Intermediate Speed Sensor (ISS) Malfunction
Your transmission's intermediate speed sensor isn't sending the right signal to the engine computer, like a speedometer that's stuck or giving wrong readings. This prevents the transmission from shifting smoothly because it can't tell how fast the internal gears are spinning.
The ECU monitors the Intermediate Speed Sensor (ISS) output voltage to track transmission internal shaft speed. It compares the ISS signal against expected RPM ranges during shifts and compares it to other speed sensors for consistency. If the signal is missing, erratic, or outside normal operating voltage, the ECU sets this fault code.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| ISS Signal Voltage | 0.5–4.5 volts (variable with shaft speed) | Below 0.2V, above 4.8V, or no signal detected |
| ISS Plausibility Check | ISS RPM within ±15% of calculated transmission input speed | ISS RPM deviates >20% or contradicts other sensors |
Code P1765 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1765 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.