P1684 Code failures by brands


Description of DTC code P1684

The Transmission Control Module (TCM) is an electronic component in charge of understanding the electrical signals from sensors and other devices related to transmission performance. There are some of these sensors that work closely with the TCM, which collects information about the vehicle performance, and then they send data to the TCM, which uses it for the most appropriate gear shift calculation.

The TCM Ignition Temperature Sensor that is installed inside the control solenoid valve assembly (with body and TCM) has no repairable parts. Its function is to provide the temperature of the TCM when the controller is turned on. These readings are used in various control module software travel and diagnostic routines. A failure of this system is handled internally in the TCM, which is why it has no external circuitry involved.

When the diagnostic code P1684 OBD2 is set on vehicles from the manufacturers Buick, Cadillac, Chevrolet or GMC, it means that performance problems have been discovered in the TCM's Ignition Temperature Sensor circuit.

Symptoms of fault code P1684

  • Check Engine lamp on.
  • When trying to shift from a lower gear during acceleration the response is delayed.
  • You cannot leave the neutral mode.
  • Shifting from one gear to another is random.

Causes of OBD2 P1684

The factors by which the fault code P1684 OBDII is configured are the following:

  • Other DTC codes that indicate TCM failures may cause P1684 to be established.
  • The TCM's Ignition Temperature Sensor assembly may be damaged.
  • The Transmission Control Module may be damaged.

Possible solutions of the DTC code P1684

To solve the DTC code P1684 OBD2, consider the following:

  • As a first step, consult the Technical Service Bulletins. The problem your vehicle is having may be known to the manufacturer and useful information is included in these bulletins.
  • Use an automotive scanner to check if other error codes are set, especially those that signal specific TCM If so, diagnose these codes first.
  • If you don't discover additional codes to the P1684, it is likely that the TCM has programming errors or other damage. It is recommended that you attend an advanced service center.

Codes related to P1684

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