iphone - OpenGL ES 2.0 texturing -

i'm trying render simple textured quad in opengl es 2.0 on iphone. geometry fine , expected quad if use solid color in shader:

     gl_fragcolor = vec4 (1.0, 0.0, 0.0, 1.0); 

and expected gradients if render texture coordinates directly:

     gl_fragcolor = vec4 (texcoord.x, texcoord.y, 0.0, 1.0); 

the image data loaded uiimage, scaled fit within 1024x1024, , loaded texture so:

     glgentextures (1, &_texture);     glbindtexture (gl_texture_2d, _texture);      glteximage2d(gl_texture_2d, 0, gl_rgba, width, height, 0, gl_rgba,          gl_unsigned_byte, data); 

width, height, , contents of data correct, examined in debugger.

when change fragment shader use texture:

     gl_fragcolor = texture2d (tex, texcoord); 

... , bind texture , render so:

     glactivetexture (gl_texture0);     glbindtexture (gl_texture_2d, _texture);      // unnecessary, defaults 0, completeness...     gluint texloc = glgetuniformlocation(_program, "tex");               gluniform1i(texloc, 0);      gldrawarrays(gl_triangle_strip, 0, 4); 

... nothing. black quad. glgeterror() doesn't return error , glistexture(_texture) returns true.

what doing wrong here? i've been on , on every example find online, doing am, , debugger shows parameters various gl functions expect them be.

after glteximage2d, set min/mag filters gltexparameter, defaults use mipmaps texture incomplete code.