diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index a12e5893dc..f9b0a00019 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -878,8 +878,6 @@ class UTF16LETest(ReadTest, unittest.TestCase):
     encoding = "utf-16-le"
     ill_formed_sequence = b"\x80\xdc"
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_partial(self):
         self.check_partial(
             "\x00\xff\u0100\uffff\U00010000",
@@ -922,10 +920,6 @@ def test_nonbmp(self):
         self.assertEqual(b'\x00\xd8\x03\xde'.decode(self.encoding),
                          "\U00010203")
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
-    def test_incremental_surrogatepass(self):
-        super().test_incremental_surrogatepass()
 
 class UTF16BETest(ReadTest, unittest.TestCase):
     encoding = "utf-16-be"
diff --git a/common/src/encodings.rs b/common/src/encodings.rs
index 39ca266126..e0075ad1eb 100644
--- a/common/src/encodings.rs
+++ b/common/src/encodings.rs
@@ -633,3 +633,176 @@ pub mod ascii {
         )
     }
 }
+
+pub mod utf16_le {
+    use super::*;
+
+    pub const ENCODING_NAME: &str = "utf-16-le";
+
+    pub fn encode<Ctx, E>(mut ctx: Ctx, errors: &E) -> Result<Vec<u8>, Ctx::Error>
+    where
+        Ctx: EncodeContext,
+        E: EncodeErrorHandler<Ctx>,
+    {
+        let mut out = Vec::<u8>::new();
+        loop {
+            let data = ctx.remaining_data();
+            let error_info = {
+                let mut iter = iter_code_points(data);
+                iter.find(|(_, c)| c.to_u32() > 0x10FFFF)
+            };
+            let Some((i, ch)) = error_info else {
+                break;
+            };
+
+            // Add valid part up to the error
+            for ch in data[..i.bytes].code_points() {
+                let ch_u32 = ch.to_u32();
+                if ch_u32 <= 0xFFFF {
+                    out.extend_from_slice(&(ch_u32 as u16).to_le_bytes());
+                } else if ch_u32 <= 0x10FFFF {
+                    let code = ch_u32 - 0x10000;
+                    let high = 0xD800 + (code >> 10);
+                    let low = 0xDC00 + (code & 0x3FF);
+                    out.extend_from_slice(&(high as u16).to_le_bytes());
+                    out.extend_from_slice(&(low as u16).to_le_bytes());
+                }
+            }
+
+            let err_start = ctx.position() + i;
+            let err_end = StrSize {
+                bytes: i.bytes + ch.len_wtf8(),
+                chars: i.chars + 1,
+            };
+            let err_end = ctx.position() + err_end;
+            let replace =
+                ctx.handle_error(errors, err_start..err_end, Some("surrogates not allowed"))?;
+            match replace {
+                EncodeReplace::Str(s) => {
+                    // Re-encode the replacement string
+                    for cp in s.as_ref().code_points() {
+                        let cp_u32 = cp.to_u32();
+                        if cp_u32 <= 0xFFFF {
+                            out.extend_from_slice(&(cp_u32 as u16).to_le_bytes());
+                        } else if cp_u32 <= 0x10FFFF {
+                            let code = cp_u32 - 0x10000;
+                            let high = 0xD800 + (code >> 10);
+                            let low = 0xDC00 + (code & 0x3FF);
+                            out.extend_from_slice(&(high as u16).to_le_bytes());
+                            out.extend_from_slice(&(low as u16).to_le_bytes());
+                        }
+                    }
+                }
+                EncodeReplace::Bytes(b) => {
+                    out.extend_from_slice(b.as_ref());
+                }
+            }
+        }
+
+        // Process all remaining data
+        for ch in ctx.remaining_data().code_points() {
+            let ch_u32 = ch.to_u32();
+            if ch_u32 <= 0xFFFF {
+                out.extend_from_slice(&(ch_u32 as u16).to_le_bytes());
+            } else if ch_u32 <= 0x10FFFF {
+                let code = ch_u32 - 0x10000;
+                let high = 0xD800 + (code >> 10);
+                let low = 0xDC00 + (code & 0x3FF);
+                out.extend_from_slice(&(high as u16).to_le_bytes());
+                out.extend_from_slice(&(low as u16).to_le_bytes());
+            }
+        }
+        Ok(out)
+    }
+
+    pub fn decode<Ctx: DecodeContext, E: DecodeErrorHandler<Ctx>>(
+        mut ctx: Ctx,
+        errors: &E,
+        final_decode: bool,
+    ) -> Result<(Wtf8Buf, usize), Ctx::Error> {
+        let mut out = Wtf8Buf::new();
+
+        while ctx.remaining_data().len() >= 2 {
+            let data = ctx.remaining_data();
+            let ch = u16::from_le_bytes([data[0], data[1]]);
+
+            if ch < 0xD800 || ch > 0xDFFF {
+                // BMP character
+                if let Some(c) = char::from_u32(ch as u32) {
+                    out.push_str(&c.to_string());
+                    ctx.advance(2);
+                } else {
+                    let pos = ctx.position();
+                    let replace =
+                        ctx.handle_error(errors, pos..pos + 2, Some("invalid character"))?;
+                    out.push_wtf8(replace.as_ref());
+                    // Don't advance here, the error handler already positioned us
+                }
+            } else if ch >= 0xD800 && ch <= 0xDBFF {
+                // High surrogate
+                if data.len() < 4 {
+                    if final_decode {
+                        let pos = ctx.position();
+                        let replace =
+                            ctx.handle_error(errors, pos..pos + 2, Some("unexpected end of data"))?;
+                        out.push_wtf8(replace.as_ref());
+                        // Don't advance here, the error handler already positioned us
+                    } else {
+                        // In partial mode, stop here and return what we have
+                        break;
+                    }
+                } else {
+                    let ch2 = u16::from_le_bytes([data[2], data[3]]);
+                    if ch2 >= 0xDC00 && ch2 <= 0xDFFF {
+                        // Valid surrogate pair
+                        let code = (((ch & 0x3FF) as u32) << 10) | ((ch2 & 0x3FF) as u32);
+                        let code_point = code + 0x10000;
+                        if let Some(c) = char::from_u32(code_point) {
+                            out.push_str(&c.to_string());
+                            ctx.advance(4);
+                        } else {
+                            let pos = ctx.position();
+                            let replace = ctx.handle_error(
+                                errors,
+                                pos..pos + 4,
+                                Some("invalid surrogate pair"),
+                            )?;
+                            out.push_wtf8(replace.as_ref());
+                            // Don't advance here, the error handler already positioned us
+                        }
+                    } else {
+                        // Invalid surrogate pair
+                        let pos = ctx.position();
+                        let replace = ctx.handle_error(
+                            errors,
+                            pos..pos + 2,
+                            Some("illegal UTF-16 surrogate"),
+                        )?;
+                        out.push_wtf8(replace.as_ref());
+                        // Don't advance here, the error handler already positioned us
+                    }
+                }
+            } else {
+                // Low surrogate without high surrogate
+                let pos = ctx.position();
+                let replace =
+                    ctx.handle_error(errors, pos..pos + 2, Some("illegal UTF-16 surrogate"))?;
+                out.push_wtf8(replace.as_ref());
+                // Don't advance here, the error handler already positioned us
+            }
+        }
+
+        // Handle remaining single byte
+        if ctx.remaining_data().len() == 1 {
+            if final_decode {
+                let pos = ctx.position();
+                let replace = ctx.handle_error(errors, pos..pos + 1, Some("truncated data"))?;
+                out.push_wtf8(replace.as_ref());
+                // Don't advance here, the error handler already positioned us
+            }
+            // In partial mode, just leave it for next call
+        }
+
+        Ok((out, ctx.position()))
+    }
+}
diff --git a/vm/src/stdlib/codecs.rs b/vm/src/stdlib/codecs.rs
index c0a091bcf8..a739886941 100644
--- a/vm/src/stdlib/codecs.rs
+++ b/vm/src/stdlib/codecs.rs
@@ -286,12 +286,12 @@ mod _codecs {
         delegate_pycodecs!(charmap_build, args, vm)
     }
     #[pyfunction]
-    fn utf_16_le_encode(args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        delegate_pycodecs!(utf_16_le_encode, args, vm)
+    fn utf_16_le_encode(args: EncodeArgs, vm: &VirtualMachine) -> EncodeResult {
+        do_codec!(utf16_le::encode, args, vm)
     }
     #[pyfunction]
-    fn utf_16_le_decode(args: FuncArgs, vm: &VirtualMachine) -> PyResult {
-        delegate_pycodecs!(utf_16_le_decode, args, vm)
+    fn utf_16_le_decode(args: DecodeArgs, vm: &VirtualMachine) -> DecodeResult {
+        do_codec!(utf16_le::decode, args, vm)
     }
     #[pyfunction]
     fn utf_16_be_encode(args: FuncArgs, vm: &VirtualMachine) -> PyResult {