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Mitsubishi Triton GLX 2011 - Diagnosing P1782 and P1766 Transmission Codes After Filter Change

Model: Mitsubishi Triton GLX Fault Code: P1766 Posted: 2016-05-24 23:18

I'm seeking advice on two transmission fault codes that appeared unexpectedly in my 2011 Mitsubishi Triton GLX after performing a transmission filter and oil change. The codes are P1782 (Incorrect 4th Gear Ratio) and P1766 (Input Shaft Speed Sensor Malfunction). The issue emerged suddenly—no wiring was disconnected, and no metal particles were found in the oil pan during inspection. This makes an internal transmission failure seem unlikely, especially given that the problem only occurred after a filter kit was installed. While most online sources suggest internal transmission damage as the root cause, I'm wondering if there are other possible explanations? Could the filter kit or fluid type be contributing to the fault? Any insights or troubleshooting steps would be greatly appreciated. Thank you for your help.

Related fault codes
P1766P1782
Comments (5)
Anonymous 2016-05-25 08:09

The vehicle was running normally before the transmission filter and oil change. Could you clarify what 'running a filter kit through the transmission' entails? Also, please confirm that the correct fluid type (e.g., Dexron III) and proper installation procedures were followed during the service.

Anonymous 2016-05-25 15:10

The filter was installed correctly, and premium Dexron 3H fluid was used as recommended in the service manual.

Anonymous 2016-05-25 15:38

That's the only plausible connection I can think of—could it be related to the filter kit installation or compatibility? I performed a quick diagnostic check, and the fault codes don't appear to be specific to North American models; they may be more widespread across global variants.

Anonymous 2016-05-25 15:58

I'm in Australia and driving a common model here. However, some sources indicate that P1782 and P1766 are relatively frequent codes across various Triton models—though I'm not certain if this applies to all markets or years.

Anonymous 2016-05-25 23:17

I suspect a rare case of misdiagnosis. After rechecking the transmission pan, filter, and solenoids—all tested fine—I refitted everything and topped up with fresh oil. A test drive showed no fault codes returning. Still baffling—what could have caused this sudden appearance?