered inaccurately, or represents an intermittent error.

If the B1270 code remains detected, then the mechanic will need to visually inspect the electrical components associated with the defrost system. All fuses, wires, and connectors should be examined, and the circuit will then need to be tested. Next, the servo motor and potentiometer will be thoroughly inspected.

After any replacements or repairs, the mechanic should reset the trouble codes, restart the vehicle, and check to see if the B1270 code is still detected. This helps the mechanic know when the issue is resolved.

Common mistakes when diagnosing the B1270 code

The most frequently made error when diagnosing the B1270 code is the failure to properly abide by the OBD-II diagnosis protocol. It is extremely important that mechanics follow the protocol at all times, to ensure that all diagnoses and repairs are efficient and accurate.

Often servo motors and potentiometers are unnecessarily replaced before electrical components are inspected.

How serious is the B1270 code?

The B1270 trouble code won’t keep a vehicle from being drivable, but it may keep the defrost system from working. The defrost system is an important safety feature that can greatly aid driver visibility, so a vehicle with this code should be inspected as soon as it is convenient.

What repairs can fix the B1270 code?

Potential repairs for the B1270 code are:

  • Potentiometer replacement
  • Servo motor replacement
  • Replacement or repair of electrical components, including the circuit
  • In rare cases, replacement of the climate control module, body control module, or PCM

Additional comments for consideration regarding the B1270 code

It is extremely rare for the B1270 code to be triggered by a defective control module, so all potential causes of the code should be checked before a failed PCM, body control module, or climate control module is suspected. In the unlikely event that a control module does need to be replaced, it will also need to be reprogrammed.

Need help with a B1270 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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