Beware of Code P0720 - Transmission Digest

Beware of Code P0720

Subaru’s TG5D9 transmission utilizes four different speed sensors, two of which are inside the transmission and two are externally located. When a code P0720 for a front vehicle speed sensor is set, the most-forward external speed sensor is replaced – yet the code remains. The wiring is checked and the signal is checked and all looks fine. The TCM then gets replaced but P0720 remains.

Beware of Code P0720

Shift Pointers

Author: Wayne Colonna
Subject: Subaru TG5D9 unit
Issue: Wrong speed sensor

Shift Pointers

  • Author: Wayne Colonna
  • Subject: Subaru TG5D9 unit
  • Issue: Wrong speed sensor

Subaru’s TG5D9 transmission (Figure 1) utilizes four different speed sensors, two of which are inside the transmission and two are externally located. When a code P0720 for a front vehicle speed sensor is set, the most-forward external speed sensor is replaced – yet the code remains. The wiring is checked and the signal is checked and all looks fine. The TCM then gets replaced but P0720 remains.

The problem is the wrong speed sensor being addressed.

The most front external speed sensor is called “turbine speed sensor 1” (Figure 2).

The most rear external speed sensor is called “the rear vehicle speed sensor” (Figure 3).

Inside the transmission located on the valve body is “turbine speed sensor 2” (Figure 4).

The remaining internally located speed sensor is fitted in the rear of the transmission. It reads the teeth on a gear that is used to drive the front pinion gear (Figure 5).

This speed sensor is called the “front vehicle speed sensor.” For obvious reasons one can easily conclude why this sensor located inside in the rear of the transmission would not be thought of as a front vehicle speed sensor. It is this sensor that produces code P0720. “Turbine speed sensor 1” produces code P0715, “turbine speed sensor 2” produces P1710, and the rear vehicle speed sensor produces code P1706.

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